The First

Ministry of Agriculture, Forestry and Fisheries, Japan
International Workshop on Genetic Resources

Root and Tuber Crops

Tsukuba Officeof MAFF Research Council
1994.3. 15‑17

Sponsored by

Research Council Secretariat of MAFF andNational Institute of Agrobiological Resourcesin cooperation with

National Agricultural Research Center,
Fruit Tree Research Station andJapan International Research Center for Agricultural Sciences

Contents
Page

Inaugural address
T. Takahashi

Welcome address
H. Fujimaki
Keynote address
The role of International Organizations in Root andTuber crops conservation
V. Ramanatha Rao, D. G. Debouck, and M. Iwanaga
Use of Root and Tuber Crop Genetic Resources in Japan
I. Shiotani

Session 1: Cassava
Genetic Resources Management of Cassava at CIAT
M. Bonierbale, C・ Iglesias, and K. Kawano
Physiological Characteristics of Cassava in
Southeast Asia
M. Oka, S. Sarakarn, and J. Limsila
Cassava Genetic Resources and Breeding in Thailand
C. Thiraporn, S. Sinthuprama, and S. Sarakam
Discussion
Session 2: Potato
Management and multiplication of Potato in Japan

A. Suematsu

Characterization, Evaluation and Use of Potato
in Japan

M. Mori
In vitro preservation of Potato Genetic Resourcesin NIAR
T. Ishige
Discussion

Session 3: Sweetpotato
Sweetpotato Genetic Resources in the Philippines
J.L. Bacusmo, V.Z. Acedo, A.M. Mariscal and M.Z. Oricion
Sweetpotato Genetic Resources and Breeding in JapanK. Komaki
Maintenance and Use of Sweetpotato germplasm in China
X.‑D. Guo, Y.‑H. Wang, J.‑Y. Wu and J.‑L. Sheng
Use of Sweetpotato Genetic Resources in Breeding in JapanO. Yamakawa
Sweetpotato cultivars bred for high yield and High Starchcontent in Japan

S.KatoDiscussion

Session 4: Taro and other root crops
Taro Genetic Resources and use in Indonesia
M. Diazuli
Root and Tubers crop genetic resources in Vietnam
T. V. Ho and collaborators
Characterization and Phylogeny of Taro Genetic Resources
in Japan

M. Hirai
Observation on Yam cultivation in Papua New Guinea
H. Toyohara
Discussion
General Discussion
Workshop summary
V. Ramanatha Rao
Closing Remarks
M. Nakagahra
List of Participants

INTRODUCTION
Preliminary address

Keynote address

Chairman
Kenkichi Sakai

Inaugural Address
TEIJI TAKAHASHI
Research Councillor
Secretariat Council of AFFRC, MAFF

Distinguished guests and participants.
On behalf of the Agriculture, Forestry and Fisheries Research Council, it
is my great pleasure to extend most sincere greetings and best wishes to all theparticipants in the ''MAFF International Workshop on Genetic Resources . This
workshop has been organised and sponsored by the Agriculture, Forestries andFisheries Research Council and the National Institute for Agrobiological Resourcesin collaboration with the Japan International Research Center for Agricultural
Sciences and the National Agriculture Research Center, Ministry of Agriculture,
Forestry and Fisheries.
I would particularly like to extend a warm welcome to our guests who have

travelled here to Tsukuba from different parts of Asia. We hope you will be
comfortable here in Japan and develop new research linkages with Japanesescientists.

Last year, Japan celebrated 100 years of agricultural research. The firstnational agricultural research station was established in 1893 in Nishigahara, Tokyo.
During the past 100 years genetic resources activities have supported basic
agricultural research and furnished invaluable materials for plant breeding. As a
response to the continuous and increasing need for the collection and preservationof genetic resources, the MAFF Genebank project was initiated in 1985.
Due to drastic changes in the global environment, the United Nations
Conference on the Environment and Development was held in Rio de Janeiro inJune 1992. The Convention on Biological Diversity which was one of the mostimportant outcomes of the conference came into force on December 29, 1993.
One of the basic objectives of the Convention is the "conservation of
biological diversity". It is in this role that the MAFF genebank project has played
an important part in meeting the Conventions objectives. The main objective of the
MAFF Gene Bank project is conservation of crop genetic diversity. It was with theimplementation of the Convention in mind that the Council decided to hold thisworkshop in order to contribute to the promotion of research and global strategies
for the conservation of genetic resources. Fostering increased interaction between
Japan and other countries, as well as the international agricultural institutes, in thefield of genetic resources conservation was another reason to hold this workshop.
I hope this workshop will be able to address important questions related toconservation, evaluation and use of root and tuber crops such as:

1. What are the main unsolved problems in conserving the different root
and tuber crops and how can they be addressed?.

2. How can international cooperation be fostered to provide comprehensive
conservation and evaluation of root and tuber crops?.

I would like to again express my cordial welcome to you all and hope thatyou all have a productive workshop.

Thank you.

Welcome Address
HIROSHI FUJIMAKI
Director General
National Institute of Agrobiological Resources

It is with great pleasure that I extend a warm welcome to all participantsof this Ministry of Agriculture, Forestry and Fisheries workshop on theConservation and Use of Root and Tuber Crop Genetic Resources. I would
particularly like to extend a special welcome to all those who have travelled a long

way to attend this workshop here in Tsukuba. We hope that the next few days will
make that journey well worthwhile.
I would like to acknowledge the contribution of several organizations. The
workshop was organised and sponsored by the Agriculture, Forestry and Fisheries
Research council. Here in Tsukuba to prepare for this workshop the National
Institute of Agrobiological Resources was helped by staff of the National
Agricultural Research Center and Japan International Research Center for
Agricultural Sciences.
The global concern for the conservation of, fast dwindling, genetic
resources requires an international approach to protect this fundamental genetic basefor humanity. Japan has in recent years significantly increased its commitment toconservation and evaluation of genetic resources. I would like to sight 3 examplesof this commitment:

1. In 1985 MAFF embarked on an ambitious project called 'The Genebank
Project' This did not just involve the building of a new genebank, it involves
hundreds of scientists from all over Japan and collaboration with scientists from allover the world in the conservation and evaluation of a multitude of crop, animaland micro‑organism genetic resources.
2. The Japanese International Cooperation Agency (JICA), a departmentof the Ministry of Foreign Affairs, has also had a project on the conservation anduse of genetic resources. This has focussed on helping other countries improvetheir ability to conserve their own germplasm. To date JICA has helped establish
genebanks in Bangladesh, Chile, Myanmar, Sri Lanka, and Pakistan. The National
Institute of Agrobiological Resources (NIAR) has assisted JICA in this project andparticularly helped provide training during the annually held training course which
has so far trained more than 100 scientists from 40 countries.

3. In the last decade of this century conservation and more particularly
evaluation and use of genetic resources is inextricably linked to advances made inbiotechnology. NIAR‑MAFF, 3 years ago, in cooperation with other institutes
began to unravel the secrets of the rice genome in what has been called the 'Rice
Genome Project'. This has rapidly resulted in rice becoming the most thoroughly
understood genomes of any crop. This project continues and can serve as a modelfor other genome projects. It is one of the aims of this project to enable new andvital genes from rice genetic resources to be rapidly moved to improved cultivars‑‑‑‑whether those cultivars be Japanese, Indian or Indonesian.
This workshop is planned to be the first in a series focussing attention on
particular groups of organisms vital to human welfare. Root and tuber crops havea number of characteristics which make them problematic to conserve, but on theother hand, these crops are among the most important in the world for the poorest
people. By bringing together experts in Asia, Oceania and from the CG systemhere to discuss conservation and evaluation of genetic resources of root and tuber
crops it is hoped that:a) a practical agenda for improving the conservation and evaluation of thesecrops may be formulatedb) cooperative research linkages will be established and improved.

Finally let me encourage you all to fully participate in the meeting. Pleaseask lots of questions and make full use of your time together.
Thank you.

KEYNOTE ADDRESS I
The Role of International Organizations in Root and Tuber
Crops Conservation
RAMANATHA RAO, V., DEBOUCK, D.G., and IWANAGA, M.
International Board for Plant Genetic Resources
Introduction

Root and tuber crops, including aroids, are main stays for millions of people
and occupy an important position in world agriculture. In contrast to the major
species, potato, sweet potato, cassava, taro and yams, there are about 100 root andtuber species of significance for agricultural or medicinal purposes. Most of these

may be important only locally, but play a significant role in the subsistence
economies and crop diversification. Root and tuber crop production has beensteadily increasing and in 1992 it was about 586 million MTs from about 478
million hectares (FAO, 1992). About 268 million MTs of potato were produced
from 180 million hectares, 128 million MTs of sweet potatoes from 92 million
hectares, 152 million MT of cassava from 15 million hectares, 27 million MTs ofyams from 2.8 million hectares, and 5.6 million MTs of taros from 9.9 million
hectares. The figures of production and area for other root and tuber crops are noteasy to compute. Nevertheless, these crops are very important in world foodproduction and for industry, fodder, medicines and in subsistence agriculture(Prescott‑Allen and Prescott‑Allen, 1990). Many so‑called minor species havegreat potential to become major crops, for example the material coming from theAndean region (Sperling and King, 1990).
Growth in agricultural production is not keeping pace with rapid population
growth, demanding increased production and diversification crops more than ever.
Roots and tubers can play a major role in addressing this issue. However, researchon these crops is usually not on the agenda of many national programmes (Lynam,1991).Therefore, there is a need for an international action on root and tuber

improvement and on conservation and use of the genetic resources. We present here
the status and challenges of conservation for root and tuber crops and someexamples of the work by some institutes, including that of the International Board
for Plant Genetic Resources (IBPGR), which is in now the International Plant
Genetic Resources Institute (IPGRI).
Present Status of Conservation

Now, there are many organizations involved in collecting and conservationof root and tuber crop germplasm. It will not be possible to go into detail at thespecies level, but the Table I attempts to summarize the existing collections aroundthe globe. There are about 135,000 accessions belonging to 22 genera/species
maintained in many organisations. The information provided here is from the
Directory of Root and Tuber Crops (IBPGR, 1986) and the actual figures currently
may be much larger. This is specially true for the minor species, such as theAndean roots and tubers and aroids on which there has been much interest in thelast five years (Arbizu and Tapia, 1992; Brucher, 1989; Rea, 1992) and manycollecting expeditions have been undertaken. The status of the root and tuber crops
collections in some international research institutes is provided later.
Challenges of Conservation and Use of Root and Tuber Crop Germplasm
Most of the root and tuber crops propagate by asexual means and theypresent unique challenges for conservation and use of their germplasm. Somechallenges are due to the effects of vegetative propagation on genetic diversity; theneed for different methods of conservation ‑ field genebanks, in vitro conservation,
cryopreservation and in situ conservation‑; the associated problems with eachmethod and need for balanced approach and safe movement of germplasm.

Table I. Some major and minor species of root and tuber foodcrops, total number of accessions and total number oforganizations with germplasm holdings.
Species No. of accessions No. of organizations
Alocasia spp.

231

18

Amorphophallus spp.

327

17

Arracacia spp.

418

6

Calathea spp.

6

3

Canna spp.

31

13

Coleus spp.
Colocasia spp.
Cyrtosperma spp.
Dioscorea spp.

54

6

5944

53

117

9

10661

53

Helianthus spp.

56

4

Ipomoea spp.

26020

83

Lepidium spp

6

1

Manihot spp.

25835

73

Maranta spp.
Mirabilis spp.
Oxalis spp.

78

11

16

4

Pachyrhizus spp.
Polymnia spp.

1317

7

364

17

42

3

Solanum spp.
Tropaeolum

60284

92

225

5

Ullucus spp.

471

5

Xanthosoma spp.

1035

41

Generally these are similar to those in other species, for example cereals. However,there are many specific differences that apply exclusively to roots and tubers (orbroadly to vegetatively propagated species) only. In addition, one can also consider,even if it is rare, conservation of true seed in conventional cold storage conditions.

Genetic Diversity
Agriculture might have begun, at least in some parts of Southern America,
with the harvest of roots or tubers, i.e. by the digging subterranean organs of wild
plants (Sauer, 1965), which was probably enhanced by the detoxification propertiesof clays (Johns, 1988). Archaeological records where available show indeed a long
history of crop husbandry of these species in that region (Hawkes, 1989). On theother hand, there is a clear tendency worldwide to prefer grain to root and tuber
crops because of differences in taste, status and quick postharvest deterioration of
the later (Heiser, 1990). In other words, root and tuber crops are often linked toprimitive agricultural systems in place for hundreds of years, consequently, incomparison to other crops, roots and tubers often harbour a unique genetic diversity
in landraces.
Understanding of the extent and distribution of genetic diversity in any genepool is basic for any conservation effort, and root and tuber crops are no exception.

While considering the issues in conservation of root and tuber crop germplasm, it
is important to point out some major differences between root and tuber crops andother groups of crops, e.g. grains. First, there is a basic delay in the processes
leading to meiosis and seed formation. The production of a thickened, edible organis also used as a propagule; so, seed fertility is not critical to the survival of thespecies. This delay encouraged farmers to collect and plant some of these thickened
organs. In such a system where biomass production is important and ploidy level
and heterosis can be maintained easily, farmers look carefully for specificgenotypes. Consequently, the factors that tend to affect the genome such as
mutations, transposable elements, and from time to time the full cycle of breeding
systems leading to sexual propagation, are the keys to understand the genetic
diversity structure, Such knowledge is essential for all operations in germplasm
conservation and use. It is important to understand reasons why farmers maintainmorphological variation and test it.
Second, structure of gene pools in root and tuber crops is still poorly
understood; perhaps with the exception of potato (both Solarium tuberosum subsp.
tuberosum and subsp. andigena; (Grun, 1990), for all other Neotropical root/tuber
crops, crop ancestry and place of domestication are still largely unknown (Table II
and III). While considering the development of any action for germplasm
conservation and use, one turns time and again to the following questions, whichhave heavy cost implications. Would one invest in in vitro conservation if one
cannot conserve genetically diverse material? Would one launch a large‑scale
breeding programme if one is not certain of the basic germplasm and its pertinent
information required for genetic progress?.

10

Table

II. Origin

Speciesand domesticationof American tuber crops

Wild ancestor

Place of domestication

Canna edulis
Dioscorea trifida
Helianthus tuberosus
Oxalis tuberosa
Solanum tuberosum
Tigridia pavonia
Tropaeolum tuberosum
Ullucus tuberosus
Xanthosoma
sagi ttifo li um
Sources:unknown
N South America
SE USA
Peru, Bolivia (?)
Bolivia,
Peru (!)
Mexico (?)
Peru (?)
Peru (?)

unknown

N South America

Arbizuand Tapia,
1992;
Brucher,
1967;
Chu
and
Figueiredo-Ribeiro,
1991; De Azkue and Martinez, 1990; Giacometti
and Leon, 1992; Grun, 1990; Hawkes, 1989; Heiser, 1969

Table EL Origin

SpeciesField

unknown
unknown (?)
known (?)
unknown
known (!)
not relevant (?)
known (?)
known

and domestication
Wild Ancestor

Apios americana
Arracacia xanthorrhiza
Bomarea hirtella
Calathea allouia
Ipomoea batatas
Lepidium meyenii
Manihot esculenta
Maranta arundinacea
Mirabilis
expansa
Pachyrrhizus
ahipa
Pachyrrhizus
erosusPachyrrhizus
tuberosus
Polymnia sonchifolia

not relevant
unknown
not relevant
not relevant
unknown
unknown (?)
unknown (?)
not relevant
known
unknown
known
unknown (?)
unknown

Sources:Noda, et al., 1992;
Sorensen, 1990; Zardini,Rea, 1992;
1991

of American root crops
Place of domestication
not relevant (SE USA)unkn own
not relevant (Chiapas,
Mexico)not relevant (Amazon)
unknown
not relevant (?); Junin, Peru
unknown
not relevant (Amazon)
unknown
unknown
Guatemala (?)
unknown
unknown

Reynolds,

et al.,

1990;

Sauer,

1993;

Genebanks
Due to the asexual nature of reproductionof most of the root and tuber
crops, it may not be always possible to conserve the germplasm of these crops inseed genebanks. So one method used, is to maintain them in field genebanks.
Though the field genebanks make the germplasm readily available for use, there aresomeproblems with them. Some of these include destruction by natural calamities,
pest epidemics,
number of plants to be maintained
and the high cost of
maintenance. Jarret and Florkowski (1990) considered conservation of germplasmof Ipomoea batatas. They compared the techniqueof conservationin fieldllgenebanks with in vitro conservationin terms of security, availability
and cost.
They concluded that in vitro conservation
was generally more secure and lessexpensive and labour intensive than maintenance in the field. One of the advantagesof field genebanks is the continuous opportunity
to evaluate and characterize
germplasm. There is no need to wait until crops emerge from prolonged juvenile
periods, as with in vitro methods. This is speciallytrue for perennial
species.
However, this does not apply to species like /. batatas. Vine cuttings may be
produced in less than eight weeks. The problem of somaclonal variation is notconsidered a major obstacle while genetic instability
is monitored regularly.
In vitro Conservation
Because maintenance of field genebanks is often problematicaland costly,in vitro conservation
is increasingly
being considered as the safer and practical
option for crops that produce recalcitrant
seeds or propagatedclonally (Withers,1991). Slow growth of shoot cultures offers a method of medium-term conservationcomparable to that of active seed genebanks. For the long-term conservation ofshoot cultures, cryopreservationin liquid nitrogen is becoming available
often.
Research has led to the development of some routine cryopreservation
protocols forcell suspensions,but fully differentiatedand complex structures, e.g. shoots andembryos, still present problems. In vitro techniques have a role to play at otherstages of the conservation process, such as for the distributionof germplasm or forthe collectionof samples from the field. For several crops, including
potato andcassava, most of the components of an in vitro conservation system are in place.
IBPGR and International
Center for Tropical Agriculture(CIAT) chose cassava fora pilot project to develop and test in vitro active genebank management procedures.
Much research is still needed in monitoring genetic stability
and ways of conserving
diversity
through in vitro conservation.
Florkowski
and Jarret (1990)
examined the relative
monetary costs ofdifferent
technologies
for conservation.
These methods included repeated field
planting
and propagation
every season, in vitro culture and cryopreservationoftissues or organs that can regenerate. They calculated
the costs per accession at$113.05
for in vitro culture, $128.00
for field collections
and $147.85
forcryopreservation,
based on 1,000 accessions.
In vitro and cryopreservation
technologies
offer the highest quality preservation
but the cost involved may require
repeated
evaluation.
Okoli (1991)
reviewed
the prospectof using in vitro
conservation to conserve the yam (Dioscorea)
germplasm.
Vitrification
may be an optimum method for cryopreservationof root andtuber crop germplasm. Vitrification
is a technicallysimplemethod forcryopreserving
plant germplasm, requiring
only the applicationof suitable
cryoprotectants
and rapid cooling rates (Towill and Jarret, 1992). The percentageof shoot tips surviving vitrificationand those subsequently
forming a shoot varied
widely among replications.
Many laboratories
around the world are undertaking
work on these lines of research.

12

Safe Movement of Germplasm
Root and tuber crops, propagating
vegetatively,
pose special problems not
only in collecting
and storing, but also from a germplasm health point of view. In
vegetatively
propagated crops, for example, viruses present in the mother plant will
inevitably
be found in derived vegetative
parts, such as tubers, roots, etc. In
cassava, the causal agent of bacterial blight, Xanthomonas manihotis, is present inthe xylem tissue of planting
material, and difficult
to detect. An example of afungal pathogen that is spread through tubers is the causal agent of the infamouslate blightdisease,Phytophthora
infestans.
Althoughoccurring worldwide
nowadays, it is of quarantine concern because of the existing physiologicalraces,
some of them being resistant to modern fungicides
such as metalaxyl. IBPGR has
played a significant
role in developing
guidelines
for safe movement of a few
important root and tuber crops germplasm (see under Role of IBPGR).
The Role of International

Organizations

It is certainly
a difficult
task to assign the 100 or so tuber and root crops
worldwide to a handful of researchers that are available
in the international
arena.
Additionally,
most of them work on three of the crops (potato,
cassava, sweet
potato),on the aspects of germplasm conservation,
germplasm enhancement andplant breeding. The story of the potato is illustrativein this regard (Hawkes, 1992).
The crop was held in high suspicion
till the 1800s in Europe, and now it ranks
fourth among the leading crops worldwide proving tremendous potentia. In mostcases, one would expect national programmes to take the lead in working on theseminor but potential
crops. However, this has not been the case in many instances(Lynam, 1991). Hence, it is important that the internationalorganizations
take upthe case for most of the root and tuber crops and assist national programmes intheir conservation and use.
The Role of IBPGR/IPGRI
Over the last 20 years, IBPGR has been closely associatedwith many
activities
related to conservation and use of root and tuber crop germplasm. Mostof these activities
have been carried out in collaboration
with different
national,
regional or international
programmes, including other Centers of the Consultative
Group on International
Agricultural
Research. IBPGR it self does not maintain any
germplasm, but it supports many national programmes in doing so. Some of these
activities
are highlighted
below.
Germplasm collecting
IBPGR has over the years supported germplasm collecting,includingthatof root and tuber crops. About 19 900 accessions of root and tuber crops have beencollected in IBPGR-supported
missions and the details are given in Table IV. For
example, since December, 1982, 5-7-day collecting
expeditions
each month13

Table IV. Summary of root and tuber crop germplasm
IBPGR missions
C oun try

N o. ofm ission scollected

through

Sp eciesl

N o . ofsam ples

4
2
4
7
1
1
2
1
3
7
2
4
1
1
6
2
2
1
3
1
1
2
1
5
21

M A N /S O I/U L U
PA C
A n dean tub ers/IP O /S O L
M A N /IP O
SO L
C O E /C O L/D IO /IP O
C O E /C O L/D IO /IP O /X A N
D IO
O X A /S O L
A n dean tub ers/IP O /M A N /S O L
D IO /M A N /X A N
D IO /M A N
C O L/D IO /IP O /M A N /X A N
IPO
A n dean tubers/IP O /S O L
D IO /A M N
C O L/D IO /M A N /PA C /X A N
XA N
A R A C E A E an d D IO /IP O /M A N /M A R /X A N
C O IVD IO /IP O /M A N
M A N
D IO /IP O
IPO
D IO /IP O /M A N /P A C /S O L /X A N
A LO O/S/AO ML O /C O L /D IO /IP O /X A N
IP

950
5
14 26
765
3
51
2 74
2
3 45
12 80
6
12 65
3 84
68
12 29
2 86
4 04
2
8 75
8
17
7
5
20 3
153 45

N ig eria
3
N epa1
2
P anam a
1
P aragu ay
1
P eru
10
P hilip pin es
1
P ap ua N ew
3
S ierra L eone1
S olom o n Islan ds 2
S ri L an ka
1
S u dan1
T hailand
6
U rugu ay
V en ezuela
2
Z aire1
Z am bia
4

C O L and oth er A raceae
C O L /D IO /IP O
D IO /M A N /M A R /X A N
M A N
A nd ean tubeis/IPO /M A N /S O L
A M O /C O L /C Y R /X A N
C O L /D IO /IP O /M A N /X A N
D IO /M A N /IP O /X A N
A L O /A M O /C O L/C Y R /D IO /IPO /M A N /X A N
D IO
IP O /S O L
A L O /C O L /D IO /IP O /M A N /P A C /X A N
SO L
D IO /IP O /M A N /X A N
C O L /D IO /IP O /M A N
D IO /IP O /M A N /PA C /S O L

16 2
52
14
2 10
45 0 5
31 5
85 4
134
344
33 9
7
98 3
32
29 1
148
49

A rg en tin a
B anglade sh
B olivia
B razil
B otsw an a
B urun di
B urk in a Faso
C am eroo n
C hileC olom b ia
C osta R ica
C ote d'lvo re
C uba
D om in ican R ep .
E cu adorG h an a
G uatem ala
H on duras
In don esia
L iberi a
M alaw i
M ali
M auritania
M exicoNM amalayibia
sia

Source:IBPGR Collecting
Database1 ALO Alocasia, AMO Amorphophallus,
CAN Canna, COE Coleus, COL Colocasia,
CYR Cyrtosperma,
DIO Dioscorea, IPO Ipomoea, MAN Manihot, MAR Maranta, OXA Qxa/is,
PAC Pachyrrhizus,
ULU Wuo/s, SOL Solarium, XAN= Xanthosoma

resulted in collecting
646 accessions of Colocasia,
239 of Dioscorea spp. and 528
accessionsof Ipomoea batatas in eleven states of peninsular
Malaysia.
The
accessions are maintainedin a field genebank for evaluation
and use (Hussain,1986).
Another example is the support for collectingof minor Andean root andtuber crops as reported by Castillo(1989).
In 1982, the National
InstituteofAgricultural
Research of Ecuador, supported by the IBPGR, initiateda collecting
expedition
to the Andean region. Several species including
Ullucus tuberosus,
Oxalis tuberosa, Tropaeolum tuberosum, Arracacia xanthorrhiza
and Polymnia
sonchifolia
were collected.
Besides supporting germplasm collecting,
IBPGR will shortly of publish (incollaboration
with FAO, IUCN and UNEP) a manual on germplasm collecting.
This
manual has chapters describing
the procedures for collecting
and transfer of root
and tuber crop germplasm.

14

Evaluation and documentation
Germplasm collections without data on their attributes
cannot be used to thefullestextent possible.
Such data can be generated only through systematiccharacterizationand evaluationof the material collected.
IBPGR has supported
many such efforts and helped the national
programmes in documenting
theinformation generated through such efforts. So far, we have publisheddescriptor
lists
on potato variety(in cooperation
with the Commissionof European
Communities)(IBPGR 1985), sweet potato (IBPGR,
1991), Xanthosoma (IBPGR
1989), Colocasia (IBPGR 1980) and Oca (IBPGR, 1982). Descriptors
for yam andArracacia are being developed.
As indicatedearlier, the Directoryof Root andTuber Crops was publishedin 1986 and efforts to update and revise it are underway. IBPGR supported the work on describing
and documenting root crops in theSouth Pacific,
which produced country catalogues
containing
descriptions
andevaluationsof root crop cultivars (Guarino and Jackson, 1983).
Safe movement of germplasm
IBPGR had, jointly with FAO, publisheda series of Guidelines
for the Safe
Movement of Germplasm. The importance given to root and tuber crops is
illustrated
by the fact that among the first ten issues four were dealing with root andtuber crops, namely "Edible
Aroids"(FAO/IBPGR,
1989),"Sweet potato"(FAO/IBPGR,
1989), "Yam" (FAO/IBPGR,
1989) and "Cassava" FAO/IBPGR,
1991). It is planned to develop, jointly with CIP, guidelines
for the safe movementof potato germplasm in 1995.
Current Programme
Presently, IBPGR-APO has a project entitled Improvement of taro and yam
resources', focusing on taro and yams. Aroids, including
taro, are important foodcrops of many parts of tropics.
Because they rarely enter into commerce, except
in local markets, it is difficult
to estimate their production.
Alocasia spp. andColocasia esculenta are important in South Asia, South East Asia and the Pacific.
Some types have special significanceas crops for difficult
lands, for they can
produce large yields under flooded or swampy conditions.
Yams are a staple foodcrop in many tropical countries of Southeast Asia and Oceania. As taro, these are
essentiallycrops of subsistence
agriculture.
The variationin taro and yams andrelated species is vast and have potential
not only as food crops but also forindustrial
and medicinal purposes.
In various consultations,
including RECSEA and SAC meetings, the priority
for action on taro and yam was identified.
So the Regional Office, finalizedaproject on of taro and yam resources which aims at improving the conservation andutilizationof yam and taro genetic resources in the APO region. Activities
under
this project include:
1. assess the status of taro and yam genetic resources in the
Pacific,
Southeast
Asia, South Asia and Oceania and collate the status report in
APO region from the information
gathered, 2. assist in formulationa network of

15

activities
on taro and yam genetic resource conservation, information exchange andimprovement, 3. assist in analysing
extant genetic diversity
and in developinginvitro conservation protocols and complementary conservation strategies,
4. assist in
carrying out ethnobotanicalstudies and 5. assist in virus detection and therapy forsafe movement taro and yam germplasm.
The assessment of taro and yam genetic resources in the APO region is inprogress, initiallyusing the work started by our New Delhi office in 1991. The
initial analysis indicatedhigh degree of interest and the need for enhancing genetic
resource activities
on these locally importantand difficult
species. Some of thenational programmes visited during the year have indicateda need to develop a
network of activities,
may be as a part of network of a major root crop such as
sweet potato. Future plans include promotion of studies on genetic diversity,in vitro
conservation,
development of complementary conservation strategies
and assistingvirus detection. The ethnobotanicalinformation that has been collected, mainly from
India, has been documented.
The Role of Other CGIAR Centers
Besides IBPGR, three other CG Centers are involved in work on root andtuber crops. These are International
Potato Center, (CIP) in Peru, International
Center for Tropical Agriculture(CIAT), in Columbia and International
Institute forTropical Agriculture(IITA) in Nigeria. Their work on root crop genetic resource
conservation, giving a brief picture on the status and activities,
is described below.
CIAT has the responsibility
for conserving cassava germplasm. It provides
a high level of security for conservation complete characterizationand evaluation,
documentation
and a system for effective pathogen-freeexchange of germplasm.
CIAT maintains the collection
in both in vitro and field genebanks. CIAT holds
5035 accessions in field genebanks and 4788 clones from 23 countries in vitro.
Duplicate identification
within the filed genebank is possible based on preliminarygrouping using biochemical
and morphologicaldescriptors
with high reliability.
A
conservation
strategy for cassava includes core collection
and duplicationin another genebank, in vitro and cryopreservation.
CIPTs potato genebank contains more than 15,000 accessions of cultivatedand wild tuber-bearing
Solanum species; over 13,000 samples represent native
Andean cultivars. CIP also maintains a collectionof more than 5,500 accessions of
Ipomoea; 3,200 are of /. batatas cultivars and 1,500 are of breeding lines, whileeight related wild species of section Batatas are represented by 800 accessions, withrecent collections
being incorporated(Austin,
1991,
Austin,et al.9 1991).
Additionally
there are 48 other species belonging to other sections. CIP is involved
in some collaborative
projects to conserve resources of minor tuber crops, especiallyof the Andean origin (Huaman, 1991). In the region, CIP has a major collectioninBogor, with more than a thousand accessions of sweet potato, collected mostly fromdifferent
parts of Indonesia. The collection
is in different
stages of morphologicalcharacterization.
Additional
collecting
in the eastern part of highland
Irian Jaya,

'on

16

efforts to eliminate
duplicatesin the collection
and developing
core collectioninBogor are planned (Dr. Jurg Schneider,1994. Pers. Comm.). Through the User's
Perspectivewith Agricultural
Research and Development (UPWARD),
CIP issupportingthe collection
and conservationof root crop germplasm and its
associatedindigenous
knowledge, with funding from Netherlands
and IDRC. In
order to explore ways to support existing conservationof both root crop cultivars
and indigenous knowledge
farm1, in situ sites were selected. Work is in progress
to look in detail at current conservation practices,
especiallythe relation between
diversityand management of planting
material over seasons (Dr. Gordon Prain,
1994.

Pers.

Comm.).

IITA

mandated crops include yam and cassava. Sweet potato wastransferredto CIP (Ng, 1991a).
About 1000 Dioscorea spp. and 2048 Manihot
species are conserved both in field genebanks and in in vitro. IITA is involved
with exploration,collecting,characterizationand other activities
on these four crops.
Research on in vitro conservation
is carried out and Ng (1991b)
describes
two invitro techniques
for the storage of root crop germplasm, a reduced growth storage
method for short to medium term storage and cryopreservation
for long term
storage. The first technique has been used widely to conserve root crop germplasm.
A total of 2,000 accessions of different
root crop species are maintained at IITA in
reduced growth storage.
Cultures can be maintainedfor 1-2 years before
subculturing.
The Role of Other Organizations
Numerous organizations,
including national, regional and international,
areactive in the area of root and tuber crop germplasm conservation
and use. It will
not be possible
to cover all of them here. So only a few examples are provided
below.
National programmes are the most important partners in any conservation
effort and it is true for root and tuber crops as well. Many national programmes arefocusing on the conservation of these crops, for e.g., collectingof potato genetic
resources in China began in the early 1980s. The total collection
now comprises
some 800 accessions, 123 of which are local varieties.
The collection
is maintainedin the field at the Research Instituteof Heilongjiang
Academy of Agricultural
Sciences. It is also maintained under low temperature and in in vitro conditions
atthe Instituteof Crop Genetic Resources of the Chinese Academy of Agricultural
Sciences (IBPGR, 1991). However, it must be noted that most of the efforts aremainly on major crop species.
As a regional programme, the Asian Vegetables
Research and Development
Center (AVRDC)
had within its genebank
1,6.71 form 32 different
countries(AVRDC, 1992). The collection
was maintained
as a field gene bank althoughmuch progress has been achieved on in vitro storage as well. In 1988, 6,710
meristems were excised from 1,116 accessions;those from 456 accessions were
cultured successfully(AVRDC, 1990). In 1991, AVRDC terminated its research on

17

sweet potato and transferred most of the germplasm to CIP. However, it should bepossible to consider other species in the future.
International
Development and Research Center (IDRC) of Canada has been
supporting national programmes to strengthen their research and development work
related to breeding and cultural management practices for cassava, sweet potato andother minor root crops (Dr. John Graham, Pers. Comm.). A component of this
support was directed towards a few germplasm related activities
and some African,
South American and South and South East Asian countries were recipientsof thissupport.
Following
the United
Nations
Conference on Environment
andDevelopment in June 1992, the focus of IDRCs programme and activities
has
shifted with explicit orientation
towards sustainable
and equitable themes and issues.
Under the biodiversity
theme, IDRC will support research on the development oftechnical,
social and economic interventions
that are appropriate
and necessary if
indigenous people and local communities, as key stakeholders,
are to participate
ina process that will allow for the conservation and use of our biologicaldiversity.
Considering
the need for increased attention on in situ conservationof many root
and tuber crops and their role at subsistence
farmer level, there should be somescope for support under the new policy. A recent example of this type is its support
to Vietnam through an IBPGR project.
Future Prospects
Some serious drawbacks for effective
conservation
and use of root andtuber crops are: insufficientknowledge on structure of genetic diversity
among genepools, the lack of investment in basic biology,
plant geography and short-sighted
collecting(i.e. focusing only on a few landraces and ignoring the gene pools as awhole). These drawbacks need to be urgently remedied. In other words, any
significant
effort to conserve the germplasm of root and tuber crops should passthrough genetic diversity
assessment of the materials in ex situ collection(s).
Thisshould, preferably,
be compared with what is still present in the wild or in the
farmers fields.
Any effort to be meaningful,it has to be interactive(back and forth,between ex situ and in situ germplasm collections)and should not be limited to asmall collection
at the local (national)
level. The effort should span but across genepools that most often means across national boundaries. A true international
effort,well in line with the Convention on Biodiversity,
will be required.
The studies on genetic diversity
will lead to the identificationof gaps indiversityand will help in the collectingof new diversity.
Such an effort will behelped by increased focus on ecogeographic
surveys in areas of diversity,and this
is particularly
significant
in the context of in situ conservation.
We must base ourplans on crop by crop in order to capture maximum diversity
and to put in place
the best conservation option. There is a general need to strengthen the evaluationand documentation
efforts in many national programmes. The international
and

18

regional organizations
can play a major role in helping the national programmes inthis matter.
The tendency to prefer grains to underground parts (Heiser,
1990) maycontinue into the conservation scene. This will be particularly
so if the process ofdomesticationof certain root and tuber crops is still incomplete.
This is especiallytrue if narrow, "economistic"
concept of plant genetic
resource conservation
prevails. However, in the recent past there has been a renewed interest due to theincreasing recognitionof economic and social significanceof root and tuber crops
in rural development. The increased interest in the cultivationof indigenous
species
by local communities further enhanced the interest in these crops. There is a needfor the conservation
community to capitaliseon this increased interest.
Roots and tubers offer a test for biodiversity
conservation:either we willsave them or we will loose the whole set. This way, there is the choice method ofconservation for roots and tubers: in situ. If the purpose is to conserve genotypes(some conservationists
may differ), as the method of propagation
is mostly asexual,
there will be hundreds and thousands of genotypes, both in cultivationand in thewild. Thus the conservation cost, especially
if in vitro approach is taken up, may
be enormous. Cryopreservation
is not the panacea to it, in the sense that several
developing
countries
have little or no access to that technology.
The term
cryopreservation
might also mean 'frozen without further generationof genetic
diversity1!
So, there is a need to pay increased attention to in situ conservation forroot and tuber crop germplasm. This should also consider the appropriatebalanceof field collections,where possible, to complement other methods and for ready use.
It should have component of in vitro conservation,
as a means for safe germplasm
transfer and for medium term conservation.
Cryopreservation
can be used, whenpossible,
as a safety back up. We also should look at the possibilityof seedconservation
in long term storage conditions.
We need to look for methods andlocationsfor flowering and fruiting
and seed productionin as many crops as
possible.
If seed can be produced and stored, we can conserve genetic diversity
aspopulations
for future generations.
To conclude,
this approach
would requirea more thoroughandmultidisciplinary
understandingof the genetic diversity,
agrocecosystems
and themethods that could be applied to the conservation of genetic diversity.
It will need
identificationof genetic diversity
rich areas and knowledge on the speed and/or
reasons of genetic erosion or absence of it. An example of such studies is the one
by Brush (1992).
These efforts to conserve and use the root and tuber crops better
will also need collaboration
at various levels, national and international.
This will
facilitate
for a successful complementary
conservationof root and tuber crops
genetic resources.

19

Acknowledgements
Authors wish to sincerely
acknowledge the assistance received from anumber of colleagues in the preparationof this presentation,
includingJulia Anne
Dearing, Marlene Diekmann, Luigi Guarino, Tom Hazekamp, Mark Perry, Ken
Riley, and Lyndsey Withers.
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KEYNOTE ADDRESS II
Use of Root and Tuber Crop Genetic

Resources

in Japan

ITARU SHlOTANIMie University
Abstract
The immeasurable value of plant genetic resources, represented by local cultivars of crops andtheir wild relatives,is now well accepted. Many leading experts from around the globe have joined
the present MAFF workshop to discuss commoninterests in root and tuber crop genetic resources andto exchange ideas. The author reviewed, as an example of the use of germplasm, results of the
programs for improving the starch yield in potato and sweet potato based on data from Japanese
centers for breeding. The release of modern varieties caused rapid replacement of local cultivars. The
significant
role of local cultivars in the past, present and future are discussed. Taro (sato-imo)andyams (yama-imo), crops integral to the Japanese traditional
diets, have not normally been subjected
to breeding.
They seem to be the only crops whose genetic resources are still well preserved in theform of local cultivars in Japan today. Recent basic research on these crops has revealed genetic
information on valuable traits for local agriculture.

Since the first regional meeting of the International
Board for Plant Genetic
Resources (IBPGR)
was held at the Universityof Tsukuba in 1980, genetic
resources issues have become of general interest,
and recent agrobiologicalapproaches on how to manage such genetic resources for agricultural
production
and people's welfare have been actively pursued in Japan. The activities
and recent
technical papers in root and tuber crops were well reviewed by Toriyama (1992).
Many leading experts of internationaland national projects have joined thepresent MAFF workshop to discuss our commoninterests on root and tuber crop
genetic resources. This workshop is an opportunity
to exchange information on thisimportant subject.
In this paper, I give examples of the extensive use of wild
species germplasm to improve yield, particularly
starch yield, in potato and sweet
potato in Japan. The significant
role of sweet potato local cultivars in the past isdemonstrated
and, further, their role as genetic donors to modern varieties
isdiscussed.
Finally, some recent studies on taro and yam are briefly reviewed fromthe viewpoint of their improvement.
.1. Improvementof Starch

Yield

in Potato

and Sweet Potato

There are some objectives commonin both potato and sweet potato breeding,and one such objective is to improve the starch yield of these domestic starch crops.
At present, cultivationof these starch producing crops is done at the northern andsouthern ends of Japan: potato production for starch is focussed in eastern Hokkaido

24and sweet potato starch

production

is concentrated

in southern

Kyushu.

1-1.

Potato breeding
The breeding program was conducted to generate cultivars superior to thecurrent leading variety Benimaru, released in 1938. The starch value of 16.5% of
this variety is not high when compared with values of more than 20% in recent
selections.
However, the outstanding
tuber yield of this variety has been favorably
received and now it is cultivatedon 22.7% of the total planted area, 67,300ha
in
Hokkaido based on a 1992 Survey. The other two starch-use varieties,
Eniwa(releasedin 1961) and Toyoakari (1986),
have not expanded in planted area andnowoccupy less than 3% of the total area.
A breeding projects in Hokkaido Natl. Agric. Exp. Stn. and Hokkaido Pref.
Konsen Agric. Exp. Stn. (HPKAES) developed the high-starchvariety Konafubuki
in 1981. With its starch value of 22-26% and appreciabletuber yield, the variety
gives a starch yield that is about 10% higher than that of Benimaru (Asama et al.
1982).
Then, Konafubuki is now planted on ll.4% of the total potato area.
As shown in the genealogic
map of Konafubuki(Fig. 1), the variety was
generated from a cross between high tuber yielding
Toyoshiro with al8% starchvalue and the low yielding
line WB66201-10
with an extremely high starch valueof 26%. The high-starchcharacteristicof this variety can be traced back to two
unique genetic resources, (1) the German cultivar Hochprozentige
having the starchvalue as high as 26%, and (2) the autotetraploid
Solanum chacoense and the S.

Figure.

1. Genealogic map of the high-starch potato variety Konafubuki that was generated in the
HNAES-HKAES programme from the cross between Toyoshiro of high tuber-yield
lineage and
WB66201-10
of high-starchlineage. The wild species S. chacoense in the autotetraploidandamphidiploidforms and the high-starch
cultivar Hochprozentige
were used to develop the highstarch lineage. Percent starch values are shown in brackets. Arrows indicate chromosome
duplication.

25

chacoense-S. phureja
amphidiploidline, E55164-18.
In the studiesoninterspecificcross-incompatibilityof Solarium species to potato, Irikura (1968)
succeeded in overcoming the cross-incompatibilityof diploid S. chacoense by using
either autotetraploidforms or S. chacoense-S. phureja amphidiploidforms asparents. Further, Irikura et al (1982) have reported the high-starchvalues of morethan 20 % shown by some accessions of S. chacoense to be an useful character.
These findings provided a basis of the use of this wild species germplasm for highstarch potato. On the other hand, in the Toyoshiro lineage, selections
2070-ab(32)and 3895-13
are both derived from introgressionof S. demissum which was
employed as a donor of resistance genes to late blight (Pytophthora
infestans).
There are some remarks on the traits other than its strach value of thisvariety.
Konafubuki was resistant to late blight as expected.
However, it turned
to susceptible
2-3 years after the release, and now the resistance of this variety topotato virus Y is attracted considerable
attention (M. Mori, personal communication).
Konahubuki
is susceptible
to potato
cyst nematode (Globodera
rostochiensis).
According to the 1993 Report of HPKAES, one new promisinghigh-starchline showing 23% starch value and resistance to the cyst nematode has
been generated from crosses involving the variety Konafubuki.
1-2. Sweet potato breeding
Improvement of starch yield is also a major objective
in sweet potato
breeding.
The program to improve cultivars by using wild species germplasm
started with interspecifichybridization
between a few cultivars and Ipomoea trifida
in 1957 at the Kyushu Natl. Agric. Exp. Stn. (KNAES).
Among the 20 /. trifida
accessions (K123), one accession (K123-ll,
19.6% starch content) with resistanceto two major Meloidogyne nematode pests provided
acceptableprogenies fromsuccessive back crossings with sweet potato parents.
From 1957 onwards, anumber of lines with high starch yield have been generated from the progenies inthe subsequent generations of the interspecificcross.
To examine the breeding effect of the /. trifida germplasm involved in theinterspecificcross with sweet potato, two groups of lines were compared in termsof their starch yield traits, starch content(%)
and root yield per are (kg/a).
Group 1:43 lines,

Kyushu 8 (selected

in 1943)

to Kyushu 57 (1965).

Group 2:28 lines,

Kyushu 58 (1965)

to Kyushu 101 (1991).

Measurements of traits were expressed by the values relative
to those ofstandard varieties
in the same yield-performance
tests of the KNAES breeding
program (Anonymous 2,3,4).
The Group 1 lines are those derived from crosses not
involving the wild species. In the trials of these 43 lines, high-starchvariety Norin
2 was used as a standard variety.
On the other hand, the Group 2 lines are thosederived from crosses involving the wild species. In this case, the standard variety

26

was Kogenesengan (KS), a more productive variety than Norin 2.
Frequency distributionsof lines are shown in two horizontal
axes, Norin 2axis (A) and KS-axis (B) in Fig. 2. Positioningof the two axes were determinedby using the measurements for Norin 2 and KS in the 1965-1966
performance tests
as described in Fig. 2. Comparisons between distributions
A and B in terms of root
weight and starch content, respectively,
indicate the following:(1)

Group 2 represents an improvement upon Group 1 for both yieldtraits,(2) about half of the lines in Group 2 exceed the KS level in root
weight,(3) most lines of Group 2 are beyond the KS level in starch content.
On this basis, it may be asserted that the breeding program which started withinterspecifichybridization
succeeded in changing the starch yielding
ability of sweet
potato. Among the lines in Group 2 are the variety Minami-yutaka (24% starchcontent, released in 1975) and the line Kyushu 79 (28.4%),
both lines have rootyields that are more or less at the KS level.
In addition,
there are other high-starchlines, not includedin the above
comparison, developed
from the same K123-related
lineagein the breeding
program of Natl. Agric. Res. Center (NARC). They are the varieties Shirosatsuma,
released in 1986 and having the starch content of 24.6% (Sakamoto et a/.,1989),
and Hi-starch, released in 1988 and exhibiting
starch content as high as 28.0%(Tarumoto et al 1989a),and the recently selected line Kanto 106, with 28.0%
starch content (Anonymous 1).
By assuming the starch content value of a newly released variety is thepotential
level of the breeding material of the time, an increment for starch content
per unit time was estimated.
The change in starch content from that of the variety
Norin 2 (21.4%,
1942) to that of the variety KS (23.9%,
1966) is 2.5% based on
the data from 38 trials carried out over 13 years at KNAES, which gives anincrease of 1.0% /10 years. As today's cultivars almost reach the 28% starch level,
the change from the variety KS!s level is about 4%. This gives again an increasein starch content of about 1.4%/10 years. The overall improvement in starch level
since the time of Norin 2 (1942) is about 1.0%/10
years. This increase has beenachieved by effective use of a wide range of germplasm resources including
a wildrelative,
native local cultivars,
local cultivars
and improved varieties from foreigncountries.
1-3. Starch as a future clean natural source
As a massive change in consumer behavior,starch consumption
hasdrasticallyincreased during the past decade. The total amount of starch supply rose
to almost 3 million
tons in the 1990fs.
However, the proportionof domestic
starches from potato and sweet potato has stayed a less than 20% of the total. On

27

Figure2. Improvement of starch yield using the wild /. trifida in sweet potato. Distribution(A)
includes 43 Kyushu selections,and distribution(B) 28 Kyushu selections
in crosses involving
the wild species. Root weight and starch content measurements were both expressed in values
relative to those of Norin 2 in distribution(A) and those of Koganesengan in distribution(B).
The two-headed arrow points to the value of KS in both distributions.
In distribution
A, thevalue of KS (root weight, 379kg/a=151;
starch content, 26.0%=112)
is expressed relative to thatof Norin 2 (251kg/a=100,
23.3%),
the standard variety of the Group 1 trial. In distribution
B,
KS is the standard variety, so it is assigned the value of 100.

28

the other hand, the amounts of imported raw starch from manioc, sago, corn, potato
and others have been rising over the past few years. This situation has hampered
domestic starch production,and triggered talks of a collapse in starch-use potato
or sweet potato production.
Any ideas and plans to lower the cost of agricultural
products by inputting
improved cultivars and other technology
seem impracticalbecause the price of domestic starches is about two to four times higher than importprices. Starch productionin Japan have some problems that need to be solved.assoon as possible.
From another perspective,
the potentialof starch as source of clean energy
is recognized.
Starch could help alleviatecurrent problems of environmental
pollutionarising from use of petroleum.
A survey by the Instituteof Energy
Economics, Japan has ranked alcohol fuels made from starch as an important energythat can be substituted
partly for petroleum.
Further, exploiting
biodegradable
polymers and plastics
is a remarkable subject with respect to the effective use of
agricultural
products, particularly
starches, in the MAFF Bio-Renaissance
Project
being conducted at present. In this project, Shiotani
et al. (1991)
and Asante et al.
(1993)
have proposed a breeding plan to improve the amylose component of sweet
potato starch by using their wild relatives.
In the near future starch supply-demand
for the Asian region will be watched by all the world. The root and tuber crop
improvement programs can play an active role in providing
a material base toresolve this global problem.
2. Local Cultivars

and Modern Cultivarsof Sweet Potato

2-1. The gain and loss
Replacement of traditional
local cultivars by modern varieties has often beenstressed and is called genetic erosion.- Based on MAFF Crop Statistics(Anonymous5, 6), replacementof local cultivars have occurred (Fig. 3). Percentagesof theareas planting
local cultivars(ALC) during the period 1940-91 are shown andsweet potato yields (kg/lOa)
during the period 1935-91 in this figure. The percent
ALC was 95.9% in 1940 and it had decreased to only 12.3% by 1955. In 1940,
4.1% of the sweet potato area was planted to three improved cultivars that weredeveloped in the early Okinawa breeding program prior to the full-scale
modernbreeding.
Two modern varieties, Norin 1 and Norin 2, were released in 1942, andsubsequently,
other released varieties found their way into remote farming villages.
The replacement of local cultivars was triggered by the release of these improved
cultivars, although food famine during and after World War II may have accelerated
replacement of local cultivars.
Another pronounced feature incidental
to the replacement
was a yield
increase: the average yield of 1300kg/10ain 1940 rose to 1900kg /10a in 1955.
The gain from increased yield and loss of traditional
local cultivars
are twisted
together in a thread. Fortunately,some native local cultivars from the early days
are preserved in the MAFF genebanks, 32 cultivars in NARC and 78 cultivars in29

Figure

3. Sweet potato local cultivars were rapidly replaced by modern varieties between 1940 and
1955. Since then, the percentage of area planted with local cultivars has been kept constant at
about 10%. The incidental
to the replacement was an increase in yield per unit area.

KNAES.

2-2. Local cultivars
being grown today
The percent area of local cultivars(ALC) has been nearly constant at the
10% level on average since 1955, but there is a great variationin the percentage
ALC among the prefectures.
The percent ALC and total area producing this cropin each prefecture
were illustrated
in Fig. 4 based on the Statistic
data in 1993
(Anonymous 6). Althoughno simple interpretationof this wide regional variation
seems to be possible,
only a lucid feature is that the percents are quite low in theprefectures
which have large shares in the big three, Tokyo, Osaka and Nagoya
Markets (1993 Market Survey).
These prefectures
are Kagoshima (0%ALC),
Miyazaki(5),Kumamoto (0) and Oita (0) in Kyushu, and Kochi (0), Tokushima (0)and Kagawa (0) in Shikoku,
and Ibaraki (4) and Chiba (18) in Kanto district.
Production in these districts have been conducted with their cultivation-post
harvestmanagement-marketingpackage plans.
Under the circumstances,
it is almost
inevitablethat only a few cultivars are carefully chosen to hold the marketability
such as standardized
size of root, excellent texture, high-quality
on a commercial
basis.
On the other hand, a high percent ALC is seen in a prefecture not known forthis crop, e. g., ALC isl00%
in both Aomori and Tottori, 74% in Miyagi, 63% inFukushima, 57% in Iwate and 53% in Aichi. At present there is a lack of detailed
information on local cultivars.
Among local cultivars is the high-quality,
table-use

30

Figure4. Great regional variation exists in percentage of area planted with sweet potato local cultivars(MAFF 1991 Statistics).
Some prefectures show a high percentage of more than 50%, whilemost major sweet potato producing prefectures (bold boxes) show zero or low percentages.

cultivar Beniaka which is cultivatedmostly in Chiba Prefecture and other districts.
However, most of these cultivars
are grown for home consumption by farmers.
Local cultivars are closely linked to the traditional
foods in every locality,thefollowingaccounts may illustrate
this: People of the fishing towns in Shima, thesouthern part of Mie Prefecture, have cultivated
two local cultivars (Hayato andHichi-fuku)
for dried sweet potato (kinko) as use as a winter food on their fishingboats and as well at home. Since the two cultivars have low yield, they have tried
to introduce new cultivars.
However, local people say, "Products made from anyother cultivars are not as satisfactorycompared with the ones from our cultivars".
The plan to commercialize
products made from their cultivars
started in 1957
among the farmer's group in cooperation with Ise-Shima Agriculture
Cooperatives,

31

and shippingof the product to the large city markets was realized for the first timein 1992. The next is the word of a woman who is in charge of managing "cropgenetic resources" in her yard. It was her reply to the inquiry about the source ofher sweet potatoes by Tarumoto et al. (1989b)
during a collection
trips for local
cultivars in Okinawa. She told them, " This was one I brought with me when I got
married, those were inherited
with this home, and I got that sort as a sweet one
from my neighbor ".
The ties that bind crops and humans may be strengthenedby mutualadjustment.
Crops adapt to the cultivationpressure by their phenotypic
adaptability
and genotypic change due to natural mutations and gene recombination
by somechance in southern districts,
while humans may use crops in different
ways as theirvarious uses become known. This co-adaptation,
operatingon a daily basis in
every farmer's yard, is not only a driving force to enrich genetic diversity
but also
a dynamic reservoir of cultigens.
2-3 Biodata of local cultivars
Noteworthy traits of sweet potato local cultivars
were quoted from theinspiring papers (Anonymous 2; Ono,1981;
Sakamoto, 1986). Nine native cultivars
cited in this report are familiar
to breeders as important ancestors of modern
varieties.
They are Beniaka, Genji,
Hayato, Hichi-fuku,
Oiran, Taihaku,
Table 1. Noteworthy traits of some local Sweetpotato cultivars
T ra it

L o c a l c u ltiv a r

C ro p m a n ag em en t
S pro utin g at a low tem peratu re (2 8‑c )B e n iak a
M o d erately h ig h tem p eratu re b etw een 32 ‑ an d 3 5 ‑c
O ir a n , T a ih a k u
E arly m aturity , y ield in g ab ility b y early cro p pin g
in g row th seaso n
Y o n ju ‑ n ic h i
L o w respo n se to n itrog en su pp ly , m o derate y ield
w ith o ut exc ess ve getative g row th
Y o n ju ‑ n ic h i
E x cellent sto rab ility
H ic h i‑ filk u , G en ii
R e sis ta n c e a n d T o le r a n c e
R esistan ce to b lack rot, C erato cy sti s fi m b riata
H ic h i‑ fu k u
R esistan ce to stem rot, F usa riu m oxy sp o ru m
H ic h i‑ fu k ll
f. sp . ba ta tas
T su ru n a sh i‑ g e n ji
H ig h resistan ce to ro ot‑ k n ot nem ato d e,
T a ih ak u ,Y o sh id a
M elo ido gy n e in cog n ita
M oterate re sistan c e to ro ot‑lesion nem ato d a,
H ic h i‑ fu k ll
P ra ty len ch us c off ea e
D rou g ht toleran ce
H lc h i‑ f u k u
T oleran ce to ex cess soil m oistu re
T aih a k ll
R o o t q u a lity
H ig h ‑ starch c on tent
H ic h i‑ filk u , G e nji
L ow p o lyp h en ol c on tent
B e n ia k a , T a ih ak u
L ow fru cto se and glu c ose a nd h ig h m alto se(steam ed ro ot) B e n ia k a
H ig h ‑ carotine co nten t
H a y a to

32

Turunashi-genji,
Yonju-nichi,
and Yoshida.
Most of the traits mentioned here
seem to be heritablecharacteristics,
and have been subjected to the will of breeders,and are still attracting
planner's concern in the creative breeding work for future
cultivars.
The traits and the local cultivars possessing
the useful traits are shown(Table 1).
A genealogic map show how local cultivars have taken part in the crossbreeding program. The first of the modern types, Norin 1 was a derived from across between two local cultivars,
Genki and Hichi-fuku.
With an increase in thenumber (n) of hybridizations,the number of the parents involved increased by as
many as 2n in the single-crosssequential
program. Consequently,
every recent
variety generally has a complex genealogy.
For example, the complete genealogic
map of variety Hi-starch (Fig. 5), released in 1988, includes a total of 66 original
entries from 14 parent stocks. The parent stocks involved in full-sib
and half-sib
matings were counted repeatedly.
The 14 stocks and their frequencies of entry use
in the Hi-starch map are shown (Table 2).
Out of 14 parents, seven cultivars
occupy 74.2% of the total entries,
indicatingthat they provided the major genetic background of this variety.
Amongthe native cultivars
having high entry values, Hichi-fuku,
Tsurunashi-genji
andYoshida were local cultivars
already mentioned for their noteworthy traits.
In conclusion,
I like to emphasize two points: (1) local cultivar germplasm

Figure5. Genealogic
map of the variety Hi-starchdeveloped from a wide range of genetic resources.
It comprises fourteen parent stocks, a wild relative, native cultivars,
local and improved cultivars
from foreign countries. Of a total of 66 entries, seven native cultivars (see Table 2) make up 49
entries(74.2%).

33

Table 2.

The parent stocks and their frequencies of use in thelineage of the sweetpotato variety Hi-starch
C u ltiv ar

F re q u en c y

N a tiv e cu ltiv a r
N a g o ‑ aran d a
K u rag aw a
C h o sh u
H ich i‑ fu ku
G enkiT su ru n a sh i‑ g en j i
Y o sh id a

5
5
1
14
8
7
9
S u b to tal

In tro d u c ed cu ltiv a r
B en ik aw a (C h in a)
K a leb e (U g an d a)
N o .2 2 9 (M e x ico )T .N o .3 (In do n e sia)
P elica n P ro fes so r(U .S .A .)W h ite S tar(U .S .A .)49

7 4 .2 0

7
1
1
1
4
2
S u b to tal

W ild r ela tiv e
Ip o m ea tr ifi d a (M Q x ic o )T o tal16

2 4 .2 0

1

1 .5 066

have an incalculable
value because they have a genetic background which makethem adaptable to the local climatic and edaphic conditions,and (2) breedingispartly trial and error, biodata including
characteristics
and genealogic
relationshipof the local cultivars provides a guid to make a reliable breeding plan.
3. Taro
According to the FAO Statistics(FAO, 1993), after China Japan has the second
largest taro production (20%) in Asia. This reflects the importance of this crop in
Japanese daily food.
Taros (sato-imo,village's
tuber) in Japan include Colocasia esculenta and
Xanthosoma sagittifolium.
Considerable
numbers of local cultivars of C. esculenta
are cultivated
all over Japan. It seems as if each farmer has his own cultivars.
Xanthosoma taros are occasionallygrown in areas of low soil moisture in Okinawa.
Genetic diversityof taros was studied by Tanimoto et al. (1986),
and theyreported that the isozyme analysis supported the previous classification
based onmorphologicalcharacters.
Mathews et al. (1992)
suggested
the phylogenic
connections of a few Japanese cultivars to certain cultivars in Nepal and to wildforms in northern Australia
based on the rDNA and mtDNA analyses.
Further,
Hirai et al (1989)
have stated, based on the corm-protein electrophoretic
patternanalysis, that most of the Japanese cultivars are most likely generated by mutations
in a few cultivars.
Effective
methods to improve cultivars are, of course, systematic breeding34

and mutation breeding programs. Recently, superior taro cultivars were developed
from a 15 year-progam based on sexually propagated populationin Western Samoa(Wilson et al, 1991).
Furthermore, genetic analysis of resistance to root rot blightcomplex in Xanthosoma taro was made in the diallel
cross design (Aguegua etal,1991).
These two reports suggest an effective
cross-breeding
method toimprove taro.
4.Yam
Japan is the largest producer of yam, showing 88% of the Asian total
production(FAO, 1993).
It used to be a symbol of the autumn harvest; however,today yams are available
all the year round in food shops. The majority of yam
cultivars (yama-imo, yama-no-imo, mountain's tuber) in Japan belong the species
Dioscorea opposita. Cultivatedthroughout
Japan, a great deal of genetic variation
exists as indicatedby numerous named or unnamed local cultivars.
D. alata is
supposedlya recent introduction
and restricted
to warm districts.
There is also awild relative, D. japonica, distributed
from all over Japan except Hokkaido.
Thiswild species
may become valuable
sources of genes for breeding
improved
cultivatedyamsto. Araki et al (1983)
studied cytologicallyand morphologicallytwo fertile male hybrids (2n=110)
derived from the natural cross betweem D.
opposita (2n=140)
and D. japonica (2n=80),
and they suggested the possibilityofdevelopinga cross-breeding
scheme to select seedling-derived
clones.
Recent studies by Nagashima et al (1985) have revealed marked differencesin properties
such as carbohydrate,
protein and mucilage content and amino acidcomposition
among four yam cultivars.
Further, Nagashima et al, (1990) indicateddifferencesin chemicaland physicalstarch properties
among the same four
cultivars.
Acknowledgment
I am grateful to Dr. Osamu Yamakawa, Kyushu Natl. Agric. Exp. Stn. and
Dr. Katsumi Komaki, Natl. Agric. Res. Center for their valuable suggestionson
sweet potato breeding,and to Dr. Isao Tarumoto, Directorof Kagoshima
Biotechnology
Institutefor his helpful advices.
Further I deeply appreciatedthekind guidance of Dr. Norio Murakami, Hokkaido Pref. Konsen Agric. Exp. Stn.
and Dr. M. Mori, Hokkaido Natl. Agric. Exp. Stn. The helpful criticism
of themanuscript by Mr. Nestor L. Pido is gratefully
acknowledged.
References
Aguegua, A., C.A. Fatokun, and S.K.Hahn,1991.
Genetics of resistanceto cocoyam root rot blightcomplex disease in Xanthosoma sagittifolium(L.) Schott. Abstract;
Ninth Symposium of theInternational
Society for Tropical
Root Crops, 1991, Ghana.

35

Anonymous 1, 1989, 1990 & 1991. 1989 Annual Report of Sweet Potato Breeding Laboratory,
No.l,
pp. 247. 1990&1991
ibid, No.2&3, pp.147, pp.177, Natl. Agric. Res. Center, MAFF. Japan.
Anonymous 2, 1972. Characters of the Sweet Potato Varieties and Breeding Strains. Research Report
43, pp.205, Kyushu Nat.LAgric. Exp. Stn, Fukuoka, Japan.
Anonymous 3, 1990, 1991,1992,1993.
Annual Report of Sweet Potato Breeding. No. 1, 1990, pp. 84;
No. 2, 1991, pp.ll;
No 3, 1992, pp.130; NO. 4, 1993 pp.131, Kyushu Natl. Agric. Exp. Stn.,
Fukuoka, Japan.
Anonymous 4, 1989, 1990, 1991, 1992. Annual Report of Sweet Potato Breeding. No. 1, 1989; No
2, 1990; No. 3, 1991; No 4, 1992, Kyushu Natl. Agric. Exp. Stn, Fukuoka, Japan.
Anonymous 5, 1950-1993.
Statistics
of Agriculture,
Forestry and Fisheries.
(Pocket edition),
Associationof Agriculture,
Forestry and Fisheries,
MAFF, Japan.
Anonymous 6, 1955-1981.
Statistics
of Sweet Potato Production
and Marketing,[1982-1993,
Statisticsof Root and Tuber Crop Production
and Marketing].
Upland Crops Division,
Agricultural
Production
Bureau, MAFF, Japan.
Araki, H, T. Harada, and T, Yakuwa, 1983. Some characteristics
of interspecifichybrids
between
Dioscorea japonica Thunb. and Dioscorea opposita Thunb. J. Japan. Soc. Hort. Sci, 52:153158.
Asama, K, H. Ito, N. Murakami, and T. Itoh, 1982. New potato variety "Konafubuki."
The Bulletinof Hokkaido Prefectural
Agricultural
Experiment
Station, 48:75-84.
Asante, S. A, T. Yamada, M. Hisamatsu, and I. Shiotani,
1993. Studies on the starch properties
ofdiploid
Ipomoea triflda (H.B.K.) Don. strains. Starch/Starke,
45:299-306.
FAO, 1993. FAO Yearbook Production,
1992, 46:103-104,
FAO Statistics
Series No. 112, Food andAgriculture
Organizationof the United Nations, Rome.
Hirai, M, T. Sato, and K. Takayanagi,
1989. Classificationof Japanese cultivarsof taro {Colocasia
esculenta (L.) Schott) based on electrophoretic
pattern of the tuber proteins and morphologicalcharacters. Japan. J. Breed, 39:307-317.
Irikura, Y,1968. Studies on interspecificcrosses of tuber-bearing
Solanums. 1. Overcoming crossincompatibility
between Solarium tuberosum and other Solarium species by mean of induced
polyploids
and haploids.
Research Bulletin of the Hokkaido Nat. Agr. Exp. Stat, 92:21-37.
Irikura, Y, Y. Nishibe, Y. Mitsui, and K, Shimizu, 1982. Classificationand characteristics
of wild
and cultivatedSolarium species. Chap. 2. Breeding by the Genome Manipulation.
p.59-61./«
Development of Cell-engineering
Breeding Methods in Crops and Application.
Research
Report 138, The Secretariat
of Agriculture,
Forestry and Fisheries
Research Council, MAFF.
Matthews, P, Y. Matsushita, T. Sato, and M. Hirai, 1992. Ribosomal and mitochondrialDNAvariation
in Japanese taro (Colocasia
esculenta L. Schott). Japan. J. Breed, 42:825-833.
Nagashima, T, T. Asari, I. Komai, and T. Obara, 1985. Study on Yam (Dioscorea batatas Dence).
Part 2. Differencesin viscosity
and suitability
for processing.
Journal of Agricultural
Science,Tokyo Nogyo Daigaku, 29:155-159.
Nagashima, T, and I. Komai, 1990. Some propertiesof starches from yam (Dioscorea).
NipponShokuhin
Kogyo Gakkaishi
37:124-129.
Ono, T, 1981. Characteristics
of Sweet Potato Cultivars. In Imo-rui Hen [ Root and Tuber crops],
Hatasaku-zenshu,
467-498, Nosangyoson Bunka Kyokai, Tokyo.
Sakamoto, S, 1986. Breeding approach against the injury by continuos cropping of sweet potato.
Recent Advances in Breeding 27:121-130,
Japanese Society of Breeding,Tokyo.
Sakamoto, S, T. Shiga, H. Ishikawa, S. Kato, T. Takemata, M. Umehara, and T. Ando, 1989. New
sweet potato cultivar "Shirosatsuma."
Bulletinof the Natl. Agric. Res. Center, 15:113, Tsukuba, Ibaraki, Japan.
Shiotani,I, A. Nishimura, S. Yamanaka, M. Taki, and T. Yamada, 1991. Starch propertiesof theI,

36sweet potato, diploid Ipomoea trifida (H.B.K.) Don. and tetraploidhybrids.
Starch/Starke,
43:133-138.
Tarumoto,
T. Shiga, S. Sakamoto, H. Ishikawa, S. Kato, T. Takemata, and M. Umehara, 1989a.
New sweet potato cultivar "Hi-starch." Bulletin of the Natl. Agric. Res. Center, 15:15-29,
Tsukuba, Ibaraki,
Japan.
Tarumoto, I. and H. Ishikawa, 1989b. Collection
and inventory of local sweet potato cultivars
inOkinawa Islands,
1988. 5:47-79, Annual Report of Exploration
and Introductionof Plant
Genetic Resources. National Instituteof Agrobiological
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Tanimoto, T. and T. Matsumoto, 1986. Variation of morphologicalcharactersand isozyme patterns
in Japanese cultivars of Colocasia esculenta Schott and C. gigantea Hook. Japan. J. Breed.
36:100-111.
Toriyama, K., 1992. Tuber and root crops, utilizationof plant genetic resources for crop improvement-Technical
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Wilson, J. E., P. Sivan, and C. Munroe, 1991. Alahua Sunrise and Samoa Hybrid improve thepopulationof taro {Colocasia esculenta [L.] Schott) in the Pacific. Abstract; Ninth Symposiumof the International
Society for Tropical
Root Crops, 1991, Ghana.

TECHNICAL

Session

1

CASSAVA

Chairmen
Shoii Miyazaki
Muhamad Djazuli

REPORTSGenetic

Resource Management of Cassava at CIATMERIDETH

BONIERBALE1,CARLOS IGLESIAS2

and KAZUO KAWANO3

Abstract
The responsibility
for the conservationof the genetic resources of cassava implies a
commitment to gather a representative
sample of overall diversity,and to ensure its long-term
availability
with low risk of loss, contamination
by pests or pathogens,or genetic modification.
Activities
includeacquisition,
maintenance,
description,
documentation,
distribution,and theidentificationand implementationof appropriate
conditions
and facilities
for long term storage of
germplasm. The base collection of cassava at CIAT consists of 5263 accessions representing
diversityfrom most cassava producing countries of the world. A core collectionof 630 accessions from thebase collection has been identified
to orient the agronomic evaluation and use of the germplasm. This
collection
provides the genetic base for cassava improvement at CIAT, and is shared through frequent
requests for material with certain characteristics
or adaptation for use in national breeding programs,
genebanks or advanced labs. To date, these activities
have been concentrated on cassava (Manikot
esculenta),
with more limited efforts in collection,
ex situ conservationand characterizationof thecrop's wild relatives.
The other important facets of CIAT cassava germplasm activity are the generationofadvanced breeding materials, their distributions
to national programs and the joint evaluation/selectionof superior cultivars with national programs. These have been frequently
described elsewhere; thus,
we present only a most illustrative
example in this text.

THE WORLD CASSAVA COLLECTION
Representation
and Acquisition
The basis for conservation and genetic improvement of cassava at CIAT is
the world collectionof 5263 accessions,comprised of entries from most of thecassava growing countries of the world. Representationin the base collection
isshown in Table 1. The majority of the accessions are from Latin America, whichis the primary center of diversity
for the crop. Within Latin and Central America,
gaps in the collection
are recognized
for Argentina,
Bolivia,
Haiti, Dominican
Republic, Nicaragua, Salvador and Honduras.

1 Geneticist,

CIAT Cassava Program, A.A. 67-13,

2 Gene Pool Breeder,

Cali,

Colombia.

CIAT Cassava Program, A.A. 67-13,

Cali,

Colombia.

3 Gene Pool Breeder for Asia and Coordinator,
CIAT Cassava Asian Regional
c/o Dept. Agr., Chatuchak, Bangkok, 10900, Thailand.

Program,

40

Table

1. Number of cassava accessions
genebank at CIAT.

by country of origin

o u n try o f O ri g in

To fo taa clcneussio
m bnesrmaintainedin the field active

L a st caotdCe IAa s sig
T n ed C

A r g e n tin a
B o liv ia
B r a z il
C o lo m b ia
C h in a
C o sta R ic a
C ub aD o m in ic a n R e p u b lic
E c uado r
F iji Isla n d
G u a te m a la
In d o n e sia
M a la y sia
M e x ic opN aign ea rim aa

16
3
12 8 8
200 8
2
147
74
5
1 17
6
91
51
67
100
4192

M A R G 16
M BOL 3
M B R A 138 6
M C O L 2 73 2
M CHN 2
M C R 149
M C U B 74
M DO M 5
M E C U 2 00
M F JI 6
M G U A 92
M IN D 5 1
M M A L 69
M M E X ll l
M NP AG NA 11399

P a ra g u a y
P e ruP h ilip p in e s
P u e rt o R ic o
T h a ila n d
U n ite d S ta te s
V e n e z u e la

19 2
40 5
6
15
31
9
24 0

M P A R 195
M P E R 6 15
M PH I 6
M P T R lO2
M T A I 31
M U SA 9
M V E N 3 32

E lite H y b ri d s‑ C IA T

32 9

S M 5 24 ‑1

TOTA L

52 63

As with all new accessions, the material will be introduced
to CIAT as invitro cultures,and tested for diseases
before becoming available
for field
characterizationand distribution.
The introduction
to the world collectionof nearly
800 accessions
from Brazil, currently
maintainedat the Centro NacionaldeMandioca e Fruticultura
Tropical (CNPMF),
178 new accessions recently collectedin the underrepresented
semi-arid ecosystem, of Brazil, and 165 new accessions
recently collectedin Argentina and currently kept at the Instituto
Nacional de
Recursos Biologicosdel INTA is in progress.
Landraces form China, Vietnam,
Thailand, and the Philippines
are among the priorities
for germplasm acquisitioninthe near future, in order to have good representationof the diversity
available
in
Asia.
The acquisitionof the most elite genotypes from the national breeding

41

program of Thailand provided 23 new genotypes to the world collectionin 1993.
The absence of a centralized
African collection,and quarantine problems withdiseasespresent on one continent
but not the other, have restricted
therepresentationof African germplasm. Current efforts by IITA to consolidate
information and collections
from regional cassava collections,
together with recent
advances in virus indexing will allow better representationof African germplasm
in the near future. To facilitate
the collection/acquisition
process, a series ofworkshops in the early 1980fs recommended procedures for the collectionof
cassava in the field, and elaborated a form which encourages the recording of data
critical to the eventual value and use of the collected germplasm (Gulick
et. al.,1983).
Several wild Manihot species are also maintained at CIAT both in vitro andin the field. Thirty species have been collected and introduced to CIAT, principally
as true seed. Problems with seed viability
and poor rooting of the more exotic
species, both in vitro and as vegetative
stakes have hindered conservation
efforts,
resultingin the current holdingof very few accessionsof each species.
Nevertheless,this collection
has provided some preliminary
results on root quality,
photosynthetic
characteristics
and pest resistance,
which are currently
being
confirmed by the Cassava Program, in parallel with efforts to expand the collection.
Conservation
Accessions of the world collection
are maintained both in vitro and in an
active field bank at CIAT headquarters
in Palmira, Colombia.
In the field bank,each genotype is classified
by its growth habit into one of three vigor groups, andplanted in two rows of three plants each. Spacing is 0.5 meters between plants and1.0 meter between rows, with 1.0, 1.5, or 2.2 meters between plots, dependingon
growth habit. This arrangement minimizes competition,
reducing the risk of losing
materials with poor adaptation, and ensures efficient weed control. Special attention
is paid to health status and to obtaining
a good stand, often involving replantingofindividual
genotypes.
As a working collection,
the field bank provides planting
material for experimental
purposesand enables direct
characterization
andevaluation.
The 18 month growing cycles for the field bank overlap in time toprovide security of planting material during the establishment
period. Each planting
occupies 4.5 hectares and another 4.5 ha is required for the overlapping
period.
The cost of maintenance and evaluationof the collection
is estimatedto beapproximtely
15 dollars per accession per cycle, 80% of which is labor. Thus, themaintenance of the field bank at CIAT/HQ is an expensive process needing 9.0 haof field area and the annual budget of US$90,000.
The in vitro collection provides safe duplicationof the world collection,in
an internationallyacceptable condition
for germplasm storage and exchange. The
culturesare maintainedin under slow growth conditions:
23±1°C constanttemperature with 1000-3000
lux illumination
during a 12H photoperiod
providedby cool white fluorescentlamps, at 70-90% relative humidity.
One to three plants

42

are grown in each 20 x 150 mm glass tube containing
a modified Morishige
andSkoog medium (Roca et. al., 1984) developed
at CIAT. Five test tubes of eachclone are routinely
maintained.
The need for periodic renovation of the culturesvaries among the genotypes conserved, but ranges between six months and two
years, with an average of 12 months. The cost of maintaining
each genotype invitro is estimated at 40 dollars (US). Procedures for acclimatizationof the cultures
to soil conditions
were described by Roca et. al. (1984)
in a manual which iscurrently being updated.
Germplasm requests for material in the collection
aredirected
to the Cassava Program, and are prepared and shipped by the Genetic
Resources Unit (GRU).
The Biotechnology
Research Unit (BRU) at CIAT has developed and begun
to standardize
techniques for cryopreservationof cassava shoot tips (Escobar et. al.,1993), which will provide a long term, low cost conservation
method to back up
the world collection.
Using a standard cultivar,
small shoot tips treated with apurified cryoprotectant
before immersion in liquid nitrogen,have proven mostviable.
The response of different
genotypes
to the steps of pre-conditioning,cooling,
and thawing are variable,
and further research is needed to determine
methods that will be broadly applicable
across cassava accessions.
Healthtesting
This process begins with observations
that should be made in the field at
the time material is identified
for entry into a collection(Lozano et. al., 1981).
Clones in the in vitro collection
at CIAT are subject to thermotherapy(40°C dayand 35°C night temperatures
on a 12 hour cycle for 3-4 weeks) and indexed forviruses and virus-like
diseases before they are declared eligible
for exchange.
CIATs Virology
Research Unit (VRU) has developed
or adapted sensitive
diagnostic
techniques for several diseases (Table 2), enabling the establishmentofpathogen tested cassava clones for conservation and exchange with the most up todate methods. Current research in the VRU addresses the improvement of methods
for health testing.
To date, 20% of the germplasm collection(and 80% of the corecollection)
have been indexed for the viruses in Table 2; and priority is being given
to the core collection(next section) for future indexing.
Further research is neededin the area of Frog Skin Disease, and efforts to produce and distribute
antisera foruse in national programs are global priorities.
Specific
guidelines
for the safe
movement of cassava germplasm have been prepared by FAO/IBPGR (Frison andFeliu, 1991).

Documentation
A relational database system (ORACLE v 6.0) used for management of the
germplasm collection
is maintained
and updated by the GRU and the Cassava
Program to organize information
relatedto all aspects of conservation
andassociatedareas, such as renovation, disease indexing, distribution
and passport
data. The database includes information on 5,040 accessions, with the facility
to43

Table 2. Virus and Virus-like Diseases and Assay Methods used in indexing cassava
collectionsat CIAT (ELISA = Enzyme-linked ammunosorbent assay; PCR =Polymerase chain reaction).

Figure1. Sample of information
fields in relational
database of cassava
germplasm at CIAT. Each column lists optional data fields
accessed through the area indicatedby the respective
arrow.

retrieve data in any one or a combination of various fields of information(Figure1). Twenty one morphologicalcharacters and 22 isozyme bands (esterase)
are used
to describe each accession, in addition to its basic passport data. Additional
data

44

on agronomic performance, taken on subsets of the collection
in experimental trials
complement the preliminary
description
in the database.
The in vitro and fieldcollections
are linked in the database,so that both field characteristics
andmaintenance information can be accessed simultaneously.
CORE COLLECTION
A sample of accessions, or core collection,
has been assembled at CIAT torepresent the genetic diversityof the base collection
in a more manageable size
(Hershey et. al., 1994). The core collection
was defined by the use of three specificparameters;
geographic
origin, morphologicaldiversity,and diversityof esterase
banding patterns, with approximately
100 accessions being added on an a prioribasis, to include material of importance to particular
breeding programs.
The
inclusion of isozyme diversity
as a selection criterion for the core was an effort toinclude a good representationof alleles present in the base collection,on theassumption that biochemicalmarkers are neutral traits with respect to selection and/or environmental effects. The base collection was stratified
by the three parametersof diversity
and random samples were drawn from the resulting
groups.
The
accessions in the core collection
and the parameters by which they were selected
are presented
in Table 3. The collection
is expected to be dynamic as aconsequence of the eliminationof duplicates,
acquisitionof new material, and bettercharacterizationof the genetic diversityof the genepool, including wild relatives.
The use of the core collection
by CIATs Cassava Program was recently
described by Iglesias et. al (1993).
This more manageable sample of the world
collection
can be evaluated across different
ecosystems and years in order todetermine the genotype by environment effects for important traits. A plan is being
developed for the safety duplicationof the core collection
with two institutions
outside Colombia;
likely candidates
to house the core collection
are EMBRAPA(Brazil),and Rayong Field Crop Research Center (Thailand).
This will provide
important characterization
data, and the first opportunities
for national programs to
use this large source of diversity
in their breeding programs.

CHARACTERIZATION
Evaluationof the core germplasm under field conditions
The core collection
has been used consistently
at CIAT to assess existing
genetic variability
for important agronomic characteristics,
and to indicate starting
points for more intensive evaluation
where promisingpreliminary
results are
obtained.
Several traits of importance for cassava breeding require highly specificand expensive evaluations,and are difficult
to apply to the entire germplasm
collection.
Among these traits are photosynthetic
rate, activityof C4 enzymes,
starch amylose/amylopectin
ratios, nutrient and water use efficiency,
quantitative

45

Table

3. Accessions

includedin the core collection

according

to different

parameters.

N u m b e r o f c lo n e s fo r d istin c t p a r a m e te r s
O rig inBA orglive niatin a

G oe origg rainp h ic

M ivgoic
dlo
erprsalhityo‑eD steivo rafe r sesity

seA lepcrtio
io nrisinnF uinmcaoblreer

21

42

0

3

38

B ra z il
C h in a
C o lo m b ia
C o sta R ic a
C ub aD o m in ica n R e p u b lic
E c uado r
GF ijiu a te m a la

10 0

13

15

20

10 1

1 11
9
10

15
7

13
5

14
4

14 6
23
18

25
81

6
06

0
0

4
2

32
1 25

In d o n e sia
M ea xlaicy sia
o

1 48

60

01

26

21 05

P ana m a
pP ea ru
ra g u a y

62 35

108

3

27

74 60

pP uh eilip
rt op inR ic
e so

1

20

20

42

72

T h a ila n d
U n ite d S ta te s
V e n e zu e la

41

9

3

3

55

0

3

5

27

33

440

100

51

121

630

C IA T c lo n e s
IIT A c lo n e s
TOTAL :

levels of cyanogens, resistance to diseases and pests, and others. To orient thisevaluation,a series of testing sites in Colombia has been identified
as "ecologicalhomologues", corresponding
to the major edaphoclimaticconditionsof cassava
production regions of the world (Hershey, 1984).
A descriptionof the importantecozones is presented in Table 4, with reference to the respective
testing sites,
homologous production regions, and principal
biotic and abiotic constraints.
The
core accessions are evaluatedin selected field sites each year to contributemorphologicaland agronomic data, and as a source of germplasm for the
ecosystem-oriented
improved genepools developed by CIAT.
Duplicate

identification
An important considerationin the management of any germplasm collectionis the minimizationof duplicate accessions, whose maintenance consumes valuable
resources with no return. The strategy currently being applied
at CIAT to the46

Table 4. Descriptionof edaphoclimatic

zones defined by CIAT Cassava Program for germplasm

development.

Not all constraints

are found in all regionsof a given edaphochmaticzone.

identificationof duplicatesin the cassava collection
relies on the database ofcharacterization
information,and consistsof three steps:
1) First, candidate
duplicatesare identified
by screening the data base for accessions with identicalcharacterization
data, including morphologicaldescriptors
and isozyme patterns. 2)
As the morphological
data often results from activities
conducted on distinct partsof the collection
in different
years, it is necessary to grow the putative duplicates
togetherside-by-side
in the same year,
and repeat the morphologicalcharacterization
process.
3) Finally,
when the number of putative duplicatesisreduced, the remaining groups are characterizedwith a molecular probe, M13

47minisatellite,
which assays many regions of the genome at thesame time,presenting
a highly discriminatory"fingerprint"
for each genotype.
Together withthe preceding
data, the fingerprint
is consideredsufficient evidence to confirm
duplication(Figure2). According to the level of duplication
so far detected,
it is
expected that around 600 accessions could be eliminated from the collection,savingFigure2. Analysis of putative duplicatesin the cassawa collection
by molecular fingerprinting.
DMAfrom pairs of accessions
with similar morphology
and isozywe pattern is digested
with Hae III, and Southern blots are probed will a cloned
sequence from the bacteriophage
M13.

48

considerable

resources in germplasm conservation.

DEVELOPMENT OF ADVANCED BREEDING MATERIALSThe role of CIAT could be limited
to the collection,
evaluation,
maintenance and distributionof basic germplasm materials if the research capacityof all the national programs were satisfactory.
However, the research capacity inmany tropical countries is far from this and it was necessary that CIAT upgraded
the immediate
usefulnessof germplasm materials to be offered to national
programs. Thus, the development of advanced breeding materials has been themost important undertakingof the germplasm-related
research at the CIAT Cassava
Program. We have been frequently
reportingthis (e.g. Kawano et al. 1990,
Kawano 1992; also see CIAT Annual Reports from 1973 to 1993 and cansummarize as follows.
This started with the enhancement of basic physiologicalyield capacityof the breeding
population
at the CIAT HQ in the 1970s andaccomplisheda 100% increase in the yield capacity of the breeding
populationcompared with that of the original unselected population
thanks largely to improved
harvest index.
A simultaneous selection
in a high stress environment added
tolerance to numerous diseases and pests as well as adaptation
to infertile
and acidsoils. The more decentralized
breeding program conducted by CIAT/HQ during the
1980s and thereafter
added further adaptations
to specificedapho-climaticconditions
and resistances to specific diseases and pests to the breeding population.
The population
improvement at the Field Crop Research Center by the CIAT/Thaicollaborative
program further upgraded the total biomass production, root dry matter
content and tolerance to drought of the breeding population.
We consider that thecurrent CIAT cassava breeding materials provide national program breeders withimmediate selection opportunities.
DISTRIBUTIO

N

Germplasm from the core collection,or from CIAT hybrids involving moreadvanced generations,is freely available
to interested
programs as true seeds,
indexed meristem cultures or disease indexed stakes.
National programs withcapacity to handle and evaluate true seed progenies frequently request controlledoropen pollinatedfamilies from parents adapted to their needs and this has been themost frequently used means of germplasm transfer. Advanced labs, or genebanks
are more likely to request clones as in vitro cultures.
A third form of germplasm
distribution
stems from the availabilityof selected elite clones as stakes from
disease-indexedmother plants. This method simplifies
handling of the material by
the recipient,
but is recommended only for countries with homologous disease
spectrums. Training is available
at CIAT to national program scientists
in thetransfer, maintenance, and subsequent utilizationof cassava germplasm. Table 5
illustrates
the pattern of germplasm distribution
over the past ten years, in terms of49

Table 5. Cassava germplasm distribution
R eg io nsh
T yp
ip me eno ft

by CIAT during 1984-1993.
shipm
N o . enof t

clo n es/N ofam. ofilies

T o tal N o .

A fricaInd exed stakes
B o tanInvitricalo p lantlets
seed

182

1701772 7 65 0848

A sia

Ind exed stakes
B o tan
In
vitro
ical
p lan
seed
tlets

1
110
38

6
5 44
4 662

54
3 2 28320847

L atin A m erica

Ind exed sta kes
BIno tanvitro
icalp lan
seed
tlets

18
115
60

19 8
2 94
6 132

155 4
181129137 28E u rop e

Ind exed stak es
In
B o tanvitro
icalp lan
seed
tlets

1
20
14

13
16
14 07

78
4 20
2 175 05

N o rth A m e rica

Ind exed stak es
BInotanicalvitro p lantlets
seed

23
19

77
99

132805 03

type of material, and destination.
The amount of genetic variability
this way to Asia should far exceed all the genetic variability
which
before.

UTILIZATION

transferedinexisted there

BY NATIONAL PROGRAMS

Aside from genetic resources, an efficient research network with national
programs is another important asset of CIAT. Through this network, we have been
distributing
advanced breeding materials, working hand in hand with the national
program breeders and, most importantly,
producing results.
Much have beenreported on this process (e.g. Kawano, 1994) and we can appreciate an example ofgood collaboration
with a strong national program in the other paper from Thailand
to be presented in this Workshop. We present here only the most illustrative
case
for the utilizationof advanced breeding materials by national program.
Cassava research in Vietnam had been isolated for a long period of timeand systematic
introductionof cassava germplasm did not take place until ourcontact with their research program. A spectacular yield and root dry matter
content upgrading followed after the introductionof selected clonal materials fromthe Thai-CIAT collaborative
breeding program in 1989 (Fig. 3). This yield jumpreflects the progress accumulated through the breeding work by the Thai breeders
and our collaborative
breeding work in the past 20 years. One of the best clones
in this scheme is now being officially released for all over Vietnam, the 22nd CIAT

50

Fig

3. Change
and rootin themean of breeding

dry matter

content

population(allat Hung Loc Research

entry

mean in yield

Center,South

trials)in fresh

root

yield

Vietnam.

relatedcultivar officiallyreleased by the national programs in Asia.
The network collaboration
functions as a significant
source of feed-backinformation.
Recently, we have been identifying
several officially
recommended
cultivars
showing excellent results also in other countries with different
climatic
conditions.
This may indicate the potential
for broad adaptationand stability
acrossvariable environmental
conditions.

PRIORITIESFOR FUTURE RESEARCHMANAGEMENTFOR CASSAVAIN GENETICRESOURCE

Several areas of cassava production, particularly
in sparsely populated areas
where the crop is of primary importance,
and in areas of traditional,
small plot
cultivation,
have not yet been subject to systematiccollection
or conservation
efforts.
Wild relativesof cassava are still poorly represented
in germplam
collections,the improvement of which will require collection
and of conservation
techniques,
probably including a combination of ex situ and in situ methods. Threats
to local diversity,
including the expansion of modern agriculture
and social change

51

or instability
in these areas contribute to the urgency of collecting
and conserving
cassava genetic resources.
Another subject in need of future effort is that of our understandingof thedistribution,
generation, and maintenance of genetic variabilityof the crop genepool
in the field situation.
Related to this is improved knowledge of the ecologicalandgeographic
distributionof the cultigen and its relatives,
and the taxonomic andcytogenetic
relationsamong them. For example, the involvement of Manihot
species in the evolution of cassava is not yet clearly understood,
and despite thetremendous amount of morphologicaldiversity
among cassava genotypes, the extent
of a founder effect (Ladizinsky,1985) for the crop is not yet known. Basic studies
in genetics,
biochemistry,morphology,
ecology and biogeography
are needed tocontribute to concepts of interspecificrelationships,
and the distributionof diversity
within and among different
components of the genepool.
Crossabilityof exotic
accessions with the cultigen and subsequent characterizationof hybrids for fertility/ viability
define the limits to genetic exchange, providing
informationon thefeasibilityof use of diversity
by breeders. The value of wild relatives lies in someof the adaptive
charactersthey possess, as potential
sources of variationforcharacters of limited range in the cultivatedgenepool, and, for the unknown valueof potential
combinationsof alleles from cultivatedand exotic sources, which may
result in heterosis
or transgressive
segregation
for critical
traits (deVicente
andTanksley, 1993).
The genetic resources of cassava will be of greater value if a global
database of collection
and characterization
data is developed.
These area has been
given high priority
by the Manihot Genetic Resources Network, which is in theprocess of defining a 'minimum descriptor list' and a common database system tobe shared among members. In the future, new methods such as molecular andaccompanying
statisticalanalyses
will be valuable
in achieving
objective,
quantitative
measures of genetic diversity,
not affected by environmental
conditions,for application
to sampling strategies
for germplasm conservation and use.
REFEREN CES
DeVicente,

M.C. and S. Tanksley.
1993.
QTL analysisof transgressive
segregation
in aninterspecificcross of tomato. Genetics.
134: 585-596.
Escobar, R.H., W.Roca, and G. Mafia. 1993. Cryopreservationof cassava shoot tips. pp. 166-121.
In: Roca, W. and AM. Thro (eds.).
Proceedingsof the First International
Scientific
Meetingof the Cassava Biotechnology
Network. Cartagena, Colombia.
CIAT, Cali, Colombia(Working Document no. 123).
Frison, E.A. and E. Feliu (eds.).
1991. FAO/IBPGR Technical guidelines
for the safe movement of
cassava germplasm. FAO Rome. IBPGR Rome. 48 pp.
Gulick, P., C. Hershey, and J. Esquinas-Alcazar.
1983.
Appendices
III and IV. In: Genetic
resources of cassava an wild relatives.
IBPGR Secretariat,
Rome.
Hernandez Romero, Luis A Evaluation de nuevas variedades
de yuca con la participationdeagricultores/asesoria
cientifica,
Jacqueline
Ashby, Qair Hershey, Carlos Iglesias.
CentroInternationalde Agricultura
Tropical OAT, 1993. (Documento de Trabajo No. 130).

52

Hershey,

C, C. Iglesias,
M. Iwanaga and J. Tohme. 1994.
Definitionof a core collectionfor
cassava.In: Iglesias,
C. and M. Iwanaga (eds).
Proceedings
from an International
Workshopon Cassava Genetic Resources.
August 1992.
Cali, Colombia, OAT/IITA/IBPGR(inpress).
. 1984. Breeding cassava for adaptation
to stress conditions:
Development of a methodology.
In: CIP (Centro Internationalde la Papa).
Proc. 6th Symp. Inte. Soc. Trop. Root Crops.
lima, Peru. pp. 303-314.
Iglesias,
C, M.W.Bonierbale, M. El-Sharkawy, C. Lozano., A. Bellotti,
and C. Wheatley.
In press.
Focusing basic research for cassava variety improvement. Proceedingsof the International
Society on Tropical Tuber Crops 6-9 November, 1993. Trivandrum, India. Central Tuber
Crops Research Institute,
Kerala, India.
Kawano, K., S. Sarakarn, A. limsila,
A Tongglum and D. Suparharn.
1990. Cassava cultivar
evoluation
viewed through harvest index and biomass production.
202-209. In: R. Howeler(ed.). Proc. 8th Symp. Internaitonal
Society for Tropical
Root Crops. Bangkok, Thailand.
Kawano, K. 1992. CIAT cassava germplasm and its role in cassava varietal improvement in Asia.
170-184. In: R. Howeler (ed.). Cassava Breeding Agronomy and Utilization
Research in
Asia. Bangok, Thailand.
Kawano, K. 1994. "Green Revolution"and cassava breeding.
In press. In: R. Howeler (ed.) Proc. IV
Asian Cassava Research Workshop, Trivandrum, India, Nov. 1993. CIAT, Bangkok,
Thailand.
Ladizinsky,
G. 1985. Founder effect in crop-plant
evolution.
Econ. Bot. 39(2):191-199.
Lozano, J.C., A. Bellotti,
J.A. Reyes, R. Howeler, D. Leihner, J. Doll.
1981.
Field problemsofcassava. Cali, Colombia.
OAT. 208 pp.
Roca, W.M.,J.A. Rodriguez, G. Mafia and J. Roa. 1984. Procedures for recovering cassava clones
distributedin vitro. CIAT, Cali, Colombia.
8pp.

Physiological
LIMSILA2 MTSUNORI

Characteristics
OKA1, SUPACHAIof Cassava in Southeast

Asia

SARAKARN2 and JARUNGSIT

Abstract
Cassava is one of the most productive crops in dry regions having infertile
soils. Most
cassava is grown in unirrigatedfields without fertilizers
in the main areas of production in Southeast
Asia with pronounced dry periods. Dry matter production varies markedly from season to season. Thechange in productivity
between the rainy and dry seasons, is closely correlated with the changes inleaf canopy. Physiologicaland morphologicalcharacteristicsof leaves were studied in relation to dry
matter production. Plant characteristics
related to yield, such as plant type, sink- source balance andgermination ability, were further investigatedusing Thai local and newly released cultivars including
QAT hybrid clones. Yield stabilityof cassava can also be achieved by selecting germplasm well
adapted to the local conditions,as well as by improving cultural practices which lead to sustainableproduction.

In troduction
Cassava (Manihot esculenta Crantz) originatedand was domesticatedinSouth America more than three thousand years ago. From South America cassava
spread to Africa and in 18 to 19 century to Asia (Leon, 1977). Among tropicalcrops, cassava has great potential
as a source of carbohydrates.
Further increases
in cassava productivity
may be expected from cultivar development and improved
cultural practices(Cock, 1985, De-Vries et al., 1967 and Kawano & Jennings,
1983). Cassava is the fourth most important crop in terms of dietary calories forhumansJ Asia produces nearly 35% of the worlds total productionof cassava. In
Asia, Thailand,
Indonesia and India are the major producers (Table 1). Average
cassava yield in Southeast Asia is about 13t/ha compared to the world average of
lOt/ha. Yield, however, varies considerablyfrom country to country. Yields inThailand,Indonesia and China range from 12 to 15 t/ha.
The unique characteristicof cassava is its ability to be highly productiveindry soil with low fertility(Howeler,1981).
Generally
cassava is grown in
unirrigatedfields and without fertilizers
in tropicalareas with pronounced dry

Divisionof Research Information,
Japan International
Resreach
Agricultural
Sciences(JIRCAS),
Tsukuba, Ibaraki 305, Japan
Rayong Field Crops Research
Rayong 21 150, Thailand.

Center, Field

Crops ResearchCenter for

Institute,

DOA,

54

Table 1 Cassava root production,
harvestedsoutheast Asian countries.
C o u n tri e s

P ro d u c tio nl.O O O M t 1,

A sia
T h a ila n d
In d o n e sia
In d ia
C h in a
V ie tn a m
P h ilip p in e s
A fri c a
S o u th A m e ri c a
C en tra l A m e ricaO c ean ia

5 1 ,2 3 7
2 1 ,13 0
16 ,3 18
5 ,2 0 0
3 ,3 5 8
3 ,0 0 0
1,3 2 070 ,4 4 4
2 9 .3 4 3999
194

W o rld T o ta l

15 2 2 1 8 .

Source:year book 1992.

FAO production

area and yield for selected

H a rv ested area
OOOha

Y ie ld
t/h a

3 ,7 8 8
1 ,4 4 2
1 ,3 3 3
247
231
278
160
9 ,3 0 3
2 ,4 5 3
196
27S

H 5
14 .7
12 .2
2 1 .1
14 .6
10 .8
8 .3
1A
12 J l5A
IO 8

1 5 /75 7& 2

periods.
Under adverse conditionsof acid, infertile
soils with a long dry season,yields of 15 to 20 tons of fresh roots can be expected. Factors responsible
for lowyields in Southeast Asia has been identified
as poor agronomic practices, low soil
fertility,
absence of fertilizer
use and, probably,
the use of local cultivars.
To
increase and stabilizedcassava yields, improvement both in agronomic practices andcultivars is desirable.
This report deals with the growth characteristics
and several
other physiologicalfactors related to yielding
ability.
The experiment reported were conducted in the Southeast Thailand between
the Rayong Filed Crops Research Center, Thailand and the Tropical Agriculture
Research Center, Japan, during 4.5 years from 1983 to 1987.
Growth Characteristics
At the onset of the rainy season cassava sprout easily and leaves expand.
About 3 months after planting,
dry matter weight of the whole plant markedly
increases with vigorous growth and development of the leaf canopy (Fig. 1). Leaf
area index (LAI) reaches to 3 to 5 by the middle of the rainy season and ismaintained throughout the season. During this period, while maintaining
high LAI,
crop growth rate (CGR) shows a maximum rate of 15 to 20g/m2 day. With theonset dry season, leaves are dropped, and LAI and CGR decreases rapidly. Cassava
continues to produce leaves even in the dry season. The leaf production
rate,
represented
by the leaf number produced per apex and per day, decrease to
0.05/apex
day compared as 0.8 in the rainy season. Single leaf area is only 20%of that in the rainy season (Table 2). Leaves again expand leaves and dry matterproduction
picks up again with the coming of rainy season.

55

Fig. 1

Cassava growth pattern observed in Thailand in rainy and dry seasons.
Note: *Numerals in the upper figure show monthly rainfall (mm).

Table 2.

Difference in physiologicalcharacteristeicsof leaf canopy
between rainy and dry seasons in Thailand

56

The annual growth pattern is shown for a representative
sample of cultivars
growing In Northeast Thailand which has a pronounced wet and dry seasons (Fig.
1). In Insular of Southeast Asia, such as Indonesia which have a short dry season,
cassava also shows the similar growth pattern. Dry matter production of cassava isclosely correlatedwithleaf development
and maintenance. It is importanttomaintain the developed
leaf canopy throughout
the growing cycle for high dry
matter and root production(Cock et al., 1979).
There are large differencesin physiologicaland morphologicalcharacteristicsof leaves produced in the rainy and dry seasons (Table 2). As alreadymentioned, cassava expands lots of large leaves in the rainy season. Leaf nitrogencontent (mg/g) on a dry matter basis of leave is significantly
higher in the rainyseason than in the dry season. On the other hand, nitrogen and chlorophyll
content,
given on leaf area basis (mg/dm2), show no significant
difference
between seasons.
Leaves are thicker in the dry season. Observationsof stomata on the abaxial
surface show significant
difference
in stomatal density between seasons. Leaves inthe dry season show xeromorphism, characterized
by the small thick leaves and thedevelopment of a thick wax layer on the leaf surface (Fig. 2).
The photosynthetic
rate of single leaves follows an asymptotic curve withincreasing
light
intensityand saturates
with the maximum rate of about
27mgCO2/dm2h. The maximum rates for cassava are within the range of 23 to
30mgCO2/dm2h (Palta, 1984) and are not high compared with those of major crops,
such as rice, maize, sugercane which have rates of 35-70 mgCO2/dm2h. During therainy season, the rate changes around 25mgCO2/dm2h
in daytime. On the other
hand, the rate in the dry season decreases to one-third of that in the rainy season
in parallel with the decrease of transpiration
rate and stomatal conductance (Table
2). Judging
from the comparisonsin the physiologicaland morphologicalcharacteristicsof leaf canopy between both seasons, significant
total dry matter
increase can not be expected for the storage root productionin the producing areas
with a pronounced dry season lasting for 6 months. Therefore, it is importanttoselect the appropriate
cropping seasons and cultivars to achieve high root yield.

Fig*

2

Comparisonof abaxial

leaf surface

in rainy(left)and dry(rigit)

seasons*

Note; The length of bar shows 100 and 10 /an in the left and right figures? respectively*

57

The onset of root bulking occurs about 3 months after planting
with thedevelopment of the leaf canopy and the maximum increases of root weight
coincides well with the period of maximum dry matter production (Fig. 1). Largeamounts of photosynthate
are translocatedto the roots with the progress of growthand starch content of root become to be above 30% at harvest time in the dry
season. Cassava shows the highest caloric production per hectare and per year due
to high root yield (De-Vries
et al., 1967). The high annual economic yield in
cassava is associated with the maintenance of LAI and CGR close to the maximum
for long periods and with the high rate of translocationof photosynthateto roots.
Cultivars

and High Yielding

Ability

Traditional
cultivarsof cassava show genetic variation
for growth
characteristics
and yielding
ability.
CIAT (1974) reported a ten fold difference
inyield among 2,500 traditional
cultivars which were collected from the Central andSouth America, and high yielding
cultivars generally were associated with highharvest index, represented
by the ratio of root weight to total weight. Among the
cassava genetic resources, CIAT accession number MColl684 showed high yielding
abilityand harvest index.
In tropicalAsia, as in the American tropics, there are many traditionalcassava cultivars,
used mainly for fresh human consumption, that have beencultivatedon a small-scale
for a long time (Table 3). These cultivars,
such asGolden Yellow in Philippines,
and Kretek in Indonesia usually have low harvest
index. Other traditional
cultivars for large-scale production,such as Black Twig in
Malaysia, Lakan in the Philippines
and Rayong 1 in Thailand show moderately highyielding
ability and harvest index (Kawano, 1988). The selection of Rayong 1 fromThai local cultivars
is considered
to be one of the most important factors in the
successful productionof cassava in Thailand.
High yielding
cultivars
show a high harvest index, as observed bycomparing yields among many traditional
cultivars (CIAT, 1975). During varietal
Table

3.

Traditional

and promisingcassava cultivars

in SoutheastAsia

C o u n tri e s

T ra d itio n a l
cu ltiv ars

P ro m isin g
cu ltiv a rs

C h a ra cteristic s ofp ro m isin g c u ltiv ars

T h a ila n d

R ay o n g l

R ay o n g 36 0

HH ig
ig h HY I, &H I starc& starch , Eharlin, E arlin
es s es s

In d o n e sia

K retekA d ira 4l *HH ig h Ysta,rch
H I,&L ostarc
w H hC N , E arlin e ss

P h ilip p in es

KG ao dldabe na oY ello w

VC oClom‑ 1 b ia

H ig
ig h Y & H I

Source: Howeler(1988)
and Kawano(1988)*Edible type, HLharvest index, Y:root yield,
M ala y sia

B la ck T w ig

C ‑5

HCN:xyanide

content

H ig h Y & starc h , E a rlin e ss

58

improvement of cassava, it has become evident that harvest index is the mostimportantindicator
for selecting
high yielding
cultivars(Kawano, 1990). We
investigatedthe plant types which were observed in Thai local and CIAT hybrid
clones in relation to dry matter and root production.
They could be classified
into
4 main types according to the branching habit (Fig. 3). High yielding
cultivars andclones belonged to the non- branching type with 3 or 4 stakes per plant (B type)and sparse branching type (Cl type), The two plant types were characterized
by 3
to 10 apices with short stakes. Both types appears to be ideal for achieving highyield in view of the balance between biologicalyield and harvest index.
At present, many promising cultivars have been released in Asia. Theyshow high yielding
abilityand harvest index while having other good agronomic
characteristics,
such as high starch, early harvestability
and low cyanide content ofroots (Table 3).

Cultivationand Sustainable

Production

Cassava planting materials are taken as long stakes obtained from the stemsof plants which should be 8-12 months old and free of diseaseso7 3 or pests.
Before planting,long stakes kept under the shade of trees for a while are cut into
cuttings of 15 to 20 cm length with sharp knife. They are planted verticallyin mostcountries
except in china, Malaysia
and Philippines
where they are planted
horizontally.
Planting density is around lm between cuttings in the major producing
areas of southeast Asia.
Successful germination in one of the most important factors for production.
It depends upon the quality of cuttings and the growing conditions(Cock, 1985).
Variation in germination
ability
is considerable
among cassava cultivars.
For
example in Thailand,
Rayong 1 has a higher germination
abilitythan Rayong 3
under moisture stress. The characteristics
of cuttings related to germination
andFig. 3Major plant types of cassava observed
CIAT hybrid clones.

in Thai local

cultivars

and

59

subsequent survival were investigatedusing Rayong 1 and 3 in the rainy and dry
seasons. Multiple regression analysis showed that the major factors controllingthesurvival rate included the volume density, fresh weight and volume of cuttings in
the dry season and volume density in the rainy season. Thus, the volume density
was the main determinantof successful germination
for both seasons. Volume
density can be used as a useful indicator
for the qualityof planting
stakes andbreeding criteria (Oka et al., 1987).
Cassava can be planted all year round even in regions that have distinct
rainy and dry seasons. However, there is an optimum planting time for achieving
the highest yield depending
upon the local conditions.
Timing of planting depends
on many factors, most important of which is the onset of the rains. Most cassava
is planted early in the rainy season or late in the rainy season and harvested during
the dry season in major producing areas of Southeast Asia. In Thailand also mostcassava is plantedin the early rainy season in April and May, but a large
proportionis also planted at the end of rainy season in October to November. The
plantings
in both seasons can produce high yields, since they lead to large leaf area
throughout
all the growth cycles, especiallyduring the rainy season (Oka et al.,1987).
Cassava has the ability to grow and give moderate yield under very low
fertility
conditions
where no other crop can be grown beneficially(Howeler, 1981).
Cassava can tolerate low calcium, nitrogen and potassium in the root environment
better than other crops and has the ability
to produce bulked roots at low
phosphorus levels. At the same time, cassava is also known as a crop that exhausts
soil nutrients. However, Howeler (1981)
noted that cassava does not exhaust soil
more than other crops. Cassava extracts large amounts of potassium and, to lesser
degree, nitrogen from the soil. There are many reports that emphasize
theimportance of potassium are nitrogen in achieving high root yields (Cock, 1985.
Howeler, 1981 & 1988).
In general fertilizer
use is very low in Southeast Asia except in cassava
plantationsin Sumatra,Indonesia,
and Malaysia and in some areas in Java (Howeler,
1988). In Thailand
fertilizer
is rarely in farmers' field because of the high price offertilizer,
although farmers know its importance. Recommended amount of fertilizer
depends upon the country and soil fertility.
Howeler (1988)
concludedthat
generally in Southeast Asia nitrogen, phosphorus and potassium is recommended
within the range from 50 to 100 kg per hectare. In our trial with the fertilizer
use
on a gray podzolic soil with sandy texture in Thailand,
the uptake of nitrogen,phosphorus
and potassium per hectare and per year was 154, 35 and 93kg,
respectively.
Even in this trial with the applicationof fertilizer,
only the uptakeof potassium
showed a significant
effect on increasing
root yield and it isconsidered
to be a more important element than nitrogen under less fertile soil
conditions
in Southeast Asia.
It has been found that soil productivity
has steadily
declined in long-term
cultivationof cassava without fertilization.
In the trials in the northeastern
and

60

southeasternparts of Thailand,yields decreased
from nearly 30 to 18 t/ha,
indicatinga rapid initial loss of fertility
in the first 15-20 years of continuous
cassava production (Sittibusaya
et al., 1988). Long-term sustainableproductivityof cassava can only be maintainedby preventing
soil exhaustion
through thejudicious
use of fertilizers,organic manures, green manures, or intercroppingwithgrain or tree legumes, and by preventing soil erosion or degradation
through theloss of organic matter (Howeler, 1988).
Conclusions
Cassava had distributed
throughout
the tropics including
southeast Asia
from the originalareas in South America, because it produces
large amounts ofstarch but also well tolerate low soil fertility
and long dry periods.

1.
2.
3.
4.

The growth characteristics
of cassava can be summarized as follows;High and stable productivity
under low and medium-input condi-tions.
High resistanceto diseases and pests and tolerance to adverse soil andclimatic conditions.
Easy propagation from stakes.
Large variations
in cultural practices in cassava based-cropping
systemswith other crops and trees.

The root yield of cassava under commercial conditions obviously depends
on the levels of management and inputs. Using the present cultural practices the
fresh yield can be expected to be within the range of 20 to 30t/ha even in adverse
soil and climatic conditions.
Cock et al. (1979) stated that the potential annual yield
could be 90t/ha when cassava is groWn under ideal growing conditions.
There are many cassava cultivars which are well adapted to various growing
conditions
and different
cropping systems in the tropics. The genetic diversity
within cassava for physiologicaland characters needs to be clarified
so thatgermplasm which meets breeding objectives
is readily available.

Acknowledgement
The authors wishes to express their sincere gratitude
to Mr. Sophon
Sinthuprama,
Director and Mr. Charn Tiraporn, Root Crops Specialistof the Field
Crops Research Institute,Thailand, for their support for the research reported. Deep
thanks are also due to Dr. Tomoaki Matsuda, Professor of the Ibaraki University,for valuable discussion
on the morphologicalcharacteristics
of cassava leaves.

61

References
OAT 1975. Cassava production
systems in OAT Annual report 1974. 54-109. Cock, J.H. 1985.
Cassava - Newpotential for a neglected
crop. Frederik A Praeger Publisher,
Colorado,
USA ppl91.
Cock, J.H. 1986. The agronomic potentialof cassava for the upland areas of tropicalAsia. Pages
203-212. In Cassava in Asia, its Potential
and Research Development Needs: Proceedingsof a Regional Workshop held in Bangkok, Thailand, 5-8 June 1984. OAT & ESCAPCGRPT Center, Cali, Colombia.
Cock, J.H., Franklin, D., Sandoval, G. and Juri, P. 1979. The ideal cassava plant for maximum yield.
Crop Sci. 19:271-279.
De-Vries, C.A., Ferwerda, J.D. and Flach M. 1967. Choice of food crop in relation to actual andpotential
productionin the tropics. Neth. J. Agri. Sci., 15:241-248.
Kawano, K. 1988. OAT cassava germplasm development in Asia - Cooperation with national
programs. Pages 117-129. In R.H. Howeler & K. Kawano (eds),
Cassava Breeding andAgronomy Research in Asia. QAT, Cali, Colombia.
Kawano, K. 1990. Harvest index and evaluationof major food cultivars
in the tropics. Euphytica
46:195-202.
Kawano, K. and Jennings, P.R. 1983. Tropicalcrop breeding - achievements and challenges.
Pages
81-99. In Potential
Productivityof Field Crops under Different
Environments. IRRI, Manila,
Philippines.
Howeler, R.H. 1981. Mineral nutrition
and fertilizationof cassava, QAT, Cali, Colombia, pp52.
Howeler, R.H. 1988. Agronomic practices
for cassava productionin Asia. Pages 313-340.
In R.H.
Howeler & K. Kawano (eds),
Cassava Breeding and Agronomy Research in Asia. CIAT,
Cali, Colombia.
Leon, T., 1977. Origin, evaluation,and early dispersalof root and tuber crops. Pages 20-36. In J.H.
Cock et al.(eds),
Proceedingsof the Fourth Symposium of the International
Society for
TropicalRoot Crops. OAT, Cali Colombia, 1-7 August 1976, IDRC, Ottawa.
Oka, M., limsila, J., Sarakarn, S., Sinthuprama,
S. and Tiraporn C. 1987. Eco- physiologicalstudies
on cassava(Manihot
esculenta Crantz) in Thailand.
The final report of the cooperative
research works between Thailand and Japan. pp241.
Palta, J. 1984. Influence of water deficienton gas exchange and the leaf area development of cassava
cultivars.
J. Exp. Bot., 159:1441-1449.
Sittbusaya,
C, Nakaviroj,
C. and Tunmaphirom, D. 1988. Cassava soil research in Thailand.
Pages
145-156. In R.H. Howeler & K. Kawano (eds), Cassava Breeding and Agronomy Researchin Asia. OAT, Cali, Colombia.

Cassava Genetic

Resources and Breedingin Thailand

CHARN TfflRAPORN1, SOPHON SINTHUPRAMA1,SUPACHAISARAKARN2,WATANAWATANANONTA2, CHAREINSAK ROJANARIDPICHED3
and KAZUO KAWANO4

Abstract
Thai cassava production and processing industry heavily depends on the export market.
With the anticipatedremoval of preferential
tarif treatment to the Thai tapioca importation
to themajor market EC, an export ceiling and more competitive price may be imminent to Thai cassava
products.
Thus, the general Thai cassava policy is to reduce the cassava planted area and increase
the productivity.
To respond to this situation, cultivars with higher yielding capacity and better quality
roots are required.
To achieve this goal, creating broad genetic variability
through germplasm
introduction
from abroad, recombining desirable characters with local cultivars and selecting superiorclones may be the most promising approach.
Only a small number of local cultivars
existed in Thailand
and the current germplasm
collection consists of mostly introduced clones, cultivars or seed selections from the foreign countries
especiallyfrom OAT, Virgin Island and Indonesia.
The hybridizations
and selections
based on thisgermplasm have achieved the official release of seven cultivars as of now; five from the Departmentof Agriculture
and two from Kasetsart University.
These new cultivars are characterizedby higher
yielding
capacity, high harvest index, higher root starch content and early harvestability.
For further
improvement, Thai cassava researchers will emphasize on selecting higher biomass, yield, root dry
matter content while maintaining the high harvest index.

Introduction
Cassava is a promising crop for the tropic as a source of carbohydrates
because it is very efficientin converting solar energy into carbohydrates,
can begrown in a diverse range of conditions,and can be harvested over an extended

1 Field
Crops Research
Bangkok, Thailand.
2 Rayong Field

Institute,

Crop Research

Department

Chatuchak,Center, FCRI, DA, Rayong 21150,

3 Department of Agronomy, Faculty
Bangkok, 10900, Thailand.
4 CIAT Cassava Asian Regional
Thailand.

of Agriculture,of Agriculture,

Kasetsart

Thailand.

University,

Program, c/o FCRI, DA, Chatuchak,10900,

10900,

Chatuchak,Bangkok,64

period of time. Although it is not a staple food for the Thai people, cassava is acash crop produced by a large number of small farmers in Thailand and nearly all
the production
is processed
into animal feed components or starch. In 1992
Thailandexported 9.1 million tons of cassava products, earning US $ 1139.1
million. About 95% of the total production
is exported, mainly as pellets (89%),
followedby starch (8%) and chips (3%).
The most important market is theEuropean Community, amounting to 5.48 million tons in 1992. Domestic use is
only about 5% of the total production
and is utilized as starch for industrial
use oras pellets for animal feed (Office of Agricultural
Statistics,
1992).
In Thailand
cassava occupies the second largest area, only next to rice,among the crops. During the 1980s its acreage increased from 1.38 million ha in1983 to 1.62 million
ha in 1989 while the average yield varied between 12.7
ton/ha and 15.2 ton/ha.
The major cassava area is in the Northeast
regionamounting to 61 %of the total cassava planting area, followed by the Central Plainregion with 33 % and the North region with 6 %. However, during the recent
years (1989-1992)
total cassava planting area decreased by 8 % from 1.62 million
ha in 1989 to 1.49 million ha in 1992 (Office of Agricultural
Statistics,
1992).
Total cassava production
also decreased by 16 % from 24.3 million tons of freshroot to 20.4 million tons (Tablel).
The decrease was almost entirely due to adecrease in planted area. The minor fluctuations
from year to year are mainly
caused by price variations which in turn are due to the foreign market situation.
Although the planted area was considerably
decreased over these years, theThai cassava policy still aims at reducing the cassava planting by 160,000 ha in 5
years because the reduced cassava export price is imminent due to the anticipatedremoval of preferential
tariff treatment to cassava importationin EC. As thecassava acreage decreases the higher yielding
cultivar will be necessary to increasecassava productivity
which in turn will lead to the higher competitivenessofcassava productionsin international
market. To achieve this goal, broadening
genetic variability
through cassava collectionin the country, introduction
from
Table

1. Cassava plantedarea, production

and average yieldin Thailand

Y e ar

(P 0la0 n0 t ehda )P(0r0o 0d utc) tio n

Yft /hie ald)

19 8 319 8 419 8 519 8 61987
19 8 8
1989
1990
1991
1992

1 ,3 8 5
1 ,4 0 5
1 ,4 7 7
1 ,2 4 0
1 ,4 1 1
1 ,5 8 0
1 ,6 2 1
1 ,5 2 9
1 ,4 9 1
1 ,4 9 1

1 9 ,3 1 6
1 9 ,9 8 5
1 9 ,2 6 3
1 5 ,2 5 5
1 9 ,5 5 4
2 2 ,3 0 7
2 4 ,2 6 4
2 0 ,7 0 1
1 9 ,7 0 5
2 0 ,3 5 6

1 3 .9 5
1 4 .2 2
1 3 .0 4
1 2 .6 6
1 4 .2 6
1 4 .4 1
1 5 .2 3
1 3 .9 1
1 3 .7 4
1 4 .0 3

Source : Officeof Agricultural

Economics,

1992.

65

foreign countries and also recombinationof the desirable
would be important and challenging
task.

charactersamong them

Cassava Genetic Resources in Thailand
Germplasm collection
and introduction
The first step in any crop improvement program is the collectionof bothlocal and exotic germplasm and its evaluation.
This phase has received substantial
international
support and has resulted in two large cassava germplasm collections
at two international
research centers, CIAT and IITA. This was followed by thedetailed
plans for further collections,and continuing
attempts to standardize
theevaluation and disseminationof the results (Jennings and Martin 1973; Kawano etal 1978; Hahn et al 1979) CIAT 1980).
Both international
centers have been very
active in identificationof elite genotypes,
development of advanced breeding
materials
and distributionof improved populations
to the national
programs
throughout the world.
In Thailand
cassava breeding research began with the collectionof local
cultivars throughout the country and their systematic evaluationin 1956 at Rayong
Field Crops Research Center in Rayong province. There were not many cultivars
and several accessions, collected from various locations and having different names,
were identified
to be the same genotype. This was called "Local Rayong" to be
used in comparison with introduced cultivars.
Before 1960, some twenty cultivars had been introduced,
probably
fromMalaysia,Java and Mauritius.
From this stock, the venerable Local Rayong
probably emerged. During the 1960Ts, more clones were introduced, from Java in
1963, and from the Virgin Islands in 1965.
The first introductionof planting
material from CIAT took place in 1970 (Table 2). It appeared that Local Rayong
had higher yielding
capacity than any of the introduced
clones from Java, the Virgin
Islands
and CIAT then available.
This cultivar was named Rayong 1 by the
Department of Agriculture
in 1975 and constituted
the central pilar of the highly
Table

2. Introduction
Departmentof cassava germplasmof Agriculture.

Y e arN u min btro
erd ou fc ed
g e n o ty p e s

B efo re 1 9 6 0
19 63
19 65
19 70
19 7 7
1975‑ 1993

ab o u t 2 0
7 c u ltiv a rs
44 clo n e s
5 a cc ess io n s
10 h y b rid c lo n e s
13 0 ,3 87 see d s

Source : Field

Crops ResearchInstitute,to Thailand

through

O rig inM alay a , Ja v a , M au ritiu s, etc
J av aV irg in Islan d
C IA T
C IA T
C IA T

Departmentof Agriculture.

the

66

successful

Thai cassava production industry (Field Crop Research Institute,1992).
During the 1970s, we attempted to improve Rayong 1 by producing hybrids
using solely Thai germplasm; however, we could not select many recombinants
clearly superior to Rayong 1 in yield and adaptation.
Thus, introductionof exotic
germplasm became inevitable(Field Crops Research Institute,1992).
The introductionof CIAT germplasm in the form of hybrid seeds started
in 1975. Hybrid clones were first introducedin the form of meristem culture fromCIAT in 1979. Introductionof CIAT seed populations
from more specificallydefined cross parents, adapted to the Thai conditions,started in 1982 and continues
in the shape of annual introductionof 8000 to 10000 seeds from many crosses. All
these introductions
have passed and are passing through several evaluation steps ofthe breeding program and selected clones are utilized in hybridizations.
Germplasm introduced
from CIAT contributed
to increase the genetic
variability.
Many crosses were made every year between Thai and CIAT clones,
supplemented
by a smaller number of crosses between Thai clones. Recently, weplan to receive a duplicateof the core cassava collectionof the CIAT Worldcassava collection
at Rayong Research Center.
Preservationof genetic

materials

Since cassava is highly heterozygous,
vegetative propagationis required tomaintain genetic integrity.
Field maintenance is expensive and risk the loss ofgenotypes due to occasional years of environmental stress or heavy pathogen/pest
attacks. In response to these problems, Rayong Field Crops Research Center under
the Field Crops Research Institute,
Department of Agriculture,plans to develop aminimum growth germplasm conservation
system through the tissue culture
technique in addition
to the traditional
field conservation.
However, the cassava
research staff at this center still faced so many problems including fund and certain
facilities
to initiate this work. Many advantages such as lower cost of maintenancecompared with field maintenance and, the most importantly,
the avoidance of pestor pathogen contamination
as well as biotic and abiotic field pressures will give along term advantage to this method.
Cassava Breeding

ProgramCassava breeding including
hybridizationin Thailand
has been conducted at
Rayong Field Crops Research Center (RAY-FCRC), Field Crops Research Instituteof the Department of Agriculture,
and at Sriracha
Research Station (SRS)of
Kasetsart university since 1975 and 1983, respectively(Sinthuprama
and Thiraporn,1987).

67

The major objectivesof the cassava breeding

program are:

1. higher yielding
capacity
2. higher root dry matter content
3. early harvestability
4. good adaptation
to local production
environment with droughttolerance, etc.
5. disease and pest resistance
6. good plant type
7. good stake quality(handling,storage and germination)
8. root color
9. lower root cyanide content
Breeding high yielding
culivar is based on high yield, high harvest index,
and high root dry matter content.
The development of new cassava cultivars
involves the following
steps
annually (Sinthuprama
and Thiraporn,1989):
1. Hybridization
2. Seedlingselection
15,000-20,000
seedlings
3. Single-Row
trial:
1,500-2,000
clones
4. Preliminary
trial:
100-140 clones
5. Standard yield trial:
20-30 clones, 3 locations
6. Regional yield trial:
8-12 clones, 8 locations
7. On-farm trial
3-5 clones, many locations
8. On-farm test:
2-3 clones, many locations

Table

3. Recommended cassava cultivars

C u lti v a r s

r e Yle ea as re d

R ay o n g 1
R ay o n g 2
R ay o n g 3
R ay o n g 6 0
R ay o n g 9
S ri r a c h a 1
K a setsart 5 0‑
1984
19 8 319 8 719 9 119 9 1
1992

Source : Field

Crops Researchin Thailand

P a r e n ts

M a in fe a t u re s

S e l e c t e d f ro m l o c a l c u l tiv e r
M C o 1 1 13 x M C o1 2 2M M ex 5 5 x M v e n 3 0 7
M C o 1 16 8 4 x R ay o n g l
C M C 76 x V 43
(M C o 1 1 1 3 x M C o 1 2 2 ) x R ay o n g 1
R ay on g l x R ay on g 9 0

Institute,

Departmenty i e ld , p la n t ty p ee d ib le u s ero o t D M
e a r ly h a r v e s t , y ie ld
r o o t D M , y ie l dr o o t D M , p l a n t ty p e
r o o t D M , y ie l d p la n t ty p eof Agriculture.

68

Achievemen ts
Recommended Cultivars
The Department of Agriculture
has released five cultivars up to present(Table 4). Rayong 1 is basicallya farmers1 cultivar.
However, it was collected,
purified, evaluated, named and recommended by the Department of Agriculture.
It is a high yielding
cultivar with moderately
high harvest index. The cultivar
provides a good quantity of high quality planting
stakes and sprouts well evenunder water deficient conditions,which makes this cultivar highly
versatile.
Datafrom CIAT suggest that Rayong 1 is superior to most Latin American cultivars
under conditions
similar to those found in the Thai cassava area.
Rayong 2 was selected from the hybrid seeds introduced
from CIAT in
1975.
This cultivar
is especiallysuitablefor making fried chips and otherconvenient foods, and has a higher yielding
capacity than its counterpart Hanatee,
the traditional
table type cultivar.
Its yellow
root flesh contains high carotene.
Rayong 2 was released in 1985.
Rayong 3 was selected from hybrid seeds introduced from CIAT in 1975.
The results of experiment conducted from 1979 to 1984 show that the root dry
matter and starch content of Rayong 3 are higher than those of Rayong 1 while
fresh root yield is similar to that of Rayong 1. Higher starch content results in ahigher price being paid for roots of Rayong 3. The higher dry matter content ofRayong 3 is prefered by the chippers because it requires in a shorter time fordrying.
Rayong 3 was relesed in 1984.
Rayong 60 was selected from a cross produced at RAY-FCRC between
CIAT and Thai clones (MCol 1684 x Rayong 1). It has outyielded
Rayong 1 at
both early (6-8 month) and regular (12 month) harvests by 8% and 5% in freshroot, respectively,from a series of regional and on-farm trial during the period offour years (1984-1987).
It has also outyielded
Rayong 1 by 9% and 7%,
respectively,in root dry matter yield.
Hence, this cultivar can be used both forearly and for 12 month harvest. It was released by the Department of Agriculture
Table 4. Yield data of 5 cassava cultivars and a promisingfrom 53 on-farm trials and tests.
C ultiv ar

R ay o n g 1
R ay on g 3
R ay on g 6 0
R ay o n g 9 0
K a setsa rt 5 0
C M R 25 ‑105‑ 112

a promisingclone, averaged

R o o t y ie ld (t/h a )rf e shd ry

R oot D M
c o n)te n t(%

R o o t sta rc h
co n ten t

T o tal p lan t(t/hw e iga )h tH I

2 2 .3 9
1 9 .0 3
2 3 .5 8
2 3 .4 9
2 4 .8 3
2 5 .5 0

3 0 .6 8
3 4 .19
3 1 .5 2
3 4 .7 1
3 3 .9 8
3 3 .7 1

1 6 .7 2
2 1 .7 3
1 7 .6 7
2 2 .1 7
2 1 .2 2
2 0 .8 5

3 8 .6 0
3 0 .2 1
3 7 .4 3
3 7 .2 8
3 9 .4 1
3 9 .8 4

0 .5 8
0 .6 3
0 .6 3
0 .6 3
0 .6 3
0 .6 4clone selected

6 .9 3
6 .2 8
7 .4 08 .3 6
8 .5 1
8 .7 0from 27-77-10

x Rayong 3.

69

on September 30, 1987.
Rayong 90 was a hybrid production at RAY-FCRC of CMC 76 from CIAT
with V 43 from Virgin Island in 1978. Selection
and multi-location
trial wereconducted in the research centers and experiment stations of FieldCrops
Research
Institutesince 1983. From 159 trials conducted through 1984 to 1990, Rayong 90
has outyield by 5% in fresh root, and 1% in dry matter yield those of Rayong 1.
It has also outyield 18% in fresh root, 21% in starch yield and 20% in root dry
matter yield those of Rayong 3. Rayong 90 was released in 1991.
And Kasetsart University
has released two cultivars (Table 3):
Sriracha 1 is a selection from a cross made at Sriracha Research Station ofKasetsart University in 1983 between MKU 2-162, a selection from a CIAT hybrid
population,
and Rayong 1. The fresh root yield of this cultivar is similar to that ofRayong 1 whereas its root starch and dry matter contents are consistently
higherthan those of Rayong 1. The germination capacity, vegetative vigor and plant typeof Sriracha 1 are similar to those of Rayong 1 so that farmers can treat it exactly
in the same way as Rayong 1 but obtain higher starch yield.
Kasetsart 50 is a resultant of collaborative
research among researchers from3 institutes;
Kasetsart University,
Department of Agriculture
and CIAT. The
cultivar is a selection from the cross between Rayong 1 and Rayong 90 produced
in 1984. Kasetsart 50 possesses outstanding
germination,
fresh, dry and starch yield
and, consequently,
higher farmers' income. When compared with Rayong 1, KU
50 has 11% fresh root yield, 23% dry root yield higher than those of Rayong 1.
It was released in 1992. Promising new clones and future direction.
CMR25-105-112
is selected from the hybrid between 27-77-10, a local
selection from a cross made at CIAT by a thai breeder, and Rayong 3 performed
at RAY-FCRC in 1982. On-farm evaluation data indicate that this clone is afurther improvement over the previously
released cultivars (Table 4,5). The dataalso offer a good demonstrationof the step by step process of cassava varietal
improvement in yield characters (Table 4,5). Compared with Rayong 1, all the newcultivars
are characterized
by distinctly
higherharvest index (HI) while theTable

5. Yielddata of5 cassava cultivars

and a promising clone as relative to Rayong 1(average data from 53 trial in 1991-1992)

C u lti v a r

R o o t y i e ld
fr e s hd ry

R oot D M
c o n te n t

T o t a l p la n t
w e ig h t

H I

R ay o n g l
R ay o n g 3
R ay o n g 6 0
R ay o n g 9 0
K a s e t s a rt 5 0
C M R 2 5 ‑ 10 5 ‑ 1 1 2

100
85
105
105
111
114

100
91
107
121
123
126

o/
100
111
103
113
111
110

10 0
78
97
96
10 2
10 3

100
109
109
109
109
110

from 27-77-10

x Rayong 3.

* a promisingclone selected

70

improvement over Rayong 1 in other yield components were a gradual process andfurhter improvement in total biomass yield (TBY) seems to be much desired.
We suggested that a simultaneous
improvement in HI and TBY in thesegenotype
would give additional
adaptation
to both high and low yielding
environments (Kawano, 1990).
We also showed that further improvement in HI
and TBY were possible (Kawano et al, 1992). This promising clone CMR25-105112 with higher HI and biomass than Rayong 1 gave higher yield than Rayong 1
in both low and high yielding
enveronments throughout its on-farm evaluations.
It can grow and survive very well, still giving higher yielding
capacity underdrought environment or grown in late rainy season. Many more clones endowedwith these characters are coming out of the selection
pipelines.
These seem toindicate the directionof our breeding efforts.
In summary, further improvement of cassava yield and adaptationisimminent by selecting higher biomass and root DM content, while maintaining
high
HI.

Varietaldissemination

With the overwhelming success of Rayong 1, which coincidedwith themassive shift of Thai cassava production for human food to industrial
processing,virtually
all but one, Hanatee for snack cooking, traditional
cultivars
were wiped
out. Rayong 1 occupied more than 99% of the total national cassava acreage untila few years ago. Rayong 3 is now planted in 56,000 to 90,000 ha dependingon
the sources of estimate (Field Crop Research Institute,
1992; Chainuvat, et al 1993)
and the newest cultivars are rapidly catching up. Ironicallyhere in Thailand,theprocess of modern cultivar diffusion
is a process of partially
recovering the genetic
diversity
in production
field.

REFEREN CES
Chainuvat,

C, C. Boonmark and K. Klakhaeng. 1993. The cassava productionand extension
programe in Thailand.
Proc. IV Asian Cassava Research Workshop (Nov, 1993,
Trivandrum, India).
In press.
OAT, 1980. Centro Internacionalde Agriculture Tropical,
Cali, Colombia, Annual Report, 1980.
Field Crops Research Institute.
1992. Cassava Research Annual Reports 1976-1992.
Field
Crops Research Institute,
Department of Agriculture,
Bangkok, Thailand, (in Thai)
Hahn, S.K., E.R. Terry, K. Leuschner, I.O. Akobundu, C. Okoli and R. Lai. 1979. Cassava
Improvement in Africa. Field Crop Res. 2:193-226.
Jennings, D.L. and F.W.Martin. 1973. The utilizationof cassava variability
on an international
basis;
the report of study group. Paper presented
at 3 rd. Symp. Intern. Soc. Trop. Root Crops,
Ibadan, Nigeria.
Kawano, K. 1992. OAT cassava germplasm and its roles in cassava varietal improvement in Asia.
In: R.H. Howeler (Ed).
Cassava Breeding, Agronomy and Utilization
Research in Asia.

71

Proc 3rd. Regional Workshop, Malang, Indonesia.
Oct. 22-27, 1990. pp. 170-184.
Kawano, K., P. Daza, A. Amaya, M. Rios and W.M.Goncalres - Fukuda. 1978. Evaluationof cassava
germplasm for productivity.
Crop Sci. 18:377-380.
Kawano, K., S. Sarakarn. A. limsila, A. Tongglum, and D. Suparhan. 1990. Cassava cultivar
evolution viewed through harvest index and biomass production.
In: R.H. Howeler (Ed).
Proc. 8th Symp. Intern. Soc. Trop. Root Crops. Oct 30-Nov 5, 1988, Bangkok, Thailand.
pp. 202-211.
Office of Agricultural
Economics. 1992. Agricultural
Statisticsof Thailand,
Crop Year 1992. Officeof Agricultural
Economics, Ministry of Agriculture
and Co-operative,
Bangkok, Thailand.
Sinthuprama,
S. and C. Thiraporn. 1987. Cassava varietal improvement in Thailand.
In Cassava
Breeding:A
multidisciplinary
review, Proc. workshop held in Philippines,
4-7 March, 1985.
Clair H.Hershey (Ed). OAT, Cali, Colombia. 312 p.

73

Questionsand Answers Session 1

S.Sakaguchi(Q):species

What is the current
in cassava breeding.

situationand future plans for using wild

K.Kawano(A): CIAT has not been particularly
strong in completeing
the collectionof wild Manihot species. CIAT has so far not felt a strong need to look fordesirable
genes from wild relatives.
An old British cassava breeding
program in East Africa was successfully
incorporated
resistance to African
Mosaic disease from M.glaziori into commoncassava germplasm and IITA
inheritedthese materials and has used them in their breeding program.

M.Nakaghara(Q):You mentioned three methods of preserving cassava. In addition,
you mentioned seed preservation.
Could you comment further on seed
preservation.
K.Kawano(A):In addition to 1. field maintenance^,in vitro culture maintenanceand 3. cryopreservationof cassava germplasm at CIAT we are keeping alarge amount of sexual seeds coming mainly from open pollinationof many
clones. Keeping seeds is an additional
safty measure to the three methods
mentioned. Genotypes may be lost but most genes are kept by this method.

H. Takagi(Q):In the breeding objectivesof CIAT "versatility"
this mean "multipurpose
varieties"?.

is mentioned.

Does

K. Kawano(A):"Versatility"means dual purpose for processing
and fresh
consumption. Breeding is much simpler if it is only for processing.
Whendual purpose varieties are needed the cassava roots must have a low cyanide
content and favorable eating quality,that is usually difficult
to achieve.
However, we have selected and released Rayong 3 in Thailand and Malang
2 in Indonesia which are basicallyhigh starch content cultivars but can also
be consumed as fresh boiled cassava as well.

V.Ramantha Rao(Q):Were there differences
plantingfrom a single plant?

in volume density

in cuttings

forM.Oka(A):There is a large differencein volume density of cuttings
among
varieties.
Within the stakes of a variety, the volume density of lower parts

74

is higher except in the basal part of stakes. According to the results of ourexperiments,
cuttings
with high volume density of more than 1 cangerminate even under dry soil conditions.

I. Shiotani(Q):species.

Dr. Oka you mentioned the differencein germination
Is the differencein emergence of the root prominent?

among

M.Oka(A): Germination rate can be presented as the survival rate at about 30 days
after planting,since germinating
cuttings often die within 2 or 3 weeks after
planting.
It is a characteristics
of cassava germination that rooting is earlier
than shooting.
The shoots (sprouts)
which appear on the top part of stakes
without rooting cannot survive more than one month.
K. Takayanagi(Q):laborious
harvesting

How do you uproot big cassava roots?
It would seem very
to harvest by hand. Is there any breeding
objective
for easyof cassava roots?

C. Thiraporn(A):Currently, most cassava in Thailand is being harvested by hand.
We expect in the future to use machine harvesting.
Ease of harvest is avery important breeding objective.
Cylindricaluniform roots tend to givea high yield and are relatively
easy to harvest.
F.Kikuchi(Q):You mentioned root color as an important
would like to know the importance of this trait?

breeding

objective.

C.Thiraporn(A):Some starch factories give a lower price for yellow flesh cassava.
Cassava for snack chips requires yellow color flesh.
Generally
speaking
white colored flesh is preferred for diverse kinds of processing.

ITECHNICAL REPORTS

Session2

POTATO

Chairmen
Susumu Sakaguch
Jose L. Bacusmo

Management and Multiplicationof Potato in Japan

AKIO SUEMATSU1

Abstract
Unlike seed crops such as rice and wheat, tubers are used as seeds in potato cultivation.
The
tubers are vegetative
organs in which various diseases and pests tend to be retained and thesepathogens often spread out from tubers as the source of infection causing considerable
reduction in
the potato yield. It is important to establish
a seed potato multiplicationand certification
program torealize successful use of potato genetic resources.

In troduction

The Japanese climate differs greatly from region to region. This is largely
due to the country's length of 3,000 km. The north of Japan isin the sub-frigidzone and the south in the sub-tropicalzone. Potatoes are cultivatedcommerciallyall of the prefecturesin Japan.
There are several cropping types of potato
cultivationin Japan, and they can mainly be divided into three types including
spring, summer and autumn cropping types.
Potato Breeding Programs have been conducted at Hokkaido National
Agricultural
Experiment Station, Hokkaido Konsen Agricultural
Experiment Station
and Nagasaki Prefectural Agriculturaland Forestry Experiment Station.
More than
30 potato varieties which have excellent adaptations
and high qualities
have beenreleased. New potato varieties have also been introduced from foreign countries by
the Potato Breeding Programs or some private enterprises.
They differ in time of
maturity, yield, appearance, cooking and marketing qualities,
and resistancetovarious diseases and their use for potato cultivation
depends on the regions.
The leading
potato varieties
in Japan in order of popularity
areDanshakuimo, May Queen, Benimaru, Noring No.l and Dejima.
Danshakuimo is one of the most famous potato variety in Japan, and isplantedthroughout
Japan because of its wide adaptation.
This variety was
introduced in 1905 from America, and its original name in America is Irish Cobbler
which is believed to be a bud mutation of Early Rose. Danshakuimo has earlymaturing habit, and round tuber shape. The tuber has deep eyes, white flesh colorand long dormant period. May Queen is a potato variety introduced from Britain
in 1917.This
variety has excellent cooking quality, and has medium maturing habit

National Center for Seeds and Seedlings
Tsukuba, Ibaraki 305, Japan

78and shallow eyes. The tuber is long to oblong in shape,and pale yellow in flesh
color.
Benimaru which was released in 1938 has elliptic,
pale red tuber andshallow eyes and is a potato variety used mainly for starch production.
Norin No.l
is a potato variety released
in 1943.
It has a wide adaptability
for several
consumption purposes includingtable use, starch production
and processing for
potato chips. This variety has some resistance to brown rot and Fusarium dry rot.
Dejima is a potato variety that has a high adaptability
for the potato
cultivationin double cropping region due to an extremely short dormance period.
This variety was released in 1971, and became to be a main potato variety indouble cropping regions.
About 120,000 ha of the potatoes are grown in Japan, and as much as
250,000 ton of seed potatoes are needed by commercial potato growers. The seedpotatoes can be divided into three categories namely - foundation seed, registered
seed and certified
seed potatoes.
The foundation
seed potatoes are produced anddistributedby the National
Center for Seeds and Seedlingsof MinistryofAgriculture,
Forestry and Fisheries.
They are planted and the tubers are harvested
to produce the registered
seed potatoes.
The registered
seed potatoes are planted
the following
year to produce certified seed potatoes which are used for commercial
potato cultivation.
In 1989 production of foundation,
registeredand certified
seed
potatoes was 1,900, 23,000 and 183,000 tons respectively.

Productionof foundation

seed potato

Unlike seed crops such as rice and wheat, tubers are used as seeds in the
potato cultivation.
The tubers are vegetative organs in which various diseases andpests tend to be retained and tubers act as a source of infection for these pathogens
which can cause considerable
loss of yield.
Pathogens, particularly,
viruses andpotato ring rot are latent in tubers, and can not be controlled
by chemicals.
Therefore,
a continuous supply of the healthy,
disease free, seed potatoes isnecessary. The multiplication
rate of the potato is low compared to other crops andthe cost of seeds and seedlings to the total production
cost is relatively
high forpotato production.
Therefore, it becomes extremely important to establish
a seedpotato multiplication
organization
to supply healthy seed potatoes at low prices, andsystemic distributionof seed potatoes for commercial potato cultivation
is essential
to improve potato production.
It was with these points in mind that, the Japanese government establishedseven Potato Foundation Stock Seeds Farms in northern parts of Japan in 1947, andan additional
Foundation Stock Seeds Farm was establishedin southern Japan in
1960. These Potato Foundation Stock Seed Farms were reorganized as stations of
the National Center for Seeds and Seedlingsin 1986.
All foundation
seed potatoes of current and new varieties are produced in79

stationsof the National Center for Seeds and Seedlings.
The propagationoffoundation seed potatoes at the National Center forSeeds and Seedlings first begins
with virus free tubers prepared by the meristem culture technique.
The first reportof successful productionof a virus-free potato plant from an infected plant bymeristem culture was from research conducted by Yora and Tsuchizaki(1962).
Soon after this success, the techniqueof meristem culture was introduced
toproduce the virus-free foundation seed potatoes.
The first virus-free foundation
seed potatoes of potato varieties were obtained at a station of the National Center
for Seeds and Seedlingsin 1967. Since that time, meristem culture has been used
to eradicate potato viruses from almost all potato varieties planted in Japan.
To produce foundation seed potatoes, virus-free potato tubers prepared bymeristem culture are planted in a screenhouse to produce pre-basic seed potatoes.
The pre-basic seed potatoes are planted in basic seed potato fields the following
year to produce basic seed potatoes. Finally,
the basic seed potatoes are used to
produce the foundation seed potatoes.
The pre-basic seed potatoes of some potato varieties are propagated by invitro rapid multiplication
technique.
After virus-free potato plants are produced bymeristem culture, they are multipliedby means of in vitro mass tuberization.
There
are two main steps in the in vitro mass tuberization
process, the first process is invitro layeringof plantlets
derived from meristem culture on the surface of a
medium to multiply the number of shoots. The second process involvesthe transfer
of axillary shoots to a medium containing high concentrationof sucrose to produce
micro-tubers in vitro. These micro-tubers are propagatedin the screenhouse to
produce the pre-basic seed potatoes.
At the National Center for Seeds and Seedlings,
various inspection
tests
including electron microscopy, serologicaltests, sap inoculation tests, tuber indexing
tests and roguing are performed at each of the propagation
stages to ensure highquality seed potatoes. Electron microscopy is used to inspect plantlets
derived fromtissue culture, and pre-basic seed potato plants. Serologicaltests are very usefulfor large-scale testing, and antisera that have a high titer against the main potato
viruses and bacterial
diseases are produced in the National Center for Seeds andSeedlings
and used for the serologicaltestings.
ELISA is the most sensitive
serologicalmethod that is commonly used to detect potato virus infection at the
National Center for Seeds and Seedlings.
For the inoculation
tests, Chenopodium
quinoa, Physalis floridana, Gomphrena globosa and many Nicotiana species areused. Although the reactions of the test plants to potato viruses are often not
specific,the inoculation
test is very sensitive compared with commonserologicaltests for the detection of potato viruses.
It is very important to remove diseased plants as soon as possible during
production of the foundation seed potatoes to prevent the spread of virus diseases
from virus infected potato plants to healthy ones. Most of the potato varieties
planted in Japan react to virus infections with clear symptoms such as mosaic, vein
clearing, leaf rolling or necrosis depending on the potato virus and potato variety

80

combinations.
Therefore,
symptomatology
is a very importantelement inrecognizing
virus infected potato plants in the field.
At the National Center for
Seeds and Seedlings,
roguing of diseased plants is carried out more than 10 times
during the seed potato growing period until the haulm of the seed potato plants has
been destructed
artificially.
Infections
early in the growing season result in
symptoms being expressed in the leaves. These potato plants are removed by theroguing after symptom expression.
However, later infection
sometimes does not
result in any symptoms in the haulm, although the developing
tubers of the plant
many already be infected.
Therefore, tuber indexing is performed for post-harvest
control of virus infectionof the basic seed potatoes,
and to predict the virus
infection of the foundation seed potatoes. In tuber indexing, one eye of tuber is cut
from potato tuber to be tested. The eyes cut from tubers are planted in greenhouse,
and resulting young plants can be inspected 4-5 weeks latter, depending on potato
varieties
and on growing conditions,by visual inspection,
inoculation
tests or
ELISA.

Productionof registeredand certified

seed potatoes

Productionof registered
seed potatoes and certified
seed potatoes
areimportant steps in the seed potato multiplication
system to maintain the quality of
seed potato. The production of registered
seed potatoes is, in principle,
operatedby the local government. However, in many cases, it is entrusted to seed potato
growers who are proficientin techniques such as detection of virus infected plants
and virus disease protectionneeded in seed potato fields.
The productionofcertified
seed potatoes is run by individual
seed potato growers. There are about
5,600 seed potato growers in Japan, and they belong to regional
Seed Potato
Growers Co-operative Association.
The fields and places used for seed potato
production
are usually locatedwithinthe same locality
but isolated
fromcommercial potato fields.
The seed growers have to pass field and harvest inspections
conducted by
Plant Quarantine Officers to sell and transfer their products as seed potato.
This
seed potato certification
program was initiatedin 1951.
Application
inspection
forms are sent from individual
seed growers before the planting season of the seedpotatoes requestinga listing of varieties,classificationand source of seed lots, area,
field number and location, previous crop history of fields and date of planting.
This
information is used by the Plant Quarantine Officer to determine eligibility
for theinspections.
The field and harvest inspections
are carried out on the incidence of 9
potato diseases and pests. In the field inspection,
if more than 0.1 percent virus
infected potato plants are found during the final field inspection,
the seed field is
no longer entitled to be the registeredor certified seed field. Special emphasis isplaced on the occurrence of bacterial ring rot and potato cyst nematode. Bacterial
ring rot and potato cyst nematode are so contagious that they have a zero tolerance

81

at any stage throughout
the growing season of seed potatoes.
The harvest
inspection
is conducted especiallyon the presence or absence of powdery scab,
commonscab, potato tuber moth and potato cyst nematode. As failure to meet thetolerance is cause for rejection, lack of isolationof the seed potato fields, unsuitablecultural conditions
and high aphid population
are also cause for the rejection.
Atthe beginningof the seed potato certification
program, the rejection
rate of seedpotatoes was more than 25 percent due to a high incidence of viruses and unsuitablecultural conditions.
However, the recent rejection rate of the seed potatoes is lessthan 1 percent. This certification
program of the seed potatoes has been conductedin ll prefectures which are the main potato producing areas in Japan.
Conclusion
When vegetatively
propagated plants like potato are infected with a disease,the pathogen passes from one generation to the next. The entire populationsof avariety are infected with the same pathogen, and the yield and quality of the variety
gradually
decreases over time. In order to ensure the successful use of potato
genetic resources, establishmentof a propagation and certification
system for seedpotatoes is needed.
Techniques such as meristem tissue culture, rapid in vitro
multiplicationand virus testing are very important.
References
Clark,

MRand Adams, AN. 1977. Characteristicsof the microplate
method of enzyme-linked
immunosorbent assay for the detectionof plant viruses. Jour. Gen. Viol. 34:475-483.
Horio, H. 1972. Productionof virus-free potatoes by means of meristem culture. Research Bulletinof the National Potato Foundation
Stock Seed Farm. No.6, 1-19. (in Japanese).
Horio, H. 1976. Studies on M-mosaic and S-mosaic of potato. Research Bulletinof the National
Potato Foundation
Stock Seed Farm. No.12, 1-94. (in Japanese).
Kojima, M.,Chou, T. G. and Shikata, E. 1978. Rapid diagnosisof potato leafroll
virus by immune
electron microscopy. Ann. Phytopath.
Soc. Japan. 44:585-590.
Kojima, M.,Takizawa, T.,Uyeda, I. and Shikata, E. 1982. Applicationof enzyme-linked
immunosorbent assay to diagnosisof potato leafroll
disease. Ann. Phytopath.
Soc. Japan.
48:458-465.
Kojima, M.,Uyeda, I.,Aoki, T. and Shikata, E. 1980. Detectionof potato leafroll
virus in the potato
leaves and sprouts by ELISA. Ann. Phytopath.
Soc. Japan. 46:274-277.
Mori, K,Hayama, F.,Shimomura, T. and Ikegami, Y. 1969. Productionof virus-free plants by meansof meristem culture. J. Gen. Agr. Expt. Sta. No.13, 45-110. (in Japanese).
National Center for Seeds and Seedlings.
1991. Experimentson necrotic strain of potato virus Y(PVY) in potato cultivars and its control. Research Bulletin of the National Center for Seeds
and Seedlings.
No.2, 1-64. (in Japanese).
National Center for Seeds and Seedlings.
1993. Study on method of multiplicationof potato throughmicro-tubers
produced in vitro. Research Bulletinof the National
Center for Seeds andSeedlings.
No.3, 1-109. (in Japanese).
Tanaka, T. 1974. Studies on the potato leaf-rolldiseases. Research Bulletin of the National
PotatoFoundation Stock Seed Farm. No.10, 1-116. (in Japanese).

82

Tanaka, T. 1980. Experiments on resistance to potato virus X, A and Y on potato varieties.
Research
Bulletinof the National Potato Foundation
Stock Seed Farm. No.14, 1-49. (in Japanese).
Uyeda, I.,Kojima, M.,Yomenura, M.,Aoki, T. and Kawada, T. 1984. Applicationof enzyme-linked
immunosorbent assay to a large scale indexing of potato virus X, Potato virus Y, and potato
leafrollvirus. J. Fac. Agr. Hokkaido Univ. 62:22-35.
Weidemann, H.L. 1988. Importance and control of potato virus YN (PVY N) in seed potato
production.
Potato Research. 31:85-94.
Yora, K. and Tsuchizaki,
T. 1962. The eliminationof latent viruses from potatoes of Danshaku variety
by use of tissue culture. Ann. Phytopath.
Soc. Japan. 27:219-221.

Characterization,
MOTOYUKI

Evaluationand Use of Potato

in Japan.

MORI1

Potatoes (Solarium tuberosum L.) were introduced to Japan at the beginningof 17th century, but its cultivation
did not spread until the end of the 19th century,
during the Meiji era. The area of cultivation
increased rapidly
because potatoes
were used as a processing material for starch in the 1900s. As potato is a crop
suitablefor cool climates,
Hokkaido is the main producer of potato9)'u).
1991
statistics
show that Hokkaido
accounted for about 75% of the total production(3,609,200t)
and 60% of the total cultivatedarea (lll,840ha)of potatoes
inJapan1^
From the end of the 19th century to the beginningof the 20th century, anumber of American and European varieties
were introduced
and repeatedly
evaluated.
After 1902, a national potato breeding
program was started to test
varieties
and select lines. As a result many introduced
varieties
were selected asrecommended varieties.
Old introduced
varieties
such as "Danshakuimo" (Irish
Cobbler)and "May Queen" still remains leading varieties
for culinary use. In 1916,
artificial
hybridization
was initiated,
continuous effort have been made, and a lotof varieties
for starch production were bred, such as "Benimaru" and "Norin No.l",these still remain leading varieties.
Inter-specifichybridization
started in 1939.
South American landraces
and wild species (S. demissum, S. chacoence, S.
stoloniferum,etc.) were used as high starch, pest and disease (late bright, Y-virus,
cyst-nematode etc.) resistant genes donor. "Konafubuki" is resistantto the Y-virus
and "Toyoakari" is resistantto the cyst-nematode,
both contain more than 20%
starch. In food processing,"Toyoshiro" remains a leading variety was first bred for
potato chips, and "Hokkaikogane"
was released for frozen fried potatoes9)>11) (Tablei).

Evaluationof potato germplasm started as a national
project
in 1985.
Although botanical features and agriculturalcharacteristics
used in this project arevery useful for general use in breeding,
it is necessary to evaluate the genetic
characteristics
for breeding. Potato breeding objective
has changed from the yieldconsiderations(productivity,
pest and disease resistance etc.) to quality,
because ofchanging consumer's needs. The desired qualitiesof potato are as follows:9)>12)

1 Hokkaido

National

Shimo-shimamatsu,

Agricultural

ExperimentEniwa, Hokkaido

061-13,

Station,
Japan

84

Table

1. Outline*Firstof potato

introduction

introduction

and improvementin Japanto Japan*Many varieties were introduced from North America
including:
Early Roser Snow Flake. Green Mountain,
American Wonder. Early Beauty of HebronT etc.
*Breedingprogram was started(1902)*Artificial
crossing was initiated(1918)
Irish Cobbler (used as basic breeding material),
May Queen)s*Many varieties were introduced from Europe
Pepo (male parent of Benimaru),
Deodara (male parent of Norin No.l))s*First hybrid varieties
were released (1938)
Benimaru, Myojo, Hokkai-shiro*Many and wild relatives
were introduced*Inter-specifichybridization
was started (1939))s

Norin No.l (1943)*Establishment
of Seed Foundation

Stock Farms (1947))s""Introductionof new American varieties by G.H.Q. (1954)
including:Kennehecr Wheeler, etc.
Hochprozentige(1956from Germany, high starch gene donor)
Yoraku (1958, derived from inter-specifichybrid)Unzen and Tachibana (1955, for double cropping))s

Rishiri (1960, aneuploid,
late blight
Yukijiro(1961,
for mashed potato),
Bihoro (1969, high starch 25%))s

Dejima(1971,
for double cropping),
Waseshiro(1974),
Toyoshiro(1976,
for chips)
Tunika(l 978T from Germany, cyst-nematode resistance)
Nishiyutaka(1988, for double cropping))s

Konafubuki(1981),
Toyo-akari(1986),)s

Touya and Musamaru (1992),
Hokkai No.73, Koniku No.26 and Saikai
under line:

introduced

resistance)

Hokkaikogane(1981,
Kita-akari(1987)

variety.

for fried potatoes)

No.23 (1994)

85a) Post harvest characteristics;
good tuber shape, shallow eye depth, tolerance tomechanical damage, greening tolerance, long dormancy, etc.
b) Processing
adaptability;
high starch content and good starch quality,
low
reducing sugar content under low temperature storage, no browning after peeling,
no blacking after cooking, etc.
c) Cooking quality;
good flavor, taste, texture, skin and flesh color, high vitamin
C and low glycoalkaloids
content, etc..
Some of the quality characteristics
have been incorporated
into breeding lines,
and new varieties. For example, "Kita-akari"
has high vitamin C content and good
taste, "Touya" has good round shape tuber and low discolorationin the raw andcooked state, "Hokkai No.76" has very low reducing sugar content suitable forchips.
Breeding

for specifictraits:(a) Low reducing sugars content3)>5)
The variety used for potato chips must have low reducing sugar content. Highlevels of reducing sugars leads to discoloration.
A low level of reducing sugars bothat the harvest, during long storage and during reconditioning
is important.
Most
cultivars
accumulate significant
amounts of reducing
sugars when stored attemperatures below 7°C.
Genetic stock lines were selected for direct chipping without reconditioning
under low storage temperatures.
MND860-2" (the North Dakota State University
breeding clone with 5. phureja in its background)and some lines of S. tuberosumssp. andigena (Andigena)
were selected,
and crossed with common potatoes(Tuberosum)
to transfer cold chipping
abilityi.e. the potato does not accumulate
reducing sugars during low temperature storage and will produce acceptablycoloredchips with little reconditioning.
In 1987, a search began to select parents which were capable of coldchipping.
After some preliminary
tests, 81 strains of old and new commonpotato
varieties
and lines, lines of Andigena and their hybrids
were induced in a final
evaluation.
After tubers had been harvested, they were allowed to cure for one
month, then were stored at 8°C for 107 days and 5°C for 137 days. Then they wereimmediately
made into chips in the standard way. In evaluation, the Agtron readingof 25 or over is commerciallyacceptable
for making chips. Andigena and the
hybrid group showed more genetic diversity
than the commonpotato group (Figurei).

Many crosses were made with good materials selected from this test,
subsequent selectionof progeny families continued. The tubers of selected
lines
were stored at 6°C for 5 months. They were directly chipped and evaluated. Alsosugar content was examined. "Hokkai No.76" and "Shimakei No.561" are progenyof "ND860-2", and "WB86013-17"
is progeny of "Andigena(234)M,
these lines

86

FigureTable

1. Evaluationof lines with chips
storage temperaturecolor under different

2.

of varieties

Cold chipping
qualitycharacteristics
for 5 months at 6°C

1) Agtron model 500 (small angle viewer)
at 0 and 90.
2) Sugar analyzer YSI model 27.

possess

excellentchipping

quality(Tablewith green filter

storedstandardized

2).

(b) Low discoloration6*
12)
Recently there has been an increasing
consumption of pre-pealedor cutpotatoes. These products are mainly consumed in fast-food restaurants, and sold in
take-out food shops or supermarkets. Because of browning after peeling decreases
the value of potato products, low discoloration
is an important trait for commercial
cooking.

87

There are big varietal
differencesin browning after peeling. Newly bredvarieties
belong to the low discolorationgroup, while Irish Cobbler, a leading
variety for culinary use, belongs to the worst group (Figure 2). "Hokkaikogane"issuitable for packaged slicing or cutting, due to its very weak discolorationin theraw and cooked stage, and firmness on cooking. Also Kita-akari
which is a very
mealy cooking type of potato with a high solids content and weak discolorationiswell suited for producing mashed potato salad.
(c) Greening
tolerance and glycoalkaloid
content2)>4) 12)
Absence of tuber greening is important for marketing. Potato skins change
to green when exposed to light and green skins have a bitter taste.
Tubers of 421 genetic stocks and breeding lines were exposed to sunlight for
two weeks in the field during September 1992, and much variation for greening wasobserved (Table 3). Red or purple skin varieties
did not become green, but theirflesh become green in the same way as other varieties.
There is a correlation
between skin and flesh greening, but there is no relationshipbetween greening andglycoalkaloid
biosynthesisin the potato tubers.
Fortunately,a new breeding line, "Hokkai No.74", has both tolerance togreening and low glycoalkaloid
biosynthesis.

Browning degree
Figure 2.

Browning after peeling(cutting)

in potatovarieties

88

Table

3. Relationshipbetween skin and flesh of tuber greening
varieties for two weeks under sunlight(r=0.643***)

Note: White

Figure3.

and brown skinned

varieties

in potatowere tested.

VitaminC content(mg / lOOg FW)

VitaminC content of tubers in progeny

families(d) Vitamin
C content4* 10)
Vitamin C content of selected parent varietiesand progeny families wereanalyzed. Only L-ascorbic acid in the tuber was analysed by the high performanceliquid chromatography(HPLC) method because dehydroascorbic
acid is in verysmall quantities.
Sample tubers were harvested on September 2nd 1992, andanalyzed on middle of September. From preliminary
tests it is known that all parent
varieties (23.6-29.8
mg/lOOgFW)
belong to the group with high content of vitamin

89

C. Only one progeny family was significantly
different
from other tester. Someclones, which contained 44.0 mg/lOOgFW, surpassed the vitamin C levels of theirparents, but did not have twice the vitamin C content of parents. 44.0 mg/lOOgFWis the same level as that of "Kita-akari"a variety with the highest vitamin C level(Figure 3). It is presumed therefor, that breedingfor high vitamin C content wasreached its upper limit.

(e) Phosphorus
content in starch9) 10)
Potato starch is used in many food products. When water is added, uponheating, potato starch gelatinizes
at relatively
low temperatures, and shows a highviscosity,
which is closely connected with Phosphorus content. These characteristics
are suitable for traditional
foods manufacture such as fish meal sausage, boiled or
baked fish paste "Kamaboko" or "Chikuwa", and Japanese noodle "Udon".
Phosphorus content in starch of parent varietiesand progeny families wereanalyzed. Sample tubers were harvested on September 24th 1992.
A significant
difference(l%)
between two progeny families was found during
evaluation.
Cross number 90101 aimed to breed for low phosphorus
content.
Among the progeny families (with a mean of 580ppm),
the lowest phosphorus
content clone was 387ppm. Cross number 90098 aimed to breed for highphosphorus
content, among the progeny families (with a mean of 980ppm)
one
clone had a phosphorus content of 1201ppm. 387ppm and 1201ppm are probably
the limits of phosphorus
content in potato starch (Figure 4).

Phosphorus

Figure 4.

Phosphorus

contents(ppm)

content of tubers

in progeny

families

90(f) Anthocyanin
pigments4)'7) 8)
Solanum phureja(?huie]a)ydihaploidof Tuberosum and Andigena have beenused to breed red fleshed potato. Anthocyanin
pigment content in tubers wasevaluated using the extinction
coefficient of extracted juice color. The pigment
content increased quickly within two generations,the pigment content increased one
hundred times (Figure 5).
Tetraploid
species of the Andigena group which has partly pigmented flesh
was used in breeding. Within two to three generations,deep pigmented flesh lines(red and blue) were selected (Figure 6).
Diploid lines were superior than tetraploidlines with respect to concentrationof pigments. But tetraploidlines have more acceptable yield and agronomic traits.
In the near future, the potatoes with red and purple flesh color will be not
only used in table varieties,
but also used in food processing,for instance toproduce colored potato chips and mashed potato powder. If anthocyanin
pigments
are more concentrated
in fresh, the natural edible pigments
can be reasonably
collected
from residues of potato starch industry.

Phureja(114)x us-wl
Phureja(276)x W624209-H.10(2x Tuberosum)(2x Tuberosum)

2x Andigena(217-H.2)

x W822229-5[0.01]

W6522195-21
x P10173-5(2x from CIP)

[0.01]

W862207- 1

x

W872209-5[0.08][0.10]

WB902241-12[0.94]

Figure 5. Pedigree of red fresh diploid
potato[ ]: indicate
the density of pigment (Extinction
coefficient).

Norin No.l x Andigena(553-4)(Tub ero sum).
Irish Cobbler x Andigena(553-4)(Tub ero sum)
KW85093 -33[0.13]

80135-21
x R392-50(Tub ero sum)x

86083 -78
[0.03]

90107-2[0.70]

Figure 6. Pedigree of red flesh tetraploid
potato[ ]: indicate
the density of pigment (Extinction
coefficient).

91

References
1) Hokkaido
Kyodokumiai
Tsushinsha(1993):
Agriculturein Hokkaido.
Hokkaido
Kyodokumiai
News-agency, Sapporo, Japan, 13.
2) Kimura,T., M.Mori and Y.Umemura (1992):
Varietaldifferencein potato tuber greening. Rep.
Hokkaido Branch Crop Sci. Soc. Jpn. & Jpn. Soc. Breed., 33, 40-41 [In Japanese].
3) Mori,M. and S.Nishibe(1989):
Evaluationof potato chip color of Solanum clones at different
storage temperatures.
Rep. Hokkaido Branch Crop Sci. Soc. Jpn. & Jpn. Soc. Breed., 29, 30[In Japanese].
4) Mori,M., T.Maida G.Ishii
and Y.Umemura (1991):
Some chemical characteristics
in potato
breeding- ascorbic acid, anthocyanin
and glycoalkaloids-. In Asian Potato Association
Proceedings,
Bandung Indonesia,
31-35.
5) Mori,M., T.Kita, S.Nishibeand Y.Umemura (1991):
Breeding for low reducing sugar clones under
low temperature
for potato chips. In Abst. 79th Conf. Jpn. Soc. Breed.,266-267[In
Japanese].
6) Mori,M., T.Maida and Y.Umemura (1991):
Discolorationof raw potato tuber. 1.Relationshipofdarkening with variety, tuber size and specificgravity. Rep. Hokkaido Branch Crop Sci. Soc.
Jpn. & Jpn. Soc. Breed., 32, 30-31 [In Japanese].
7) Mori,M., T.Maida, Y.Umemura, N.Kusano and T.Sumita (1992):
Breeding for high anthocyanin
potatoes. (1) The increase of pigments content in diploidhybrid progeny. In Abst. 81th Conf.
Jpn. Soc. Breed., 354-355[In Japanese].
8) Mori,M., Y.Umemura, N.Kusano and T.Sumita (1992):
Breeding
for high anthocyanin
potatoes.
(2) The increase of pigments content in tetraploidhybrid progeny. In Abst. 82th Conf. Jpn.
Soc. Breed., 482-483 [In Japanese].
9) Mori,M. and Y.Umemura (1992):
Current situationof potato processingin Japan. JARQ Vol.26,
No.3, 157-164.
10) Mori,M., K.Yamamoto, T.Kimura and G.Ishii (1993):
Potato breedingfor chemical components.
l.Phosphorus
content in starch and vitamin C content. Rep. Hokkaido Branch Crop Sci. Soc.
Jpn. & Jpn. Soc. Breed., 34, 112-113[In Japanese].
ll) Nagata,T. and N.Takase (1967):
Hokkaido nogyo gijutu kenkyu shi (The historyof agricultural
technology
and research in Hokkaido).
Hokkaido Nat. Agr. Exp. Sta., 223-243 [In Japanese].
12) Umemura,Y. (1993):
Evaluationof potato germplasm introduced
from Russia. Japan-Russia
Workshop Gen. Res. Biotech., 105-108.

In vitro Preservationof Potato

Genetic

Resources in NIARTERUO ISfflGE1

Abstract
In vitro preservation
technologyof annual vegetative crops, such as potatoes {Solarium
tuberosum), has solved the problems associated with field preservationsuch as high labor costs. This
technology
can also prevent the deteriorationof quality due to diseases. We are conducting a project
for establishinga long-term preservation method for potatoes. We have developed a media in which
potatoessurvive for one year or more without subculturing.
In the case of potatoes, we can makemicrotubers in the test tube. These microtubers have many applications
for usage of genetic resources
and in cell biology.

Potatolines

storedin vitro

Genetic resources stored in vitro at the Laboratory of Plant Cell Breeding(LPCB) are listed (Table 1). P lines are collectedfrom Potato Breeding Stations
and Center for Seeds and Seedlings,
MAFF. Ag lines are potato lines transformed
by Agrobacterium tumefaciens. F lines are somatic hybrid possessing cell selection
markers transformed by A tumefaciens. I lines are somatic hybrids
withouttransformed markers. Due to regulation
regarding transformed plants, we can notplant Ag lines and F lines in the field. We should keep these materials in closed
conditionsat present.
PathogenElimination

Meristem culture was the first biotechnologicalapproach successfully
adopted and applied to obtain virus-free potato stocks. This method is being
applied in combination with thermotherapy
and chemotherapy to obtain virus-freestocks for further propagation
as well as for the production of clean seeds which areplanted over large areas. Thismethod of using disease-freestocks has resulted in an increased yield in many
countries. Most potato lines stored in vitro at LPBC are virus-free stocks.

National Institute
Tsukuba, Ibarakiof Agrobiological305, Japan

Resources

94

Table

1. Potatolines stored

L in ein vitro at Laboratory

N o . o f a c c e s s io n s

P (a re n ta l) l in e s
S . tu h e r o s u m
S . tu b e r o s u m
w il d s p e c i e s
S . a c a u leS . b r ev id e n s
S . n ig r u m
S . p h o t e in o c a rp u m
S . b u lb o c a s ta n u m
S . p e r u v ia n u m
S . p i n n a tis e c tu m
S . v er ru co s um
S . m o r e ll if o r m e
S . e tu b e r o s u m
S . m u r ic a t u m
S . c h a co en se
S . m e g is ta c r o lo b u m
S . p h u r ej a
S . c a r d io p h llu m
A g i r o b a c te r iu mt r a n s f o r m e d ) lin e s
F (u s e d w ith
m a r k e rs ) l in e s
I ( o a ) lin e s

G enom eof Plant

Cell Breeding
T u b e ri z a t io n

3 2 4 (to t a l)
242
45

4x
2x

13
6
3
2
2
2
1
1
1
1
1
1
1
1
1
1 0 2 4 ( to ta l)

2x
2x
3x
2x
2x
2x
2x
2x
2x
2x
2x
2x
2x
2x
2x
2 x ,3 x ,4 x

Y es
N o
N o
N o
Y es
N o
N o
N o
Y es
Y es
Y es
N o
Y es
Y es
Y es
Y e s, N o

1 2 0 ( to ta l)

4 x ,6 x ,8 x

Y es

H O ( to ta l)

4 x ,6 x ,8 x

Y es

Y es
Y es

Micro- propagation
Potatoes are conventionallypropagated through tubers. Using totipotencyof cells, in vitro technology has been applied to produce plantlets
on a large scale.
Three
in
vitro
approaches
aregenerally
appliedforpotatopropagation/multiplication:(1) culture of nodes; (2) microtuber
formation; and (3)somaclones and gametoclones through callus or protoplast.
Meristem derived virus-free plants are cut into small segments with nodes( including
a leaf and an axillary bud ), and cultured. The rate of growth andmultiplication
is faster in liquid media compared to agar medium.
The in vitro productionof microtubers is another approach which can beappliedto the potato seed industry
and storage of genetic resources.
The
microtubers weigh between 10-40 mg each and have two or more eyes. They havethe advantage over test-tube plants in that they can be produced in large numbers
irrespectiveof the season, can be easily stored, packed and shipped with less injury.
In vitro conservation
To maintainof genetic

resources

potato clones, the germplasm is traditionallyconserved through95

tubers, which have to be grown and multiplied
every year. This method is not only
time consuming, labour-intensive
and expensive, but, above all, the material is
exposed to hostile environments and the hazards of pests and pathogens which may
result in the total loss of the germplasm. This problem has encouraged attempts todevelop in vitro methods of conservation.
On normal growth medium, in vitro plants have to be transferred frequently
to fresh medium, a transfer process that is very labour-intensive.
Therefore,
methods to reduce the growth rate have been studied. Growth limitation
could beobtained by adding inhibitors,
reducing the energy source, lowering the incubation
temperature or applying osmotic stress.
Weare conducting a project to establish
a long-term preservation method
for potatoes. As a result of these studies and experiments, the following facts haveso far been observed. For potatoes, 39 lines of 13 species and 6 somatic hybrids
survived for one year or more without subculture at 20°C on Rl medium mainly
consistingof MS medium containing 0.5% sucrose and 4% mannitol.
Considerable
difference
was observed in the survival and health among
different lines. When cultured in the medium for long-term preservation,
abnormalplants were observed in a number of the lines used. This problem remains to besolved for the preservationof vegetatively
propagated crops.
Transportof genetic

resources

Potatoes germplasm preserved in vitro have applications:among them arein vitro application
as a material of tissue culture, direct cultivationin the field anddistribution
to users. There is the need to develop preservation
methods suited tothese various uses, taking into account the cost involved. In the case of potatoes,
we can make microtubers in the test tube. Microtubers
have certain advantages
over the test-tube
plants for storage and exchange; they can withstandlongerperiods in the dark, and also changes in outside temperature better. They can beeasily transported
in small bottle to various destinations,stored, planted
andmultiplied.
For successful
in vitro propagationand distribution,
the plantlets
transferredfrom the test tube to the soil require
specialcare. For example,
adaptation
to low humidity is critical,
especiallysince the roots that have developedin vitro are often not very efficientin the soil. Potato tubers produced in vitro adapt
easily to low humidity
when transferredto the soil. The in vitro storage andexchange of germplasm ensures the supply of virus-free materials, and it reduces
the chances of disseminationof other diseases which normally occur through theconventional
method of exchange by tubers.
Application

polyploidy,

to cell biology
Somaclonalvariation,
may be due to such factors as endomitosis,
aneuploidy,
gene amplification,
somatic crossing-over,transposable

96

elements,
sisterchromatid
exchange,or crypticchanges associatedwithchromosomal rearrangement. The potato appears prone to such variation.
Wedeveloped 4,000 lines regenerated from discs and protoplasts,
and made microtuberof these lines. These microtubers were planted in the field
and tested their field
performance at the Potato Breeding Station in Hokkaido Agricultural
Experiment
Station.
Extensive
phenotypicvariationin potatoplantsregenerated
from
protoplasts,
and tuber discs were observed. The plants showed differencesin height,
size, dormancy and yield of tubers. The inductionof genetic variability
and theselection of desirable somaclonal variants would increase the pool of germplasm foruse in potato breeding
program. This would facilitate
the early release of newcommercial varieties.
Somatic hybridization
through the fusion of protoplasts
is now a more orless routine techniquein many crops. In potato a number of reports are available
on the somatic protoplast
fusion. This could be a powerful tool for the induction ofgenetic variability
in this corp. We are conducting a project to fuse protoplasts
between diploid potato lines. Somatic hybrids which showed hybrid vigor have beenobtained.
Microtuber from these somatic hybrids were planted in the field and tested
for agronomic characters.
Genetic

Stability

Genetic variation due to chromosomal rearrangements can occur in tissue
culture. A correlation exits between the time plant material is grown as callus andthe probability
for chromosomal change. The use of axillary buds as a base formultiplication
reduces the chance of genetic variation.
The best method for long term conservationof potatoes
will becryopreservationin liquid nitrogen, but this methods is not yet applicablefor a large
collection.

Referen ces
R. Aida, F. Takaiwa, T. Imai and T. Ishige. (1991)
Analysisof distribution
and diversityof patatin
promoters in Solanum species by using the polymerase chain reaction technique
Japan.J.Breed.,
41:511-515
T. Imai, R. Aida and T. Ishige. (1993)
High frequencyof tetraploidy
in Agrobacterium-mediatedtransformants regenerated
from tuber discs of diploid potato lines. Plant Cell Reports,
12:299-302
T. Imai, Y. Irikura and T. Ishige. (1992)
Studies of the gene expression in a somatic hybrid of
dihaploid
Solanum tuberosum and diploid S. brevidens using two-dimensional
proteinelectrophoresis.
Plant Cell, Tissue and Organ Culture, 29:115-124
T. Ishige, M. Ohshima and Y. Ohashi. (1991)
Transformationof Japanese potato cultivars with the
B-glucuronidase
gene fused with the promoter of the pathogenesis-related
la protein geneof tobacco. Plant Science, 73:67-174

97

D. P. Rajapakse,
T. Imai and T. Ishige.
dodecylsulfate
polyacrylamide(1991)
Analysisof potato microtuber
gel electrophoresis.
Potato Research,

proteins by sodium
34:285-293

99

Questionsand Answers Session 2

S.Sakaguchi(Q):eliminateis good.
applicable?

To exchange genetic resources internationallyquarantine toviruses is necessary.
An easy and accurate test such as ELISA
Are there any viruses for which the ELISA method is not

A.Suematsu(A):I think that provided one can obtain antibodies,
one can use the
ELISA method for any virus. At least for potatoes the ELISA test can beused for any virus. However, the concentrationof virus affects the test.
When the concentrationof the virus in the plant is low, they cannot be
detected.
With this in mind the growth of the plant and timing of the test
is crucial.

M.Nakagahra(Q):The National Center for Seeds and Seedlings(NCSS)
are
preserving many kinds of crop species as well as potatoes.
I'd like to know
the activities
concerned with germplasm conservation for your organisation.
A.Suematsu(A):NCSS is preserving foundation seeds of sugarcane and stock seedsof tea trees but not potato foundation seed. NCSS has four other mainfunctions:
1) DUS testing for the registrationof new plant varieties.
2) Quality testing of marketed seeds.
3) Research on seed technology.
4) Multiplicationand conservation of plant genetic resources of vegetatively
propagated crops.
Shiotani(Q):What species and at what ploidy level, did you use to produce thesomatic hybrids mentioned in your presentation?
If the parents weretetraploidthe somatic hybrids would be octaploidand sterility
would be a
problem.

T.Ishige(A):We used diploid parents for somatic cell fusion, so the hybrid is
tetraploid.
In this experiment,
our target is to get somatic hybrids whichshow high heterosis and are tetraploid.

S.Sakaguchi(Q):What problems

occur when exchanging

in vitro genetic

resources?

100

T. Ishige(A):Technicallyin vitro materials,
non-contaminatedthe adaptationof in vitro plants
we need reasonable quarantine
materials.

to soil is important.
For
rules, because these are

S.M.Z.Hasan(Q):You mentioned that no genetic change occurred in your potato
tissue culture storage system. How did you confirm this?
T. Ishige(A):Micro-tube culture is very stable, because we don't use any plant
hormones. We have a project to confirm the somoclonal change by RFLP
analysis.

H. Fujimaki(Q):Among various characteristics
of wild species what traits
think is the most promising for improving Japanese potato cultivars
fusion or another means of biotechnology?

do youby cellT. Ishige(A):Wild species have many good traits, such as resistance to diseases.
Wecan introduce these traits by cell fusion however undesirable
traits are
introduced too. We have to develop an asymetrical cell fusion system toovercome this problem.

V. Ramanatha Rao(Q): What are the safeguards
plants into the field?

taken for the releaseof transgenic

T. Ishige(A):Japan operates a step-wise procedure. We cannot plant transgenic
materials directlyin the field. First there is a security check in closed
conditions.
Then we can transfer transgenic plants to semi-open conditions.
Finally, we test the transgenic plants in the field. After going through thisprocess we can cultivate transgenic plants in the field.

K.Kawano(Q):Does cell fusion and somatic mutation, which occurs during in vitro
handling, still offer a bright promise in practical breeding? I am asking thisquestion because at a recent Cassava Biotechnology
forum, thesetechnologies
were not considered top priority.
T.Ishige(A):Somaclonal variation can be used directly in plant breeding.
Somatic
hybrids between haploids show hybrid vigor. We need joint projects
between plant breeders and tissue culture specialists
to realize useful resultsfrom these methods.

TECHNICAL

Session 3
SWEETPOTATO

Chairmen
Fumio Kikuchi
Truong van Ho

REPORTSSweetpotato
J.L.BACUSMO,

Genetic
V.Z.ACEDO,

Resources in the Philippines
A.M.MARISCAL

and M.Z.ORAQON1

Sweetpotato is an introduced
crop in the Philippines.
Although no record
exist, it is believedthat sweetpotato
was first introduced
into the Philippines
sometime in the 16th century through the "Galleons" that ply the Acapulco Manila route. It is not known how diverse the ancestral plants were but certainly
genotypic
variability
has tremendously
increased since introduction
through generecombination
by sexual reproduction,
mutationand varietal
introduction.
Spontaneous germinationof true seeds and human selection
must be largely
responsible
for the enormous genotypicvariabilityof sweetpotato
present in thePhilippines.
Today sweetpotato is an important food crop in the Philippines.
Each year
more than 130,000
hectares are planted to sweetpotato(Table 1). Per capita
consumption of sweetpotato ranged from 10.0 to 24.0 kg. Ninety five percent ofsweetpotato are consumed as food. The remaining 5% goes to feed and waste.
As sweetpotato is grown all over the country, farmers in different
regions
perpetuate varieties that are preferred in their particular
locality.
Preference to avariety is conditioned
by adaptability
to local conditions,eating quality and market
demand.
Loss of some important varieties
do occur usually after drought and asconsequence of introductionof more superior varieties.

Table 1. Area planted, volume of production
and average yield
sweetpotato
in the Philippines,
1986-90Y ear

A r(eha a )P l a n te d

1986
1987
1988
1989
1990

1 6 4 ,3 0 0
1 6 4 ,7 7 0
1 4 4 ,1 4 0
1 3 8 ,3 2 2
1 3 6 ,6 8 5

P roV d ou luc tio
m en o(Mf T )1 Professor, Asst. Professor, Assoc.Professor,
Training Center, and Associate Professor,
Botany, ViSCA, Baybay, Leyte 6521-A,

7 7 7 ,0 7 8
8 0 0 ,6 1 4
8 4 3 ,6 7 4
6 6 0 ,2 8 0
6 6 8 ,8 7 3of

A v(eMr aTg /he aY) ie ld

4 .7
4 .9
5 .1
3 .1 94 .6 6

Philippine
Root Crop Research andDepartment of Plant Breeding and Ag.
Philippines.

104

Germplasm Collected
Nationwide collectionof sweetpotato
germplasm started in 1976 as part of the"Program for the Establishmentof a National Root Crop Research and Outreach for
the Philippines"
which was supported by the International
Development ResearchCentre (IDRC)
of Canada and the then Philippine
Council for Agricultural
Resources Research (PCARR).
Under this program, collection
trips to the different
regions of the country were undertaken to establish
a sweetpotato
germplasm
collection
at the Philippine
Root Crop Research and Training Center (PRCRTC)
atthe Visayas State College of Agriculture(ViSCA),
Baybay, Leyte. Germplasm
from other countries were also obtained
through correspondence
and personal
contact. The number of accessions of /. batatas and /. trifida x /. batatas hybridsin the collection
is shown (Table 2).
Aside from PRCRTC, other government agencies such as Universityof thePhilippinesat Los Banos (UPLB), Department of Agriculture(DA) and Northern
Philippine
root Crop Research and Training
Center (NPRCRTC),
CentroInternationalde la Papa Philippine
Regional Office (CIP) and international
projects
such as Southeast
Asian Program for Potato Researchand Development(SAPPRAD),also maintain sweetpotato collections
for their breeding work. To
minimize duplicationof efforts, collecting
in Luzon area is assigned to NPRCRTCand UPLB, while Visayas and Mindanao is assigned to PRCRTC.
Maintenance
Field Maintenance
At PRCRTC, sweetpotato accessions are maintained in one
meter quadrats in the field genebank.
In each quadrat, 12 cuttings are planted.
Table

2. Number of accessions of/, batatas and /. trifida x /. batatas hybridsin the PRCRTC, UPLB and NPRCRTC germplasm collection
N o of A c ces sio n ss o u rce s

I. b a ta ta s
P h ilip p in e s
T aiw a n (A V R D C )U .S .A .
C h in a
N ig eria
P a p u a N e w G u in ea
Ja p an
In d on esia
A n onym ous/. trifi d a x /. ba ta ta sFl
B Cl
T ota lPRC RTC

U PL BN PR C RT C

800

653

800

653

1059
80
47
25
25
17
15
15
14

19
1324

105

MonthsFigureAdjacent
annually
spraying

1. Planting and replanting
at PRCRTC

cycle of sweetpotato

germplasm

accessions are separated bby one-meter alleys.
Replanting
is donein the same plots as shown in Fig. 1. Fertilizer
applicationand chemical
are kept at the minimum.
At UPLB, sweetpotato
accessions
are maintainedin pots, while theDepartment of Agriculture
and Northern Philippine
Root Crop Research andTraining Center grow their collectionsin 4-6 meter rows.
In vitro Maintenanceof Sweetpotato
Germplasm
Backup collectionof selected
cultivars are kept in vitro as the field genebank is exposed to biotic and abiotic
risks. PRCRTC establisheda small tissue culture laboratory for this purpose. Using
nodal segments of VSP1 to 6, culture medium formulations
consistingof theMurashige and Skoog basic nutrients supplemented with 3% sucrose and different
levels of mannitol and sorbitol were studied.
The osmotic regulators were used tominimize growth and to prolong tissue maintenance without subculturing.
Results have shown that mannitol at 2% was able to reduce the growth ofplantlets
compared to the control. However, greater growth reduction was observed
at 4% level. Root growth was inhibitedor reduces and resulted to the formationof smaller leaves and closer internodes.
Plantlets
exhibitinga miniature habit.
When sorbitol was used, however, a comparable growth rate with the control
occured at 2% and growth reduction was only observed at 4%.
Increasing further the levels of mannitol and sorbitol to 8% did not favor
desirable growth of tissues. A cauliflower type of growth with callus formation wasobserved in most of the cultures.

106

Cultures on 2-4% mannitol and 4% sorhitol were maintained for about ayear. When the miniature plantlets
were transferred directly to the regeneration
medium or the normal growth medium, the roots grew fast and the growing leaves
became bigger and the internodes
longer.
When the plantlets
were subcultured
using nodal segments and inoculated
into the normal growth medium, they
produced normal plantlets with no discernible
differences from the control plantlets.
At present, 9 selected sweetpotato cultivars, 64 accessions from CIP and 82
embryo cultured hybrids of /. trifida x /. batatas are maintained in tissue culture.
There are plans to conserve Philippine
sweetpotato
germplasm in vitro but atpresent the Philippine
govrnment is not capable to support long term activities
ofthis sort.
In situ Conservation
Efforts to promote community based genebanking
in thePhilippines
has been spearheaded
by UPWARD (Users Perspective
with
Agricultural
Research and Development).
The project is still on it's infancy stage
and strategies
to convince farmers to initiate
and sustain community-based
genebanks is not yet defined.
Characterizationand Evaluation
Descriptionof the accessions is complete for above-ground parts using the
CIP descriptors
list for sweetpotato (except for floral characters).
Data are stored
in the computer for easy retrieval.
Evaluation of the germplasm collection of PRCRTC since 1976 has focused
predominantly
on yield. Accessions were evaluated in preliminary
and replicatedyield trials.
About 20% of the collection
had been evaluated in replicatedtrials.
From these 20% , some high yielding
accessions were identified
which were usedin subsequent breeding works. Other popular farmer varieties
such as "Miracle"and "Karinkit" were also utilized
as parents. Recently, 50% of the collectionwasevaluated for yield.
Results show that about 75% of the collection
gave yields
ranging from 1-10 tons/hectare.
Some cultivars however gave yields of 156 - 25
tons/hectare(Fig. 2). The variationin skin and flesh color in the collection
isshown (Figs. 3 and 4). About 40% of the collection
have red skin and about 30%
have yellow flesh. Both of these characters
are preferredin the market forsweetpotato.
Screening for non-sweet varieties,
tolerance
to acidic soils andtolerance to shade were also done (Tables 3 & 4).
Germplasm Exchange
Within the Philippines,
agencies freely exchange sweetpotato germplasm.
With agencies outside the country, only "pathogen tested" germplasm materials are
accepted.
However due to weak quarantine regulations/facilities,"non pathogen
tested" germplasm can slip through.
Exchange of botanicalseeds is virtuallyunrestricted.
Philippines
is willing to exchange materials as long as reciprocity
isobserved.

107

Figure2. Yieldlevelsof SP germplasm

collection

Figure 3. Skin color of sweetpotato(w/o fertilizer)

germplasm

108

FigureTable 3.

4.

Flesh color distributionof sweetpotato

Yield (ton/ha),weight of herbage (kg/pit)of the 10 selected sweetpotato
genotypes
Matalom, Leyte Philippines
1989

germplasm

and percent survival
in single row trial,

109

Table

4.

Total yield of sweetpotato
accessions
under shade, VISCA, 1990

A ce . N o(k Yg /pield
l o t)

PRS
V SP
PRS
PRS
PRS
I

419
7
ll1
45 6
396

1 3 .2 4
9 .6 2
5 .9 7
4 .1 6
3 .9 7
1

PRS
PRS
PRS
PRS
PR S

526
243
238
285
180

0 .1 60 .15
0 .15
0 .0 50 .0 5Figure5.

Project

structure

Germplasm Use
At PRCRTC, organized breeding effort on sweetpotato started in the late
70fs. Interdisciplinary
breeding program was later implemented with the supportof International
Development Research Center (IDRC)(Fig. 5). The breeding110

program largely
use the polycrossmethod to generating
genotypic
variations.
Briefly, the polycross method as adopted by PRCRTC/ViSCA
can be outlined as:
1. Selectionof desirable
parents
2. Setting up of trellises
and planting of parents in mounds
3. Training the sweetpotato
in trellises.
4. Collectionof open pollinatedseeds
5. Germinating
the seeds in seed beds
6. Planting
terminal cuttings from seedlings followed bystrong selection.
Testing of genotypes generated from polycross nurseries and biparental
crosses in several locations
across the country was also started in the 80Ts.
Promising
genotypes from UPLB and DA were also tested under this scheme
Observational^Preliminary

Trial
Trial

>U
General Trial(replicated,orie location)
Regional/Multilocation

FigureEvaluation

phasesTable 5. Recommended sweetpotato

varieties

V a ri ety

B NA 51
V SP 1V SP 2V SP 3
V SP 4
V SP 5
V SP 6
U P L Sp 1U P L Sp3U P L Sp 5
B PI Sp 1
B PI Sp2V SP 7
R ed W o n d e r
P SB Sp 15
P SB Sp 16
P SB Sp 17

6.

Trial

A v(MeragT /He Ya)ie ld

1 5 .22 0 .91 8 .71 7 .3
1 5 .71 7 .2
1 9 .5
1 6 .71 7 .7
1 3 .7
1 8 .5
1 7 .01 6 .4 6
1 4 .01 3 .8 3
12 .16
1 7 .0 9of the Philippines

D ry M atterS kin C olo r

F lesh C o lo r‑
2 6 .6
3 3 .33 5 .43 4 .03 4 .7
3 0 .6
3 7 .03 9 .03 0 .02 6 .03 1 .0‑3 0 .3 2
3 6 .3 0
3 7 .4 9
3 0 .12W h iteR ed
P in kR ed
W h iteP in kR ed
R ed
W h iteW h iteL ig h t O ren g e
W h iteO ran g e
R ed
C re amW h iteR ed

O ra n g e
O ran g e
O ran g e
Y ellow
Y ellow O ran g e
Y ellow P u rp le
W h iteW h iteW h iteW h iteO ran g e
L ig h t Y e llo w
O ran g e
L ig h t Y e llo o w
L ig h t Y e llo w
W h iteY ellowIll(Figure6).
To date 17 varieties have been recommended by the Philippine(Table 5). These varieties are recommended with yield across testing
matter and eating/processing
qualities
as the main criteria.

Seed Board
locations,dry

Screening for Resistance to Weevil and Scab
Since 1986 screening for weevil
and scab resistance have been going on. A total of 2,152 genotypes were evaluatedstarting from observational
trial.
Under field condition,
60 genotypes were rated
as moderately resistantor resistant.
When screened however using force feedingin pots and in close containers,
all genotypes
eventuallyexhibitedsusceptible
reactions (Fig. 7). The results suggest that only low level of resistance are available
from the germplasm. This low level of resistancehowever, may be useful whenused in combination with other control measures.
Using Ipomoea Relatives
for Sweetpotato
Germplasm Enhancement
Studieson Ipomoea relatives with the ultimate view to their possible
use in sweetpotato
breeding was started in early to mid-80fs.
However, the actual wide crosses wereachieved only in 1988. The Ipomoea relatives used included local and introduced
species from various sources. All these Ipomoea forms were field grown and only
the flowering and vigorous accessions were used in the subsequent crosses under

Figure7.

Reactions of genotypes
procedures

to weevil under different

screening

112

natural conditions.
The initial reciprocal
cross-compatibility
and crossability
tests
indicatedthat some cultivars set seeds when used as female in crosses with /. pescaprae, 2x /. trifida and 6x /. trifida while only the 2x, 4x and 6x /. trifida strains
set seeds when used as females in crosses with some cultivars.
However, all the
diploid
Ipomoea species and the /. trifida "species complex" showed evidence ofpollen tube growth in stigmas of some cultivars or vice versa, but failed to set
seeds. The sporad types and pollen stainabilityof these Ipomoea forms werestudied to asses their male/pollen
fertility.
Although sweetpotato has successfully
been crossed with /. pes-caprae andthe 2x, 4x and 6x /. trifida strains, the main focus of the wide hybridizationdone
so far was between hexaploid sweetpotato cultivars and the hexaploid /. trifida as
the initial step in broadening the genetic base of cultivatedsweetpotato
germplasm
using wild relatives.
Strains of /. trifida (6x) from Japan were used in thousandsof hand pollinations.
A higher seed set was obtained when sweetpotato was usedas female, but seed germination was about the same (40%) with seed produced withsweetpotato used as male or female. The Flfs have been tested and selections weremade based on root number, root weight, root diameter and high dry matter content.
Cytologicalbehavior of some Fl hybrids during meiosis indicateda highdegree of bivalent
as well as quadrivalentand hexavalent chromosome pairingassociations,an indicationthat chromosomes from the sweetpotato and the 6x L.
trifida strains were highly homologous.
The pairing behaviors
suggest thatrecombination
or exchange of genes could take place between these closely related
species to broaden the sweetpotato gene pool.
Backcrossingof the Fl's to selected
sweetpotato
cultivars
was done
resultingto 838 seeds from 104 cross combinations.
Percentage germinationof
BC1 seeds was 30.55% and 40% of these genotypes were selected after field trials
for further tests. Field evaluation of the BCl's from /. trifida x /. batatas, showsthat yielding
ability can be reconstituted
after a single backcrossing.
Table 6 shows
the yield and reactions to scab and weevil of the BCl's.
Though initial results(field screening)
indicates
resistant reactions to scab and weevil, it is too early toconclude that useful genes for resistance to weevil and scab were obtained fromcrossing /. batatas with /. trifida.
Adoptionof New Varieties
For the recommended varieties,
their adoption
is both slow and nonsymmetrical.
In some areas like Bicol, VSPs (ViSCA Sweetpotato)
are more
widely grown compared to areas such as Leyte and Samar which are closer to
PRCRTC.
Among the factors that contributeto this slow adoption of the new varieties
are the following.
1.

Shortcomingsof the new varieties
such as in eating quality,
storability
and adaptability
to marginal environment.
To increase

113

Table

6. Number of tubers, yield/. trifida x /. batatas

EN T R Y# o f tu b er/h ill

V S P l x 13‑ 1 P I
V S P l x 13‑ 1 P3
V S P l x 12‑3
V S P l x 24‑5 PI
V S P 2 x 12‑2
V SP 3 x 12‑2 PI
V SP 3 x 13‑ 1
V SP 3 x 13‑ 1 PI
V SP 3 x 13‑ 1 PlO
V SP 3 x 13‑ 1 P4
V SP 3 x 13‑ 1 P2
V SP 3 x 13‑2
V SP 4 x 13‑ 1 P I
V SP 4 x 12‑3 P2
V SP 4 x 13‑ 1 P3
V SP 4 x 13‑ 1 P2
B in o tatic x 1 3 ‑ 1 P I
M ira cle x 13 ‑ 1 P I
V S P 2 (Suscep tib le C h eck)V 3 7 ‑ 1 5 1 (Y ield C heck)2 .0
1 .2 00 .7 5
3 .1 00 .7 50 .2 5
1 .4 0
1 .0 90 .6 7
1 .6 7
0 .8 60 .2 55 .0
0 .8 31.0
1 .3 30 .7 5
0 .8 7
1 .0
1 .9 3and reactions

to scab & weevil of BC1

Y ield (k g /h ill)

S ca b (rx n )0 .1 20 .0 60 .0 1
0 .3 60 .0 50 .0 2
0 .2 60 .2 20 .0 20 .0 50 .0 30 .0 1
0 .2 50 .0 90 .0 30 .0 60 .1 00 .0 50 .2 90 .5 5

H R
H R
M R
H R
H R
H R
H R
H R
H R
H R
H R
H R
H R
H R
H R
H R
H R
H R
H R

W ee v il (rx n )

H R

M S
M R

chance of adoption, efforts are directed to involving farmers in theselectionof potential
varieties.
This somehow allows farmer
criteria
to be inputedin the selectionof potential
varieties.
PSBSpl5(Philippine
Seed Board Sweetpotato15), for example isa product of selection involving farmers from the preliminary
trial.
2.

Limited access of farmers to planting
materials of new varieties.
Unlike cereals the Philippine
government has no program on
distributionof sweetpotato
cuttings.
Moreover distributionofsweetpotato seedpieces
is difficult
due to : (1) high perishability;(2) bulk; and (3) difficulties
in maintaining/multiplying
quality
seedpieces
in the field.

3.

Stagnant
market of sweetpotato.
With nonexpanding
farmers find no incentive to adopt high yielding
varieties
to increase production.

market,in orderNevertheless,some newvarieties have started replacing traditionalvarieties
in semi-commercial
sweetpotato
growing areas. For subsistence
farms, it isextremely difficult
to assess adoption of new varieties due to the inaccessibilityofsweetpotato growers and loss of identityof new varieties from the usual practiceof naming/renaming
variety according to source.

114

Conclusion
The sweetpotato in the Philippines
exhibits wide genotypic variability.
It is
not known however, how wide the gene variability
is. Government agencies aswell as international
programs are presently
involvedin the conservation
andbreeding efforts on sweetpotato in the Philippines.
High yielding
varietiesofsweetpotato
were released by the Philippine
Seedboard.
Most of these weredeveloped through polycross breeding.
Using the wild relative /. trifida has also
been attempted.
Adoption of new varieties released by the Philippine
Seedboard
remains slow inspite of high yield and other superior traits of new varieties.
The present germplasm collection
has yet to be systematicallyevaluated forimportant traits in order exploit its full potentials.
Problems of continuing
andimproving present conservation
activities
on sweetpotato remains in view ofdiminishingfunds for research.

Sweetpotato

Genetic

Resources and Breedingin Japan

KATSUMI KOMAKI1

Sweetpotato
can convert solar energy to carbohydrates
efficiently
andtolerates
environmental
extremes, such as drought and typhoons, which causesignificant
losses to upland crop production.
Sweetpotato is thought to have been
first introduced
into Japan in the 1600s. By the middle of the 19th century it had
spread throughout Japan, except Hokkaido.(Kobayashi,
1984a) It is one of Japan's
most important upland crops, especiallyin southwestern Japan.
Between five and seven million tons of sweetpotato
were produced on
350,000 to 450,000 ha annually between 1945 and 1960. However the acreage andproduction
has been decreasing gradually
since then due to the higher price ofdomestic sweetpotato starch over imported corn starch and changes in Japanese diet.
Sweetpotato
production in 1992 was approximately
1.2 million tons on 55,000 ha.
About 30% is used for starch production,
30% is consumed as a fresh vegetable,
and the rest is used as animal feed, farmers' food and material for fermentation
products including
alcohol and alcoholic beverages.
Domestic sweetpotato starch has been protected for the last 20 years by apolicy related to the importationof corn starch.
The general tendency toward
global free trade of agricultural
products may remove protection for sweetpotatoes
produced for the starch industry.
This could result in a further decrease insweetpotato
production
and a decline in upland farming in southwesternJapan,
where sweetpotato is an indispensable
crop because of low soil fertility,
irregular
summerrainfall and frequent typhoons.
In such a situation,
new demands for sweetpotato
have to be developed.
Consequently,
diverse sweetpotato
germplasm is considered
important
for thedevelopment of new sweetpotato products.
The present paper reviews the current status of introduction,conservation,
evaluation and use of sweetpotato genetic resources in Japan.
Introduction

genetic

of genetic

resources

Since the first introductionof sweetpotato
into Japan a number of exotic
resources have been introducedby the National
Agriculture
Research

National

Agriculture

Tsukuba,

IbarakiResearch
305, Japan

Center,116

Center(NARC).
The origin of these introductionsin NARC is shown(Table
1).
Initially
many accessions were introduced from U.S.A., Taiwan, Philippines
andIndonesia.
Since the MAFF Gene Bank Project started in 1986, exploration
andcollection
has been conducted in Malaysia, Indonesia and Papua New Gunea forsweetpotato.
Introductions
include not only cultivars but also wild relatives.
In
1956 Nishiyama(1971)
explored Mexico and collected a number of wild relativesof sweetpotato including K123 which is a hexaploid
type ofIpomoea trifida.
K221
was collected in Mexico in 1960. This accession was originallycalled /. leucantha,
but now it should be identified
as a diploid
type of /. trifida.
In addition
Kobayashi(1984b),
Shiotani(1983),
and others collectedmany accessionsofsweetpotato,
including /. trifida. Species and accessions introduced since 1956 areshown(Table
2).
Introductions
coming into Japan must pass through the Plant Protection
Office of MAFF. Sweetpotato roots and foliage with a yellow tag issued by Plant
Protection
Office may enter Japan.
The yellow tag is a special permission
tointroduce
plant materials which are basicallyprohibitedto import into Japan byTable

1 Origin of introductions

conserved in NARC

Country

NumberCountry

U .S .A .

24

Philippines

B razil4

T aiw anM exico1

V enezuela

P apua N ew G uinea

37

C hin aM alaysia

58

O thers

Indonesia

43

U nkn ow n

Table 2

Wild species

Species

closely

relatedto sweet potato

Accessions

Ip o m o e a tr ifi d a (2 x )Number18

introduced

into Japan

Remarks

7 9 1 5 , 8 0 4 2 , e tc .

(3 x )

K 222(4 x )

K 3 0 0 , K 5 0 0 , 7 9 4 8 , e tc .

(6 x )K 123, K 177

F e r a l ty p e o f / , b a ta ta s !

/ . le u c a n th aK 2 21/. tr ifi d a (2 x ) 1/ . 1i t o r a l is

K 2 3 3 , etc

E c o t y p e o f /. tr ifi d a (4 x ) 1/ . tr i lo b a

K 1 2 1 , etc/ . tr i c h o c a rp a

7 9 3 4 , etc .

/ . til ia c e a

K 27 0/ . g r a c ilis

K 13 4/ . ti lia c e a l

117

Plant Protection Law. The germplasm issued yellow tag must inspected for virus
diseases and some kind of insects by Plant Protection
Office. If it does not pass
the inspection,
it is isolated
in the isolation
facilities
for upland crops in NARC
and shoot tip culture is performed. Virus free plants from shoot tip culture can beplanted in the open field after approval from the Plant Protection Office.
Genetic

resource

conservation

The accessions conserved in NARC consist of cultivars registered by MAFF,
breedinglines, local cultivars,
introductions
and hte collectionsof professor
Douglas Yen(Table
3). Genetic resources of sweetpotao are also conserved in
Kyushu National Agricultural
Experiment Station(KNAES),
the National Center for
Seeds
and Seedlings(NCSS),
and National
Instituteof Agrobiological
Resources(NIAR)
as shown(Table 4). Approximately
3,500 accessions, including
introductions
from many countries and breeding lines in Japan, are conserved.
Roots are usually stored in storage facilities
with a 13 C and 95% RH. However,plants of accessions that produce no storage roots are kept in the greenhouse above
15 C even in winter.
Species closely related to sweetpotato
are principally
Table 3 Sweetpotato

Table

4 Number of genetic

genetic

resources

resourcesin NARCof sweetpotato

in Japan(1993)

118

conserved as true seeds, but tetraploidand hexaploid types of /. trifida which cantolerate growing in pots all year are maintained this way. Since Yen's collection
have accessions which do not produce storage roots, hybrid seeds with somecultivars are also conserved in the Gene Bank Facilities
of NIAR.
Genetic

resources

evaluation

Genetic resources are evaluatedfor a range of traits which includes
morphologicaland physiologicalcharacters, tolerance and resistance to biotic andabiotic stresses, and yield and its component(Table5). In total, 50 morphologicaland 25 biologicaldescriptors
are used for registrationof new cultivars, and 30-40
characteristics
are evaluatedin the organizations
responsible
to sweetpotato
conservation annuall.
Use of sweetpotato

genetic

resources

1. Sweetpotato
cultivars
Genetic resources should be used for breeding from different
standpoints
ina crop improvement program.
Insect and disease resistance,
tolerancetoenvironmental extremes, nutritional
aspects are usually important traits for breeding.
Heterosis is expected from crosses between native cultivars or their progenies andexotic genetic resources.
For instance, high yielding
cultivars
are sometimes
developed by using exotic genetic resources, when genetic variation among native
breeding materials is limited.
'Koganesengan^Sakai
et al. 1967), a leading cultivar
for starch productionin Japan is related to T No. 3f and L-4-5, which wereintroduced
form Indonesia
and U.S.A., respectively.
Cultivars which have beendeveloped using exotic genetic resources are shown(Table
6).

Table

5 Evaluationof sweetpotato

rity
iry

genetic

resources

Characteristics
Plant type, Twining, Natural flowering, Vine pigmentation,
Matureleaf shape, Immature leaf color, Abaxial leaf vein pigmentation,
Leaf nectary color, Storage root shape, Storage root color, Storage
root flesh color, etc.
Selfand cross-incompatibility
Storability,
Stem rot resistance,root-lesion
nematode resistance,
Fresh root:Storage
content, etc.
Steamed root:Taste,group,
Sproutingability,
Soil rot resistance,
Root-knot andetc.

root yield,

Dry matter content,brix(%),

blackening,etc.

Starch

119

Table

6

Examplesof cultivars

developed

by using

genetic

resources(Origin)exoticgenetic

resources
Cultivars
developed

ExoticKoganesengan

L-4-5(U.S.A.),

T No. 3(Indonesia)

Minamiyutaka

K123(Mexico),

L-4-5, T No. 3

Benihayato

Centennial(U.S.A.),

K123

Caromex(U.S.A.),

Nancy Hall(U.S.A.),

HealthyRed

Tinian(Mexico),

L-4-5

2. Wild

relatives
Wild relatives are used for specific important traits, such as insect and disease
resistance,
and for widening
thegenetic
backgroundof cultivated
germplasm(Iwanaga,
1987).
The wild species that has been used in Japan's
breeding
program is /. trifida which can cross with sweetpotato
irrespective
polyploidy.
K123 reported by Nishiyama as a hexaploid
type of /. trifida wasextensively
used in breeding
for increased starch production.
Althoughthetaxonomic identityof K123 has been questioned(Jones,1967),
I call it /. trifida inthis paper. Hybrids between sweetpotato and K123 were backcrossed to improved
cultivars.
From BC2 progenies, Minamiyutaka was selected and released(Onoet al.y1977).
Since K123 is resistantto root knot nematode and root lesion nematode,
Minamiyutaka is also resistant to those nematodes. In addition,
this cultivar shows
very high yielding
ability.
Most of the newly released cultivars
are related to hexaploidtypes of /.
trifida.
Tetraploidtypes of/, trifida collected in Colombia were used for widening
the genetic background of sweetpotato.
They are also resistantto root knot androot lesion nematodes.
They were crossed with sweetpotato
and back-crossed
three to four times to improved cultivars.
Lines obtained by back-crossing
weremorphologicallyand biologicallyalmost the same as sweetpotato(Miyazaki
et ah ,
1984, Chishiki
et al.y 1985).
Diploid
types of /. trifida
were used for thedevelopment of a tetraploid
type of sweetpotato(Kobayashi
and Miyazaki, 1976).
Conclusion
The importance of sweetpotato as a crop can not be estimated solely on thebasis of the past or present production and utilization
statistics.
The use of genetic
resources in breeding programs can contribute to the creation of new demands forthis important
crop. From this standpoint,
it is very important to make special
efforts to conserve sweetpotato genetic resources and ensure they are evaluated andused. We have to establishin vitro conservation and cryoconservation
systems tokeep and exchange sweetpotato genetic resources safely.
It is also important todevelop a technique for evaluating
the processing
quality.
Finally,
we need todevelop techniques,
which use new biotechnology
techniques,for breeding new

120cultivars

suitableto meet new demands of sweetpotato.

References
Chishiki,T., Komaki, K. and Miyazaki, T. 1985. Breeding use of wild tetraploid
species closely
related to sweet potato by continuous backcrossing.
2. Changes of some economic charactersas backcrossing
advances. Kyushu Agriculture
Research 47:56(inJapanese)
Iwanaga, M. 1987. Use of wild germplasm for sweet potato breeding.
Pages 199-210 in Exploration,
maintenance, and utilizationof sweet potato genetic resources. Report of the First Sweet Potato
Planning Conference. International
Potato Center(QP),
lima, Peru.
Jones, A 1967. Should Nishiyama's
K123 (Ipomoea trifida) be designated/. batatas')
Econ. Bot.
21:163-166
Kobayashi,
M. 1984a. Satsumaimo no kita michi(Sweetpotato-where it comes from?-).
Kokinshoin,
Tokyo, Japan, (in Japanese)
Kobayashi, M. 1984b. The Ipomoea trifida complex closely related to sweet potato. Paper presented
at Sixth Symp., Intl Soc. Trop. Root Crops, lima, Peru.
Kobayashi, M. and Miyazaki, T. 1976. Sweet potato breeding using wild related species. Proc. 4th Int.
Symp. Trop. Crops 1:53-57
Miyazaki,T., Chishiki,
T. and Komaki, K 1984. Breeding use of wild tetraploid
species closely
related to sweet potato by continuous backcrossing.
1. Relationshipbetween backerossgenerations
and crossing ability.
Kyushu Agriculture
Research 46:53 (in Japanese)
Nishiyama, I. 1971. Evolution and domesticationof the sweet potato. Bot. Mag. Tokyo 84:377-387.
Ono, T., Marumine, S., Yamakawa, O., Hirosaku, S., Sakamoto, S. and Ide, Y. 1977. A new sweet
potato variety, Minamiyutaka.
Bull. Kyushu Agric. Expt. Stn. 19:133-150(in Japanese)
Sakai, K, Marumine, S., Hirosaku, S., Kikukawa, S., Ide, Y. and Shirasaka, S. 1967. On the newariety of sweet potato, Koganesengan. Bull. Kyushu Agric. Expt. Stn. 13:55-68(in Japanese)
Shiotani,
I. 1983. A survey of habitats of Ipomoea trifida, a closely related species to sweet potato.
Rep. Plant Germ-plasm Inst. Kyoto Univ. 6:9-27

Maintenanceand use of sweetpotato

germplasm in China

XIAO-DING GUO, YI-HONG WANG,JING-YU WU, JIA-LIAN

SHENG1

Abstract
About 2,000 accessions of sweet potato are maintained in China. These accessions aremaintained in an active field genebank at Xuzhou in the north of China and at Ghangzhou in thesouth. The National Genebank in Beijing maintains in vitro plants. In recent years research on sweet
potato in vitro storage has intensified
in all three conservation centers. The main research areas havebeen meristem culture, plant regenerationand the technical conditions for in vitro germplasm storage.
This paper reviews the use of sweetpotato germplasm in China in the following areas: germplasm
evaluation, local cultivars, introductions,improved varieties, wild relatives,mutants, breeding lines
and virus free sweet potato production.
Recent research results are also presented.

Introduction
Sweetpotato was introduced into China in the late sixteenth century via tworoutes: one from Vietnam and Burma to south China (Yunnan and Guangxi
provinces) and another from the Philippines
to Guangdong and Fujian provinces insoutheast China. Thanks to its high yield, nutritional
value, wide adaptabilitytodifferent
environments the sweetpotato
has been grown in many parts of China,
covering most regions of the country. The main production areas have been the
Yellow and Yangtze River Basins (Sheng et al., 1987). Currently sweetpotato ranks
fourth in China as a food crop after rice, wheat and corn. Sweetpotato
is grown
annually on six million ha of land(Table
1). China's productionin 1990 accounts
for 85% of the world total (FAO, 1992).
During the past decade, sweetpotato
has increasingly
been used as an
animal feed and as a raw material for industry.
Thus sweetpotato is becoming an
industrial
crop and it was classified
as such in the Eighth-Five-Year
National
Research Program. In the context of national development for low soil fertility
areas in the central and south China, sweetpotato has played an important role inmaking this area with poor soils productive.
Sweetpotato germplasm research has
intensified
in recent years.
China is in the Asia-Pacificsecondary center of origin for sweetpotato.
South China is in the tropical and sub-tropicalregion.
Where sweetpotato can

Xuzhou Sweetpotato
Research Center,
Xuzhou, Jiangsu 221121,
China

122

Table 1. Sweetpotato
P ro v in c e

production

A re a ('0 0 0 h a)in China in 1986
P ro d u c tio n ( '0 0 0 to n )H eb e i
Jia n g su
Z h ejia n g
A n hu i
F u jianS h an d o n g
H enanH ub ei
H un anG uan gd on g
G uan gx i
S ic h u a n
G u iz h o u
Sh aanx i

352
275
1 15
65 8
2 17
4 ,1 5 2
7 83
1 86
2 65
57 9
2 37
1 ,2 3 0
1 01
98

1 ,1 2 5
1 ,3 3 0
5 57
2 ,7 7 2
66 1
4 ,0 0 3
1 ,7 8 2
5 94
71
1 ,3 8 6234
3 ,8 2 028
20 9

T o ta l

9 ,2 4 8

1 8 ,5 7 2grow year-round and flower easily in South China.
South China has a vast
reservoir of sweetpotato
germplasm as a result of natural and artificalselection.
Landraces cultivatedin other areas for decades or hundreds of years also possess
desirablecharacters and also contributeto genetic diversityof the sweetpotatoinChina.
With increasing
latitudethis diversity
decreases.
80% of Chinas
sweetpotato genetic diversity
is found from the Yangtze River Basin south, while
to the north most germplasm is of improved varieties.
International
germplasm and informationexchange has been improved inrecent years with scientists from the International
Broad for Plant Genetic Resources(IBPGR),
the International
Potato Center (CIP), and the Asian Vegetable Researchand Development Center (AVRDC) visiting China. In 1987 collaboration
between
CIP and China was initiatedand CIP opened its regional office in Beijing.
The
contract and collaborative
projects
between CIP and the Xuzhou Sweetpotato
Research Center (XSPRC)
have focussed specificallyon sweetpotato germplasm
evaluation and use and has produced satisfactory
results.
Germplasm collecting

and maintenance1. Collecting
Early germplasm collecting
started in the 1930fs in Taiwan, Guangdong,
Sichuan and Jiangsu provinces.
This involved introducing
new materials andevaluating
local varieties.
From the 1950's
the Government organized twocollecting
expeditionsin the Southeast and Yangtze River Basin and to the northof the Yangtze.
A total of 1442 accessions were collected up to 1982, 1096 ofwhich were morphologicallycharacterised
and included in the Sweetpotato
Variety123

Catalog

publishedin 1984 by the XSPRC.
From 1987 to 1990, with funding
from CIP the XSPRC organizedcollecting
expeditions
to areas north of 46°N in Heilongjiangand south of 28°N in
Yunnan and Guizhou provinces.
A total of 200 samples were collected from theseareas (Wu et al., 1988; Wu and Wang, 1988).
Zhaoyuan 15 collected
from
Heilongjiang
and Puer Huangshanyu collectedfrom Yunnan have been used inbreeding and production thanks to their high yield and good quality (Wu and Guo,
1990).
Introductionof the sweetpotato
via international
channels has been
continuing.
Over 200 sweetpotatoes were introduced from the United States, Japan,
the Philippinesand other countries.
Over 100 were introduced from international
institutes
like CIP, AVRDC and the International
Institutefor Tropical Agriculture(IITA).
Now the China national sweetpotato
collection
consists of over 2000
accessions,
184 of which were included in the Annals of Chinese Sweetpotato
Varietiesedited by XSPRC and publish in 1993.
2. Maintenance
Before the 1970Ts sweetpotato
germplasm was maintained in institutions
which also conducted sweetpotato
breeding
and research.
In the 1980fs anationwide
germplasm network was taking shape with XSPRC as the leading
maintenance center coordinating
23 institutions
around the country.
Due todifferencesin agroecologicalconditions,sweetpotato
accessions were maintained
nationallyin three institutions.
1). Germplasm Nursery at XSPRC maintains, in the field genebank, theaccessions from the Yangtze River Basin (and the region to the north)andintroductions
from Taiwan and international
institutions
around the world.
2). The sweetpotato germplasm misery in Guangzhou maintains materials
from the southern sweetpotato
growing area where sweetpotato
is grown as anautumn/winter crop. Guangzhou has a field genebank and maintains germplasm in
the form of root and storage organs.
3). The National Genebank in Beijing maintains in vitro sweetpotato plants
provided by XSPRC and Guangdong Academy of Agricultural
Sciences (GAAS)
in Guangzhou.
Once the in vitro storage system has been completed XSPRC will be
responsible
for the in vitro maintenance currently
carried out by the National
Genebank. At the moment, around 1000 accessions are maintained in each of thesethree institutions.
A small number of materials are maintained at some breeding
institutes.

1987;
plants(1) Field maintenanceThis method is technicallysimple and a viable method(Fernandes
et al.,
Human, 1987; Takagi, 1987) also evaluation
can be done on field grown(Yakuwa and Oka, 1987).
XSPRC grows about 1400 accessions annually in

124

the field. These accessions are stored in storage houses with a temperature of 13°C
to 15°C and relative humidity of 80% after curing. A storage house for long termroots storage is also being planned for construction.
Once completed the roots will
be stored for two years to reduce labor and land costs involved in the traditional
field maintenance system and minimize the risk of mixing up the accessions anddisease infection.
Field maintenance using stem cuttings and storage roots is economically
acceptable in China because of its low cost. However, maintained accessions areoften subjected to environmental stresses like drought, water logging, frost and alsodiseases.
On the other hand, accessions unable to produce storage roots undernatural conditionsin the maintaining
region cause difficulty
in storage and hence
maintenance. Mechanical mix-up is another problem in the planting-harvestingstorage cycle (see also Jarret and Florkowski,1990).
Increasingly
severe virus diseases in recent years have also been a threat tofield maintenance.
Virus free plants produced by meristem tip culture could be
infected again when planted in the open field. Data from our nursery shows that
85% of the accessions displayed
symptoms typical of virus infection(Table 2).
The fact that sweetpotato is clonally propagatedalso favors virus transmission
andaccumulation in plants.
Some accessions were lost due to virus infection which
results in no storage roots being produced. This has been a problem for germplasm
conservation for years. Infection could also affect evaluation for yield and disease
resistance (Liao et al., 1983; Yang et al., 1991).
(2) In vitro maintenance
Sweetpotato plants maintained in vitro are usually derived from meristem
tip culture and free from virus and Qther pathogens like fungi, bacteria, nematodeand mycoplasm-like organisms and facilitates
germplasm exchange and distribution
regionallyand internationally(Fernadez et al., 1987; IBPGR, 1987; Jarret, 1987;
Table

2. Accessions with symptoms typical of virus infection
nursery at Xuzhou Sweetpotato research Center during
Y e arN osu. ac
rv ce
ey ssio
ed ns

1982
1983
1984
1985
1986
1988
1989

530
575
590
590
669
8 17 (2 )1127

wN itho . a sy
cc messp toio mn ss

39
42
70
119
580
958

in germplasm
1982-1989 (1).
In terafe ctio
( n

1 .5
6 .8
7 .1
l l .71 7 .87 1 .085 .0

1) The first accession found with leaf roll symptoms was Jewel in 1981.
Jewel was introduced from the US.
2) Nursery plants were surveyed. Others were surveyed in the field.
Data for 1987 is not shown.

125

Kuo, 1991; Lu and Chen, 1985; Ouyang, 1984).
Research initiatedin themid-1980fs
on tissue culture in China has centered on four area.
a). Meristem tip culture and plant regeneration.
Meristem tip was obtained from field plants or sprouts on the roots in an
incubator.
Basal MS or 1/2MS was supplemented with plant hormones in different
concentrations.
Optimum concentrationof carbon sources (sucrose and glucose) is
3% and sucrose is better than glucose (Lu et al., 1981).
It usually takes two or
three months to regenerate new plants (Xin, 1987).
Regeneration
time could be
affected by sterilizingtime of explants, concentrationsof sterilizing
solution,
agar
quantity
added (Chen et al., 1989)
and more importantly
by hormones and theirconcentrations(Chen et al., 1989; Tang et al., 1989; Xin, 1987)(Table3),
genotypes used (Table 4), explant size, physiologicalstage of plants and culture
environment (temperatureand light) (Xin, 1989a).
Merstem tips from apical tips
and up to three buds down were found to be easier to regenerate than from otherpositions.
Under optimal conditions,
meristem tips with 2-3 primordia can be
induced to regeneration
for most genotypes.
Culture temperature can range from 28°C to 30°C; growth will be retarded
when temperature is below 24°C. When it is above 30°C the meristem tip underculture will turn brown from initial green before it dies (Xin, 1989b).
Results fromour laboratory
indicate that meristem tips excised from sprouts of incubated roots
are better for cultures' growth and plant regeneration
than those from field plants.
In addition,
spring is the best season to culture the meristem tip in vitro.
Table 3. Effect of hormones on shoot formation
tip culture of sweetpotatoes(l)B a salTable

from apicalH o rm on es (m g yl)

meristem

P la n t

m e d ia

BA

K T

IA A

re g en eratio n (% )M S or
1/2 M S

00 .5

2 .0
0 .2
.5

0 .5
01.0
.2

66 ‑706 0 ‑ 728 05

1) After

7-14 days transfer

4. Plant

regeneration

Range of regeneration
61-10051- 6031- 50ll- 30

to 1/2MS.

rate of30 genotypes(%)

cultured

No. of varieties
22
5
2
1

on the same medium
Percent
77.3
16.7
6.7
3.3

126

(3) In vitro storage.
There are two methods to maintain in vitro cultures:
minimal growth andcryopreservation.
Regenerated plants were propagated by nodal cuttings and moved
to storage room when the plantlet
is 3-4 cm. In vitro plant growth was controlled
by additionof retardants in the media and regulationof light (intens ity and period)and humidity.
Growth retardants
added are usually kinetin (KT), abscissic
acid (ABA),
glyphosate,
cycocel (ccc), methyl succinic acid (MSA) and N-dimethyl
succinic
acid (B9) (Wang et al., 1989; Xin, 1989a;
Zhou, 1989).
These inhibitors
canreduce culture's growth during storage (Table 5) but the effect could carry over tothe next subculture, to which no inhibitors
were added. Among them ABA can stillslow subcultures
growth for 3-6 months. Glyphosate
treated subcultures
show
mild chlorosis in the leaves and those in KT treatment could produce callus on the
cut surface. High concentrationof inhibitors
can induce mutation (Xin, 1989c).
Mannitol could also be added to produce osmosis in the medium and reduce theroots ability to uptake and hence cultures growth. As a monosaccharide derivative,
mannitol is better than sucrose in this respect.
It has been reported that with aconcentrationof 10g/l of mannitol survival of in vitro plants was 69.9% after one
year's storage (Xin, 1989a).
Lower temperatures (16-18°C)
is a simple way to control in vitro plant
growth. It is a convenient method for maintenance, especiallywhen combined withgrowth inhibitors.
Optimal light conditions
with an intensity of 1000 lux in 8 hours
daily and humidity of 50-60% (RH). When RH is over 65% contaminationcanoccur due to favorable humidity
for fungi spores and bacteria in the air. In our
experience, use of tin foil as seals allows both gas exchange and moisture retention
and prevents contamination.
c) Genetic

stabilty.
Callus formation should be minimal to avoid genetic variation.
However,with the time of maintenance in vitro variation
can more easily occur, no matter
what media are used (Ng and Dodds, 1987).
Sweetpotatoes
stored in media with
Table 5. Effects of five growth inhibitors
on in vitro survivalof sweetpotatoes
on MS medium
G row thinh ib itors
A B A( A b scissic acid)
G lyp h osate
K T (K inetin )cccTC y coc el)
cccfC y coc el)
M ann ito 1
CK

C o ne .
(m g /1)

N o . o f vais.
testedSu rv iv al after on e
years in sto rag e i

1
1
10

10
10
20

8 5 .58 4 .87 1 .310 0
50 0
10 ,00 0
M S on ly

10
10
20
20

3 7.7
8 9 .4
6 9.9
5 1.5

127

Table

6. Effect of growth inhibitors

G row thin h ib ito r
K T
M an n ito 1
A BA

C on e.
(m g /1)

on vine color of Xushu 18

R o o t y ield
(g /p lan t)

V in e c o lo r

106

4 52 0GP urerpenlish red

15 ,0 0 0
3 0 ,0 0 0
1 01

410
100
275
30

P u rp lish red
G ree nGP urerpenlish red

Note: Plant was cultured on MS medium. Data were gathered in thefield where in vitro plants were transplanted.
Per plant root
C K yield Mwas
S oaveragedn ly
P u rp lish red
over five3 8 0plants.

KT, mannitol and ABA for one year showed slowed apical growth and shorter vines
one month after transplanting
in the field.
Plant growth becomes normal threemonths later (Xin, 1989c).
At high concentrations,
growth retardants
can cause
morphologicallychanges. Xushu 18 treated with high dose of the inhibitors
havea green vine compared with the original color, purple (Table 6). However, somevariationis temporary since treated plants may return to normal after one growth
cycle, especiallyfor the colors of leaf, vine, skin and flesh of sweetpotatoes
treatedwith mannitol (Wang et al., 1989).
Other authors also suggested that these typesof variation are temporary and not heritable.
It is safer to add 0.5-1.0% mannitol(w/v) in maintenance media to minimize the possibilityof morphologicalor genetic
modifications.
d) Maintenance and management.
Attention should be paid to the following:a) the storage room should be thoroughly
sterilized
before use by
fumigating
the room with potassium permanganate mixed with methanol.
b)Relative
humidity should be controlled
at 50-60% especiallyduring thesummerc) The room should be periodicallyventillated
to allow air exchange withthe outside in order to reduce carbon dioxide release by dark respirationandethylene.
d) subculture materials that are already maintained sufficiently
long and that
do not grow well.
e) Maintainedmaterials should be arranged in such an order that checking
and recording can be conveniently
undertaken.
Germplasm

evaluation

Evaluationof germplasm

is importantfor production

and breeding.

We

128

have evaluated germplasm based on yield, quality(dry matter, starch content,soluable sugar, crude protein, crude fibre, vitamin C and carotene), disease and pest
resistance(to root rot, black rot, stem nematode and root-knot nematode in thenorth and to bacterial
wilt, stem rot and weevil in the south), stress tolerance(drought,
cold, salt excess moisture)and storability.
Evaluation has identified
a number of accessions with desirable
characters.
Some of them are :a) high-yield
whose storage root yield approximatesor exceeds the local
control: Xushu 18, Fengshoubai,
Nongdahong, Yubebai and Pengwei.
b) High dry matter content: based on results from 547 accessions evaluatednationally23.9% have a DM content over 30%. Examples are Manicunxiang,
Yangaofen, Lizixiang,
Benikomachi,
L-4-5.
c) Good quality:
Lizixiang,
Yanshu 3, 51-16 and Beijing 553 have a goodeating quality while Centenial,
Caromax, Dananfu, Yizi 138 and Beijing
284 havea high carotene content.
d) Huabei 256, Hebei 351, Liaoshu 205 and Shaashu 1 have good
germinability,
which is important in the north where planting materials are obtained
from propagules
sprouted from bedded storage roots.
e)Early maturity:
Huabei 52-45, Jishu 872 and Ningyan Sanshiri Zao. Thisis important to permit multiple
cropping.
Accessions resistant to pests and diseases were also identified:a)Black rot: Xiaobaiteng,
Jiagou Dazi and Tiexianteng;b)Root rot: Xushu 18, Xu 236 and Licunhuang;c)Stem nematode: Yanshu 6, Qingnong 8 and Jishu 10;d)Root-knot
nematode: Suxian Xiaohuaye,Qingnong
2 and Hongtou;e) Bacterial
wilt: Huabai 48, Xiangnong Huangpi and Yongshu 2;f) Stem rot: Yanshu 5, Honghong 1 Peiwei;g) Sweetpotato
weevil: Huabei 117, Biaoxinhong
and Tainung 31.
Accessions tolerant to environmental
stresses are:a) drought tolerance:
Tiedingfan,
Beijing 553, Nongdahong and Jishub) cold: Dongshu, Huihongzao, Jiucaizhong
and Yanshu;c) salt: Hongshashu,
Baipi, Liushiri,
Shaanshu 1 and Lushu 1;d) excess moisture: Niaoyaoli,
Baigu Qilong and Yubeibai;e) good storability:
Zhoushu 13, Tainung 27, Lizixiang
and Xindazi.
Germplasm

2;

Use.

1) Local varieties.
Four hundred years of cultivation
has produced a diversityof sweetpotatoes
through natural and artificalselection.
These landraces are adapted to the local
environment and are grown for their disease resistanceand good quality.
They

129

have also contributed
to many successful breeding
programs.
Landraces like
Yubeibaiand Pengwei from Guangdong, Hengjin from Taiwan Xiaowuchi from
Fujian conferred high-yieldand drought tolerance genes to improve varieties
Fengshu 1, Fengshoubai,
Ningshu 1 and Yanchihong.
Mancunxiang of Guangxi,
Hongpi and Hongxin of Zhejiang,
Xiaobaitengfrom Jiangsu and Xijiaozhong
from
Beijing have helped improve dry matter(DM)content in Shijiazhuang
419, DM andgerminability
in Honghong 1, DM and eating quality in Yan 78-384 and sweetness
in Huabei 166 (Sheng et al., 1987).
Xushu 18, accounting for over 50% of
sweetpotato production area nationallyhave the genetic background of Anhui local
variety, Jiagou Dazi. Likewise, Lushu 5 and Mianfen 1 bred in Shandong andSichuan has genes from Pengwei (a Guangdong
local variety)and Suxian
Xiaohuaye (an Anhui local), respectively(Wu et al., 1993).
Some other local varieties
with superior characters are:a) Guangdong's Baigu Qilong and Xiaoshengzhong
which are resistant toroot rot, a disease that never occurs in Guangdong;b) Zhejiang's
Tieding fan which is highly tolerant to drought;c) Guangdong's Fenghuangfu Zhong which has high dry matter content of
38-40% when grow locally;d) Hubefs Dabaishao which is highly tolerant to salt (Guo et al., 1993).
2) Introduced
germplasm.
This germplasm has contributed
to the diversityof China's sweetpotato
genetic resources.
Okinawa 100 from Japan and Nancy Hall from the US stillaccount for over 14% of the total sweetpotato
production
area. Okinawa 100 isgrown around the country and has been used as a parent for 41 improved varieties
while Nancy Hall was used as a parent for 33 varieties.
Crosses between the twohave resulted in the release of 31 official
varieties(Lu, 1990).
Newly-released
varieties
Nanshu 88 and Lushu 3 were selected from progeny of America Red, Yi
306 and Sushu 2 from Minamiyutaka.
High carotene germplasm from the USA and AVRDC like Caromex, Painter, NC
345, Centenial and AIS 0122-2 have produced some good crosses with progenies
of good quality.
Clones with high anthocyanin
have been selected from crosses
between Yaamkawa Murasaki from Japan and Rosa from Brazil, which could be a
way to diversify
the use of sweetpotato in China.
3) Improved varieties and breeding lines.
Many officiallyreleasedvarieties
are selectedfrom parents whichthemselves were the result of genetic improvement. They are agronomicallywell
accepted and usually used as parent material again. National breeding programs
have about 30 combinationsof this nature. Thirty-one varieties released in the pastten years were from improved parents. Some improved varieties are used as parents
because they can easily flower in the north, like Qinshu 2, Xiangyanghung,Gaozi
1 and Hebei 351.

130

Many superior varieties
produced from breeding are maintained
as part of
the germplasm collection
and are later used as parents.
Nationally
we harvest
hundreds of thousands of hybrid seeds and a good number of advanced materials
from those seeds have been used in sweetpotato improvement. The high-starchcontent Mianfen 1 was selected in a cross between two advanced clones 79-14 and79-96 (Bi et al.,1988).
Advanced line 77-98 produced Jishu 2, a variety with highDM and resistance to black rot (Wang,1988).
4) Wild

relativesof sweetpotato.
Wild relatives of the sweetpotato are important sources of genes for disease
resistanceand quality.
After release of Minamiyutaka
from /. trifida in Japan,
Chinese scientists
have also incorporated
K123 (/. trifida)in their breeding
programs and have used the progeny as parental materials.
Clones selected fromsuch crosses like Guangshu 80-117 and Jinshu 83-91 are resistant.tobacterial
wilt
and tolerant to cold in addition to having good storage ability (Li et al., 1988). B
58-5 as selected in Jiangsu Academy of Agricultrural
Sciences (AAS) from (wildrelative X sweetpotato)
X sweetpotato backcrosses is highly resistant to root rot andhas a dry matter content of 32-36%(Zhang
et al. 1987).Shandong
AAS also
selected seven clones using a wild relative as a parent, which was highly resistant
to stem nematode (Chang et al.,1993).
As a new variety bred by Zhejiang AAS,
Zheshu 2 is a descendant of a Uganda morning glory.
5) Mutation.
Bud sporting in sweetpotato
usually occurs under natural conditions.
Betterclones can be selected from such mutation.
Xu 77-6 resulted from a sport in
Xushu 18 and has a more vigorous growth, higher yield and better quality than theoriginal Xushu 18. From mutations of Minkang 329 which is resistant to bacterial
wilt, Minkang 330 was selected, which also has resistanceto stem rot and highyield (Zhang and Chen,1990).
Induced mutations are often used for germplasm enhancement. Beijing
Agricultural
University(BAU) applied electron beams onto sweetpotato true seeds
and found in the offspring some individuals
with increased DM (Li et al., 1988).
They also irradiatedwith Cobalt 60, the shoot tips of Xushu 18 which is susceptible
to black rot and obtained two Xushu 18 lines with resistance to the disease (Lu etal., 1987). Other workers also applied fast neutron on true seeds and were able toselect lines with high starch content and resistance to black rot (Cui, 1987).
Those
materials can be used in production and breeding.
6) Virus

free Sweetpotato production.
This work has just started using sweetpotato
plants regenerated
frommeristem tip culture. Field virus surveys indicate that there are two primary viruses
in China: Sweetpotato
Feathery Mosaic Virus (SPFMV) and Sweet Potato Latent131

Virus (SPLV). Sweetpotato virus elimination
can produce significantly
higher yieldand much better looking storage roots (Yang et al., 1991).
Sweetpotato germplasm has been used mostly in genetic improvement of
the crop. More extensive research is warranted to ensure full use is made of theconserved germplasm. International
exchange has been limited by some factors.
Introductionof sweetpotatoes from other countries especiallyfrom South America,
the primary center of origin will prove necessary for the crop's future in China. An
improved quarantine system necessary. Biochemical and physiologicalevaluationof germplasm should be on the research agenda and the best germplasm should berecommended to either farmers or breeders. Interdisciplinary
research will be
another step forward for sweetpotato germplasm research.
These will make thesweetpotato more versatile for human and industrial use.
References
Bi, C.X. and M.B. Peng. 1988. High starch content sweetpotato variety "Mianfen 1". Chinese
Sweetpotato
Journal 2: 124-125 (in Chinese)
Chang, C.X., Q.M. Wang and J.J. Wang. 1993. Preliminary
study on resistanceto root knot nematodein sweetpotato
germplasm in Shandong province. Chinese Sweetpotato Journal 5-6: 14-16(in Chinese with English summary)Chen, Y.D., X.J. Zhang and Z.X. Fang. 1989. The methods of meristem tip culture of sweetpotato.
Pages 27-31 in A Treatise on Storage of Crop Germplasm Resources. Academic Book &Periodical
Press, Beijing,
China (in Chinese with English summary)Cui, G.Q. 1987. Mutation breeding using fast neutron attacking on adventitious
bud from hypocotyl.
Chinese Sweetpotato
Journal 1: 93-95 (in Chinese with English summary)Dodds, J.H. 1987. Review of in vitro propagationand maintenance of sweetpotato
germplasm. Pages
185-192 in Exploration,
Maintenance and Utilizationof Sweetpotato
Genetic Resources.
International
Potato Center, lima, Peru
FAO Basic Foodstuffs
Service/Commodities& Trade Division.
1992. The World Sweetpotato
Economy. FAO, Rome, Italy 35p
Fernandez, G.C.J., J.H. Lu and Y.K. Huang. 1987. Status of sweetpotato
collections
maintainedat
AVRDC. Pages 129-140 fin Exploration,
Maintenance and Utilizationof Sweetpotato
Genetic Resources. International
Potato Center, lima, Peru
Guo, X.D., J.Y. Wu and L.X. Zhu. 1993. Evaluation
for salt tolerance in sweetpotato
germplasm
nursery. Journal of Alkaline Land Use 2:36-41 (in Chinese)
Human, Z. 1987. Current status on the maintenance of sweetpotato germplasm. Pages 101-120 in
Exploration,
Maintenance and Utilizationof Sweetpotato
Genetic Resources. International
Potato Center, Lima, Peru
IBPGR. 1987. Meristem-tip
culture and virus indexing of sweetpotato.
IBPGR, Rome, Italy 46p
Jarret, R.L. 1987. U.S. sweetpotato
repository.
Pages 121-128 in Exploration,
Maintenance andutilizationof Sweetpotato
Genetic Resources. International
Potato Center, Lima, Peru
Jarret, R.L. and W.J. Florkowski. 1990. In vitro active vs. field genebank maintenance of sweetpotato
germplasm: major costs and considerations.
Hortscience25(2):141-146
Kuo,G.C. 1991. Conservationand distributionof sweetpotato
germplasm. Pages??-??
in In vitro
methods for Conservationof Plant Genetic Resources. J.H.Dodds (ed). Chapman and Hall,
London
Li, W.J., Y.Y. Zhang and S.Y. Lu. 1988. Preliminary
study on sweetpotato radiated by electron ray.
Chinese Sweetpotato Journal 2:16-18(in Chinese)132

Li, X.Z. and Z.S. Wu. 1988. Use of Ipomea triflda (K 123) in sweetpotato
breeding.
ChineseSweetpotato
Journal 2:48-50 (in Chinese)liao, C.H., H.S. Tsay and Y.C. Lu. 1982. Studies on eradicationof SPV-A and SPV-N virus from
infected sweetpotato.
J. Agric. Res. China 31 (3):239-245(in Chinese with English
summary)
Lu, G.Q. 1990. Pedigree
of some improved Chinese sweetpotato
varieties.
Chinese Sweetpotato
Journal 4:26-29 (in Chinese)
Lu, S.Y., C.G. Wu, W.J. li and Q.H. Fang. 1987. Radiating
sweetpotato
with Co 60 produced
resistantmutant. Chinese Sweetpotato Journal 1:172 (in Chinese)
Lu, X.H. and Y.C. Chen 1985. Studies for obtainment of sweetpotato mycoplasm like organism freeseedlings
by shoot tip culture method and its available
identification.
Acta Agronomica
Sinica ll (3): 191-197(in Chinese with English summary)Lu, Z.X., M.S. Wang and J.G. Dong. 1981. The influence of carbon sources on formation and growthof root tuber callus of sweetpotato (Ipomea batatas Lam.). Acta Phytophysiologia
Sinica 7(2):105-lll(in Chinese with English summary)Ng, S.Y. and J.H. Dodds. 1987. In vitro methods for pathogen
eliminationand international
distributionof sweetpotato germplasm. in Exploration,
Maintenance and Utilizationof Sweet
Potato Genetic Resources, p.323-329,
International
Potato Center, lima, Peru
Ouyang, S., R.S. Wang and X.Y. Zhang. 1984. Sweetpotato meristem-tip
culture and eliminationofdwarf pathogen. J. Fujian Agric. Sci. & Tech. 2:19 (in Chinese)
Sheng, J.L., Y.H. Wang and Q.H. Xue. 1987. Sweetpotato research and production in China. Chinese
Sweetpotato Journal 1:1-5 (in Chinese)
Takagi, H. 1987. Sweetpotato
collectionsin Papua New Guinea. Page 129-140 in Exploration,
Maintenance and Utilizationof Sweetpotato.
International
Potato Center, lima, Peru
Tang, J., Y.H. Wang, X.D. Guo and J.Y. Wu. 1989. Meristem-tip
culture of sweetpotato.
Pages 32-36
in A Treatise on Storage of Crop Germplasm Resources. Academic Book & Periodical Press,
Beijing,
China (in Chinese with English summary)Wang, S.F. 1988. New sweetpotato variety, Jishu 2. Chinese Sweetpotato
Journal 2:50 (in Chinese)
Wang, Y.H., J. Tang, X.D. Guo, J.Y. Sun and J.Y. Wu. 1989. Preliminary
study on genetic stabilityof sweetpotato(Ipomea batatas Lam.) maintained in vitro. Pages 204-208 in A treatise on
Storage of Crop Germplasm Resources. Academic Book and Periodical
Press, Beijing,
China (in Chinese with English summary)Wu, J.Y., X.D. Guo and Y.H. Wang. 1988. Sweetpotato collection
and production
survey in Yunnan
Province. Chinese Sweetpotato
Journal 2:1-4 (in Chinese)
Wu, J.Y. and Y.H. Wang. 1988. Sweetpotato
collection
and production
survey in Heilongjiang
Province.
Chinese Sweetpotato Journal 2:5-7 (in Chinese)
Wu, J.Y. and X.D. Guo. 1990. Some superior local sweet potato cultivars. Chinese Sweetpotato
Journal 4:156-157(in Chinese)
Wu,J.Y., G.Q. Lu, J.L. Sheng and B.F. Song. 1993. Progress on sweetpotato germplasm research in
China. Chinese Sweetpotato Journal 5-6:3-7 (in Chinese with English summary)Xin, S.Y. 1985. Maintaining
sweetpotato
germplasms by tissue culture. Crop Genetic Resources
3:24-26 (in Chinese)
Xin, S.Y. 1987. Sweetpotato meristem-tip
culture and in vitro storage. Crop Genetic Resources.3:2426 (in Chinese)
Xin, S.Y. 1989a. Technology
and conditions
for germplasm preservationof sweetpotato(Ipomeabatatas Lam.). Pages 2-9 in A Treatise on Storage of Crop Germplasm Resources.
Academic Book & Periodical
Press, Beijing,
China (in Chinese with English summary)Xin, S.Y. 1989c. Effects of chemicals on the preservationof sweetpotato
germplasm. Pages 10-15
in A Treatise on Storage of Crop Germplasm resources. Academic Book and Periodical
Press, Beijing,
China (in Chinese with English summary)133

Xin, S.Y. 1989b. Meristem culture of sweetpotato.
Pages 27-31 in A Treatise on Storage of Crop
Germplasm Resources. Academic Book & Periodical Press, Beijing, China (in Chinese withEnglish summary)
Yakuwa, H. and S. Oka. 1987. Maintenance of clonally propagatedcrop germplasms by in vitro
methods. Agricultureand Horticulture62(12):1343-1347.
(in Japanese)
Yang, Y.J., J.Y. Xing and C.L. Zhang 1990. Survey on sweetpotato virus diseases. J. Jiangsu Agric.
Sci. 2:33-34 (in Chinese)
Yang, Y.J., J.Y. Xing, J.Y. Wu, J. Tang and X.D. Guo. 1991. Yield increase of virus-freesweetpotatoes.
J. Jiangsu Agric. Sci. 4:38-39(in Chinese)
Zhang, L.S. and Q.H. Chen. 1990. New sweetpotato resistant to bacterial wilt, Minkang 330. Chinese
Sweetpotato
Journal 4:147-148(in Chinese)
Zhang, L.Y., P.L. Xu and R.L. Qui 1987. Collection
and utilizationof wild relativesof sweetpotato.
Chinese Sweetpotato
Journal 1:26-29 (in Chinese)Zhou, M.D. 1989. The effects of methyl succinic acid on growth and preservationof plantlet ofsweetpotato
in vitro. Pages 17-20 in A Treatise on Storage of Crop Germplasm Resources.
Academic Book & Periodical
Press, Beijing,
China (in Chinese with English summary)The Use of Sweetpotato
Japan

Genetic

Resourcesin Breeding

in

OSAMU YAMAKAWA1

Abstract
The use of genetic resources in sweetpotato breeding started with domestic accessions, andthen involved introduced cultivars and wild relatives. Initiallythese materials were crossed directly
to each other. In the next stage of breeding parental lines with high inbreeding
coefficientswere
produced by selfing,
full-sibor half-sib
crossing. These lines with different
origins and highcombining ability were crossed one by one to find high heterosis. Wild relatives were back-crossed
to elite cultivars several times to get storage root formation before attempting a breeding program.
Recently the polycrossmethod has been adopted using this method many accessions are crossed
simultaneously.
To use this system widely, it is necessary for cultivars to flower or to develop grafted
stocks which results in flowering.

1. Historyof Sweetpotato

Breeding

in Japan

It is said that sweetpotato was introduced to Japan about 400 years ago. The
maximumacreage of sweetpotato (Ipomoea batatas LAM.) was 450,000 ha in 1950,
but it began to decrease in 1965 and the acreage in 1993 was only 55,100 ha.
Farmers selection started at the same time as farmers first grew the crop, but there
are no records of sweetpotato
selection before the end of 19th century.
Sakai (1989)
classified
sweetpotato
breeding in Japan since 1890 into five
periods:
The first period from 1890 to 1912 involved the breeding of the promisingcultivars
by farmers, who collected
domestic or foreign cultivars
or spontaneous
mutants and selected the best cultivars
from these materials. During this period"Beniaka", "Genji" and "Sichifuku"
were released.
The second period from 1913 to 1936 was the start of systematic breeding,which was supported by the government. During this period various domestic
cultivars were crossed and "Okinawa No.100", an important cultivar, was released.
The third phase of sweetpotato
breeding, from 1937 to 1956, involved theestablishment
and developmentof a breeding system or network, in which therelationshipbetween each experimental stations was clarified. During this period 20
registeredcultivars
were released, among which "Gokokuimo", "Norin No.l",

Kyushu National Agricultural
Experiment
Miyakonojo,
Miyazaki 885, Japan

Station,136

Figure1.

Production
cultivars

rateof acreage

per each sweetpotato"Norin No.2" and "Kokei No.14" are the most famous ones. The most importantregisteredcultivars("Okinawa No.100", "Gokokuimo", "Norin No.l" and "Norin
No.2") occupied 70% of the cultivatedacreage by the end of this period (Fig.l).
During the fourth period from 1957 to 1974, most attention was paid to theimprovement of breeding
methods and using the foreign
genetic
resources.
"Tamayutaka", "Ariakeimo" and "Satsumaaka" were released in the beginningof
this period
as a result of breedingin the former period. However breeding
efficiency
decreased gradually
due to the narrow genetic background leading to
inbreeding
depression.
There were only five ancestors of the leading cultivars grownat that time. These were "Shichifuku","Choshu","Genki", and "Yoshida","Benikawa" (Sakai, 1965). Therefore many introduced cultivars and wild relatives
were introduced
into
crossing
programs
to broaden
the genetic
base.
"Koganesengan"and "Minamiyutaka"were released
as the resultsof using
introduced
germplasm (Fig.2).
The fifth period from 1975 to the present the sweetpotato
breeding focussed
on breeding cultivars
for new foods and sweetpotatoes
which require little labor
inputs. "Benihayato"(Sakamotoet al., 1987) with high carotenoid
content and137

Figure 2.

Table

The pedigree of "Minamiyutaka"species (Ipomea trifida, 6x)

derived1. Caroteniodof "Benihayato"and polyphenol

content

Table 2. Beta-amilase
activity
and maltose content
before and after cooking (1983-85)

from a wild

(1984)of "Satsumahikari""Satsumahikari"(Kukimura et al., 1989) with low maltose have been released(Tables
1 and 2). "Naeshirazu"(Shikata,
1976) was released for direct plantingasoccurs with potato. "Beniazuma" and "High Starch" (Tarumoto et al., 1989) werereleased for table use and starch industry,
respectively.
There is recent interest in
developing
low starch cultivars with high color pigment, which could be used asa substitutefor as potato and carrot. For this introduced
genetic resources will bevery useful, because they generally
have low starch and low sugar content.

138

2. Inbreeding

Methodfor Using

Genetic

Resources

Since Sakai (1964)
showed that starch content is mainly governed bypolygenes with additive effects and root yield by genes with non-additiveeffects,
the most commonbreeding method in 1970,s used inbred lines with high starch andtest combining ability. Domestic and introduced cultivars were inbred by selfing or
sib-crossing.
According to Yunoue (1967) and Yoshida (1986),
both seed setting
rate and plant vigor decreased rapidly when the inbreeding
coefficientbecame close
to 0.2. From my own experience, inbreeding
depression
made it difficult
tomaintaininbred lines and hybrid
seed set between inbred was sometimes
impossible.
The most successful
cultivarbred by this inbreeding
procedureis"Shiroyutaka"(Sakamoto,1987) for the starch industry.
Its maternal parent has"Kanto No.33" three times in its ancestory before its grandparents
generation.
"Beniazuma" and "Fusabeni" released for table use have grandparent
as an inbredline. "High Starch" with the highest starch content, one of the great grandparents
is an inbred line.
Yamakawa et al. (1977)
crossed inbred lines from a sib-crossed
seriesderived from different
origins (domestic,
introduced and wild) with several testers
which has no relationshipwith crossed partners, and compared the progeny meansfor dry matter content and root yield among crosses. The results showed that
improvement of dry matter content by inbreeding
was not clear and the decrease ofroot yield by inbreeding
depression
could not always be recovered by heterosis. The
inbreeding
method have some success but is not used now.
3. Backcrossing

Methodfor Using

Wild

Relatives

The use of wild relatives of sweetpotato in sweetpotato breeding started one
year after Nishiyama
introduced
one accession (Ipomoea trifida DON.) from
Mexico to Japan in 1956 (Nishiyama,1963). Sweet potatoes are usually used asrecurrent parents in backcrossing
with wild relatives.
Undesirable
traits of wild
relatives were eliminated by repeated backcrossing
and useful traits accumulated by
selection.
In the first backcross the progenies
still showed the wild traits such as
slender twining stem. But in the second backcross their morphologicaltraits were
almost similar to those of sweetpotato(Sakamoto 1970).
Yamakawa and Sakamoto (1978)
studied the number of backcrosses andpractical
traits like root yield and dry matter content using several Fl, Bl and B2lines derived from two triploid and hexaploid accessions of/, trifida, K223 (3x) andK123 (6x). The Fl hybrid lines had the highest root yield, but the lowest dry matter
content. Progeny tests showed that the combining ability of root yield and dry
matter content improved from Fl to B2 generation (Fig.3).
From these results, it isrecommended that more than two backcrosses should be undertaken along with theselection for root yield and dry matter content.

139

Figure3. Relationshipbetween the times of backcrossing
and thepractical
traits when sweetpotato was backcross to /.
trifida (6x and 3x).
/. trifida (6x) series:/. trifida (3x) seriesshows parental lines:shows progeny means

As a result of backcrossing
during the last 20 years, excellent parental lines"LM17" (Fl hybrid
between K123 and "L-4-5")
and "Kyushu No.58M (Blgenerationof "LM17") were developed.
"Minamiyutaka",
which belongs to B2
generation of "Kyushu No.58", was released for the starch industry. This variety has
a 1/8 kinship relationshipwith /. trifida (6x) in its pedigree.
"Minamiyutaka"wasgrown 5,500 ha in 1978. At present "Shiroyutaka"and "Shirosatsuma"
havereplaced this cultivar,
but "Minamiyutaka"
is still a very valuable cultivar
withstrong resistanceto nematodes which is thought to have been inheritedfrom /.
trifida. Most cultivars except "Siroyutaka"
have "LM17" or an other Fl hybrid with/. trifida (6x) as an ancestor. Wild species introducedby Nishiyama have beenplaying an important role in sweetpotato
breeding in Japan. However, to date only/. trifida (6x) has lead to useful results.

4, New breeding

methods

for Using Genetic

Resources

Simple single crosses between unrelated or weakly related parents so thatthe the weaknesses and strengths of each parent are complemented is frequently
used. Yosida (1986)
calculated
inbreeding
coefficientsof all single
crosses
contained in the combining ability tests from 1961 to 1984 and showed that single
crosses with smaller inbreeding
coefficientthan 0.1 would have higher yielding thanthose with larger inbreeding
coefficientthan 0.2. About 90% of all breeding lines140

Breeding
procedure
for sweetpotatoes
proposedbyJones (1965).
Four generations without selection are necessary to establish
a randomly interbreedingbase population.
In following
generations,the base population
may be altered towardhorticultural
goals by selection.

with "Kyushu No." have an inbreeding coefficientof less than 0.1 (Yoshida1985).
Recurrent selection in sweetpotato breeding was first proposed by Jones(1965)(Fig. 4). In this procedure,
selection
should be avoided in the early
generations
in order to increase the frequency of effective
gene recombination.
Shikata(1980)
tried mass selection
for skin color and root yield after four
generationsof random mating. After three cycles of mass selection the skin color
converged to the desired objective
and root yield tended to increase.
Yamakawa and Sakamoto (1980)
proposed another procedure by using thepolycross method with naturally
flowering lines (Fig.5).
The individual
selection
within half-sib families selected using the combining ability test took the place of141

Figure 5. Breeding program in sweetpotato for breeding synthetic
cultivars
adapted to true seed planting(Yamakawaand Sakamoto, 1980)

simplerplanting

mass selection. After two cycles of selection the root yield under true seed
culture increased by some 15% per cycle (Yamakawa and Sakamoto 1987)
Shiga (1984)
proposed reciprocal
recurrent selection using polycross andparental line selection without using progeny test (Fig.6).
Katayama et al. (1991)
crossed two groups of the parental lines selected after three cycles of polycrossing
within each group (domestic and introduced),and concluded that progenies fromsingle crosses have smaller coefficientsof variation for root yield and dry matter
content than those from polycrossing,but they have higher means for both traits
than those from polycrossing.
Recurrent selection
is simpler
and more efficientmethod of using
sweetpotato germplasm. However it is not popular in sweetpotato breeding in Japan,
because there are no promising naturally flowering lines which is necessary for
random mating or polycrossing.
In place of using natural flowering lines, it ispossible to graft sweetpotato to morning glory (Pharbitisnil) to induce flowering.
But there are many difficulties in growing this morning glory in uncontrolled
conditions.
There are about 1,400 germplasm accessions in the Kyushu National
Agricultural
Experiment Station and a part of them have naturally flowering traits.
Weare trying to introduce this naturally flowering trait into superior cultivars andto develop good stocks of naturally flowering sweetpotato.

142

Breeding
procedure for sweetpotatoes
proposedby
Shiga (1984).
In the selection
year (2nd and 4th year) there are two
selections a year, because two crops per year become possible
owing to plastic multing culture.

References
Jones, A. 1965. A proposed breeding
procedure for sweetpotato.
Crop Sci. 5: 191-192
Katayama, K., Tamiya, S., Tarumoto, I. & Kato, S. 1991. Segregationof yield components insweetpotato
seedlingsof single cross and polycrossamong lines derived from maternal line
selection.
Japan J. Breed. 41 (Abs.2):
2-3 (in Japanese)
Kukimura, H., Yoshida, T., Komaki, K, Sakamoto, S., Tabuchi, S., Ide, Y. & Osamu, Y. 1989.
"Satsumahikari":
A new sweetpotato
cultivar. Bull. Kyushu Natl. Agr. Exp. Stn. 25 (3):225-250 (in Japanese)
Nishiyama, 1. 1963. The origin of the sweetpotato
plant. Pages 111-128 in J. Barrau (ed.) Symposium,
plants and the immigrationsof pacific people.
Ono, T., Marumine, S., Yamakawa, O., Hirosaki,S., Sakamoto, S. & Ide, Y. 1977. "A new
sweetpotato
variety "Minamiyutaka".
Bull. Kyushu Agr. Exp. Stn. 19 (2): 133-150(inJapanese)
Sakai, K. 1964. Studies on the enlargementof variations
and the improvement of selection
methods
in sweetpotato
breeding.
Bull Kyushu Agr. Exp. Stn. 9 (3): 247-397(in Japanese)
Sakai, K. 1965. Present and future of breeding the sweetpotato
cultivars with high yielding
and high
starch content. Agr. Tech. 20: 124-128
Sakai, K., Marumine, S., Horosaki, S., Kikukawa, S., Ide, Y. & Shirasaka, S. 1967. On the new

143variety of sweetpotato"Koganesengan". Bull. Kyushu Agr. Exp. Stn. 13 (1,2): 55-68 (inJapanese)
Sakai, K. 1989. Sweetpotato
breeding:
Its history
and direction.
Agr. Res. 2: 29-42 (in Japanese)
Sakamoto, S. 1970. Utilizationof related species on breeding of sweetpotato
in Japan. JARQ 5: 1-4
Sakamoto, S., Marumine, S., Ide, Y., Yamakawa, O., Kukimura, H., Yoshida, T. & Tabuchi, S. 1987.
"Benihayato":
A new sweetpotato cultivar registered.
Kyushu Agr. Exp. Stn. 24 (3): 255-277(in Japanese)
Sakamoto, S., Marumine, S., Ide, Y., Yamakawa, O., Kukimura, H., Yoshida, T. & Tabuchi, S. 1987.
"Shiroyutaka":
A new sweetpotato cultivar registered.
Bull. Kyushu Natl. Agr. Exp. Stn. 24(3): 279-305(in Japanese)
Shiga, T. 1984. New method of sweetpotato breeding using polycrossand parental line selection.
Ann.
Report of Natl. Agr. Res. Cent. 1: 84-89 (in Japanese)
Shikata, S. 1976. Breedingof sweetpotato
adapted to direct planting
and method of direct planting
culture. JARQ. 10: 174-177
Shikata,S. 1980. Utilizationof random mating populationsin sweetpotato
breeding.
Bull. Chugoku
Natl. Agr. Exp. Stn. (A) 28:1-48
Tarumoto, I., Shiga., Sakamoto, S., Ishikawa, H., Kato, S., Takemata, T. & Umemura, M. 1989. New
sweetpotato
cultivar "Hi-starch".
Bull. Natl. Agr. Res. Cent. 15: 15-29 (in Japanese)
Yamakawa, O. & Ono, T. 1977. The effect of inbreedingon the parental ability in sweetpotato
breeding.
Japan J. Breed. 27 (Abs.2):
236-237 (in Japanese)
Yamakawa, O. and Sakamoto, S. 1978. Studies on use of interspecifichybridbetween Ipomoea
batatas and /. trifida. Japan J. Breed. 27 (Abs.2):
6-7 (in Japanese)
Yamakawa, O. & Sakamoto, S. 1980. Studies on breeding sweetpotato
varieties
to true seed planting.
I. Flowering habit, seed-setting
and adaptabilityof natural flowering population
to true seedplanting.
Japan J. Breed. 30: 151-160(in Japanese)
Yamakawa, O. & Sakamoto, S.I987. Response to selectionof natural flowering
populationforadaptability
to true seed planting in sweetpotato.
Japan J. Breed. 37: 66-74 (in Japanese)
Yoshida, T. 1985. Inbreeding
coefficientsof breedinglines in sweetpotato.
Japan J. Breed. 35:
464-468 (in Japanese)
Yoshida, T. 1986. Inbreeding
coefficientsand yield in sweetpotato.
Japan J. Breed. 36: 409-415(inJapanese)
Yunoue, T. 1967. The fifteen year's history of agriculturalresearch in Kyushu. Kyushu Agr. Exp. Stn.
Japan. 153-156(in Japanese)Sweetpotato Cultivars
Content in JapanSHINJIRO

Bred for High Yield

and High Starch

KATO1

Introduction
Breeding sweetpotatoes
for high yield and high starch content has been
conducted at National Agriculture
Research Center in Japan. This program started
in 1967 by selecting
germplasm for use as parental lines. The parental lines arecharacterizedby high starch content and multiple
disease resistance,
and thesecharacteristics
have an additive
gene effect.
After selectionof parental lines,
general and specificcombining ability
are examined. Three cultivars have beensuccessfully
developed during the last decade.
The cultivar'Shirosatsuma''Shirosatsuma'
was registered as Norin 39 in 1986. It was selected at the
National Agriculture
Research Center (NARC) from a cross made in 1977 between
CS69136-2
and Tamayutaka. The female parent, CS69136-2
selected as a parentalline at NARC, is characterized
by the high starch content and multiple
diseaseresistance.
The male parent, Tamayutaka was bred as a new variety for industrial
use at NARC in 1960, is characterizedby high yield, good storability
and medium
starch content.
The main characteristicsof Shirosatsuma1 are as follows:
1) The color of the uppermost expanded leaf is light brown, other leaves are darkgreen and the leaves heart shapeed with many small lobes at the leaf edge. The
stem and internodes are green. The skin color of the tuberous root is lightyellowish
white, flesh color is white and the root shape is short, fusiform andlarge.
2) The sprouting ability is excellent.
Compared with the leading variety
fKoganesenganT the tuberous root enlarge later. The roots store well.
3) The starch content was equivalent to fKoganesenganf. Tuberous roots yield was
17% higher, and crude starch yield was 18% higher than fKoganesenganf in
Oosumi branch of Kagoshima Agricultural
Experiment Station.
1 Japan International
Tsukuba, Ibaraki

Center for Agricultural
305, Japan

Sciences,1464) 'Shirosatsuma'
is resistantto root knot nematode and black rot, and moderately
resistant to soil rot and root lesion nematode. However it is susceptible
to stemrot.
The cultivar

fHi-starchf'Hi-starch'
was registeredas Norin 41 in 1988. 'Hi-starch'
was selected at
NARC from a cross made in 1978 between CS7279-19G
and CS69136-33.
Bothparents, selected
as parental
lines at NARC, are characterizedby high starchcontent.
The main characteristics
of fHi-starchf are as follows:
1) The color of the uppermost expanded leaf is light green and other leaves aregreen and have a shallow single incision.
The stem and internodes are green.
The tuberous root is long and has pinky-lightbrown skin color. The flesh colorof the root is light yellowish
white.
2) The sprouting ability is moderately
low. Compared with fKoganesenganf tubers
enlarge a bit earlier.
The roots have poor storage ability
as those of'Koganesengan'.
3) The starch content is extremely high, approximately
30%, whereas'Koganesengan' has about 25%. The starch yield was 12% higher inperformance trials compared with 'Koganesengan' in Oosumi branch of
Kagoshima Agricultural
Experiment Station.
4) Whitenessand stickinessof starch and frequency distributionof starch grains
appeared to be improved, and the components of starch quality were lessinfluenced by culture conditions
compared with 'Koganesengan'.
5) 'Hi-starch'is resistant to root knot nematode, and moderately resistant to stem
rot and soil rot. It is susceptible
to black rot and root lesion nematode.
The new cultivar

Kanto 106f

'Kanto 106' will be registeredas Norin No. in 1994.
It was selected at
NARC from a cross made 1986 between Koganesengan and Hi-starch.
The female
parent,Koganesengan bred at Kyushu Agricultural
Experiment Station,ischaracterized
by the high yield and high starch content. The male parent, Hi-starchbred as a variety for starch production
at NARC in 1988, is a cultivar characterized
by the very high starch content.
The main characteristics
of 'Kanto 106' are as follows:
1) The color of the uppermost expanded leaf is green and other leaves are green
and have a shallow single incision.
The color of the stem and internodes isgreen. The flesh color of the root is yellowish
white. The tuberous root is longspindle and has yellowish
white skin color.

Fig.lThe

pedigree

chart

of

the

parental

lines

of

CS69136-2

andCS69136-33.

Fig.2The

pedigree

chart

of

the

parental

lines

of

CS7279-19G..

1492) The sprouting ability is intermediately.
Tuberous habit is of the moderately
earlier enlarging type compared with that of Koganesenganf. The roots show low
storage ability as those of Koganesengan\
3) The starch content of 'Kanto 106 was higher than 'Koganesengan',
and as highas 'Hi-starch'.
The crude starch yield was 23% higher than 'Koganesengan' in
performance trials at Oosumi branch of Kagoshima Agricultural
Experiment
Station.
4) Kanto 106f is moderately
resistant to stem rot 5 starch content of tuberous rootin grafts.
When Hi-starch was used as a grafting stock, regardless of scion, the starchcontent was higher than those of other grafts. When Koganesengan was used as
stocks, the starch content was second highest.
In the case of Okinawa 100 stocks,
the value was lower than those of other grafts, regardlessof scion type.
Consequently
it is believed that the high starch content of Hi-starch was controlled
by stock characteristics.
Similarly
dry root weight of Hi-starch stock grafts werehigher than other stock grafts, regardless of scion type. From the graft experiment,
root yield and starch content are believed to be affected by sink more than source.

Table

1 Starch

content(%)

ingraftedsweetpotato.

ScionsStockså -Hi-starch

Koganesengan

Tsurusengan

Norin No. l Tamayutaka

Okinawa No. 100 mean s.d.

H i‑s ta r c h

24 .6

2 1. 5

2 4 .82a 4

22 . 12 3 .021 2

1.3

K o g an es e ng an

18 .9

1 8. 620 .0

1 7. 7

20 .7

18 .5

1 9. 1

1. 1

Ts u ru se n ga n

16 . 6

1 5. 619 .6

1 5. 6

15 . 119 . 01 6. 9

1. 9

No r in N o . 1

17 .4

15. 8

16 .4

15. 3

16 . 315 . 3

1 6. 1

0.8

T a m ay ut a ka

15 . 716. 8

16 . 815. 816 . 014 . 2

1 5. 9

1. 0

Ok ina wa No . 10 0

13 . 212. 9

13 . 812. 5

13 . 7

13 . 3

1 3. 20.5

Me a n17 . 816. 918 . 616. 7

17 . 317 . 2

1 7. 4

s .d

3.8

2 .9

3.8

a 7

3.3

3.6

150

Fig.

Inheritance3 Frequency
distributions
for starch content in each of Fi population.
note)
i : Starchcontent of Hi-starch,
T : Starch content of the otherm.=ma1ef.=fema1e

mode of starchcontents

parent.

In order to improve the starch content (SC) efficiently,
it is importanttoknow its mode of inheritance,
particularly
when using varieties recently improvedfor high SC and yield. Crosses were made between Hi-starch (the common parent)
and other cultivars.
In the cross between Hi-starch(very high SC) andKoganesengan (high SC), overdominance was observed in the both directions
andthe SC values exceeded that of the parents, and SC showed a normal distribution.
In crosses between Hi-starch and Minamiyutaka (high SC) overdominance wasobserved in one direction.
SC values of the lower SC parent of Minamiyutaka wasexceeded, and the distribution
was also normal. In the crosses between Hi-starchand Tamayutaka (low SC) and between Hi-starch and Okinawa 100 (very low SC),
overdominance was observed in one direction with the SC values of the progeny
exceeding only the lower SC parents, Tamayutaka and Okinawa 100, and the
distribution
was normal. However, the segregatedindividuals
having the highest
SC value in the Fx generation
did not reach the SC values of the higher crossparent,Hi-starch.
From the above results of frequency distribution
and the directionof overdominance, it is consideredthat the inheritanceof starch content in the151

above combinationsof sweetpotato
cultivars
is controlled
mainly by additive
polygenic effects and partly by the dominant effects inducing the lower values ofthe starch contents.
Under the above inheritancemode of the starch content
mentioned, it is suggested that both of parents should have high starch content inorder to breed varieties with high starch content.
References
Sakamoto,

S., T. Shiga, H. Ishikawa,S. Kato, T. Takemata, M. Umehara and T.Ando, 1989. New
sweet potato cultivar"Shirosatsuma",
Bull. Natl. Agric. Res. Cent., 15:1-13(in Japanese)
Tarumoto, L, T. Shiga, T. Sakamoto, H. Ishikawa, S. Kato, T. Takemata, M. Umemura, 1989. New
sweet potato cultivar"Hi-starch",
Bull. Natl. Agric. Res. Cent., 15:15-29(in Japanese)
Tarumoto, I., H. Ishikawa, S. Kato, 1990. Inheritancemode of starch contents in Ipomoea batatas.
Newsl. Natl. Agric. Res. Cent. 7:7-ll

153

Questionsand Answers in Session

3

H.Takagi(Q):
Dr. Bacusmo, you mentioned sweetpotato tends to have profuse
flowering in the Philippines.
When you keep your germplasm collectionsin the field at the same place over several years, do you have any problems
with voluntary seedlings?
J.L.Bacusmo(A):We periodicallyclean and replant
plot. In this way we eliminate "volunteers".

partsof the 1 meter square

M.Djazuli(Q):Do you have any advice regarding keeping vines alive duringexploration?
Sometimes during a collecting
trip it is necessary to keepmaterial alive for a month or more.
J.L.Bacusmo(A):In the tropics when you put a large number of cuttings in abundle rotting can occur in the middle of the bundle and if not bundled theytend to dry up. In our experience wrapping the bottom portion of the
cuttings with moistened newspaper will allow us to keep the cuttings fromdehydration
and rotting for 2 weeks.

I.Tarumoto)Q):
In your presentation,
Dr. Bacusmo, you mentioned that yield
the primary objective.
Do you have any special reason for this?

was

XL. Bacusmo(A):In the Philippines
consumers and farmers have a range ofrequirements.
Some consumers eat sweetpotato as a snack food whileothers eat sweetpotato because they have no other choice. Some farmers
grow sweetpotato for the market while some grow it as a security crop.
Due to this diversityof needs we choose to focus firstly on breeding for
improved yield since this is the major criteria farmers use for chooseing avariety. This does not mean that quality improvement is not also important
it must also accompany yield improvement.
LShiotani(Q):
Dr. Bacusmo you used the wild species
this species have traits beneficial
to sweetpotato,
resistance?

Ipomea pescaprae. Doesfor example weevil

J.L.Bacusmo(A):Wewould like to think there are beneficial
genes in I. pescaprae
such as weevil resistance.
In one meeting however Dr. Talekar of AVRDC
showed a pictureof sweetpotato
weevil infestingstems of Ipomea

154

pescaprae. I. pescaprae, however, may have genes for tolerance
as it naturally
grows on the coast line in the Philippines.

to salinity

S.C.Halus(Q):Given the large number of accessions of sweetpotato availableinvarious collections
and the trend towards breeding for specific biochemical
traits, is there any effort to develop more rapid and reliable methods suchas in vitro or combined in vffro/biochemical
tests?
K.Komaki(A):We have no specific techniquesto evaluate specific biochemical
traits in vitro. However, we have just started to evaluate the resistanceofsweetpotato to Fusarium wilt in vitro. Hopefully
we will get some goodresults from this experiment.

M.Oka(Q):Is there any possibility
sweetpotato
breeding?

to use the tetraploid

breeding

materialfor your

K.Komaki(A):The yield of the tetraploid
sweetpotato
is high, but the starchcontent is lower than hexaploid
sweetpotato cultivars.
In addition,
it seems
that tetraploid
sweetpotato
is susceptible
to virus diseases.
Thus, thepossibility
for breeding with these materials is not high.
M.Mori(Q):In potato, some high pigmented lines have poor or somewhat bitter
taste dependingon the line. Is the taste of sweetpotato
also affected byhigh concentrationof anthocyanin.
Does anthocyanin affect discoloration
after cooking.
K.Komaki(A):Lines containing
much anthocyanin
usuallytaste bitterinsweetpotato
too. Anthocyanin
is an end product of polyphenol
synthesis
and polyphenol
sometimes acts as a substance inducing bitterness.
I think
that polyphenol
might affect the taste in high anthocyanin
cultivars.
Blackening
after cooking is not related to the taste.

H.Tauagi(Q):Non-sweet sweetpotato
varieties
could attract theinterestofbreeders in the tropics.
IVe heard that low B-amylase is a recessive
character. Since sweetpotato is hexaploid.
I think enormous effort should
be made to select for this trait.
Could you tell us how you could
incorporate selection for this trait in your breeding program?
O.Yamakawa(A):In the cross between non-sweet and sweet types of sweetpotato,
there is the chance of getting a small percentage of nonsweet lines. The

155

number is not so small as to discourage
non-sweet cultivars.

breeders

from developing

K.Okuno(Q):You mentioned B-amylase free cultivars developed in your program.
Is there any relationshipbetween B-amylase activity and longevityof theroots in storage?
(XYamakawa(A):Until now we have not found any relationship.
There will besome relationshipbetween storage ability and A-amylase which tends toincrease during storage.
V.Ramanatha Rao(Q): What is the significanceof maltose content in sweetpotato
breeding?
How long can the tubers of sweetpotato be stored at 13°C?
O,Yamakawa(A):We are trying to use sweetpotato in cooking in a similar way topotato which has no maltose after steaming.
In Japan we can store
sweetpotato in the store house from November to the next April at atemperature of between 13 and 15°C.
Y.Takahata(Q):content?
S.Kato(A):What is the chance of producing

a new line with higher

starchThe starch content of Hi-starch was reported as 32.5% at Shizuoka
Agriculture
Experiment Station.
However we think there may have been
an error in measuring the starch content because we have only obtained
30% starch content for Hi-starch.
Breeding is only likely to increase thisslightlyin the future.

T.Masuda(Q):To achieve high yield and high starch content in sweetpotato, whichis the dominant controlling
factor the abilityof the source or the sink?
S.Kato(A):In grafting of sweetpotato
with small and large sized tuber cultivars,
regardlessof scion type, photosynthatetranslocatedtowards large tubers.
So I believe yield is controlled
by the sink. Starch content will becontrolled
by enzyme activity of the sink.

LShiotani(Q):How were you able to breed a high yielding
even though it has a low yield?

varietyusing Hi-Starch

1Z£

S.Kato(A):Both parents had high starch content (23-25%)
and low yield. These
characteristics
acted additively.
Hi-starch did not have a very high yield.
From the cross Koganesengan and Hi-starch we bred Kanto 106 which has
a very high starch content and high yield.

TECHNICAL

Session

REPORTS

4

TARO AND OTHER ROOT CROPS

ChairmenKazuo Kawano
Kenji Takayanagi

Taro Genetic

Resources and Utilizationin Indonesia

MUHAMAD DJAZULI1

Abstract
Taro (Colocasia
esculenta (L) Schott) is the third most important root crop in Indonesia,
after cassava and sweetpotato and it originatedin Southeast Asia probably Indonesia.
17 accessionsof taro were collected
in 1931 from East and Central Java. In the Molluccas 12 accessions arecultivated by fanners, while 4 accessions collected are maintained in in vitro culture. 143 accessions
were found in Irian Jaya. At BORIF-CRIFC,
19 accessions
from Java are maintained in the
germplasm collection.
Some accessions have been characterized
for pre- and post-harvest
traits.
Recently, 87 accessions were collected on Mentawai island, West Sumatra. Yields of taro range from
6 to 10 t/ha. Taro is cultivatedin the lowlands and highlands
up to 2.700 m above sea level. Tarois consumed as a staple food in Irian Jaya, the Molluccas, and Mentawai island, West Sumatra. In
Java, corms are consumed as chips and steamed corm, while leafy parts are used as vegetables.
Recently, taro is thought to have good prospects as an agro-industrial
crop in Indonesia.

Introduction
Food diversification
has high priority
in the agriculturaldevelopmentofIndonesia in order to sustain food self-sufficiency
which was achieved in 1984.
Increasing populationand limited suitable agriculturalland has caused farmers tomove onto marginal soils with many unfavorable conditions.
Taro or cocoyam (Colocasia
esculenta(L) Schott)is the third mostimportant root crop in Indonesia after cassava and sweetpotato.
As a minor foodcrops, however, taro received
littleattention
both from policy makers andresearchers.
Taro grows best in fertile, heavy and moist soils, however, some cultivars
are also tolerant to upland conditions.
Currently,
no exact estimatesof the harvested
area, productivity,
andcultivarsof taro in Indonesia are available.
Therefore, systematic
explorationona national scale should be done.
As native crop, taro grows in all parts of theIndonesian archipelago
from lowlands to highlands
and has various uses.
History
Taro is found wild from India to Southeast Asia, and has spread throughout
the tropical world up to the border of the temperate zone. Toward the east the

Bogor Research Institute
Bogor, Indonesia

for Food Crops,

160

plant was spread by Malaysiansor Polynesians
to all the islands of Oceania,
including
Hawaii and New Zealand. Taro reached China in about 100 BC. The
spread of taro to the west is poorly documented. From Southeast Asia, taro was
brought to African by Indians or Indonesiansaround 500 AD (Mauny, 1953 inLeon, 1976).
Colocasia esculenta has been cultivatedfor a long time and is distributed
across the islands of Indonesia.
In western part of Indonesia,
except Mentawai
island, taro is used as a supplementary
food, while in the eastern parts, it is used
as a staple food together with sweetpotato,sago, and cassava.
Botanyand Cultivation

SystemTaro {Colocasia
esculenta (L.) Schott)belongs to the genus Colocasia,
within the monocotyledonous
family Araceae. This crop is classified
into twogroups: the dasheen type {Colocasia
esculenta (L.) Schott var. esculenta)
which ischaracterized
by larger conn and small cormels and the eddoe type {Colocasia
esculenta (L.) Schott var. antiquorum) which is characterized
by larger cormels andsmall corm. In Indonesia, the dasheen type is more commonthan the eddoe type.
Taro grows best in wet heavy soil with good fertility,
adequate humus, and gooddrainage.
Most farmers in Indonesia
use lateralbud seedlings
as a planting
material. They plant with varying spacing between plants.
Plant spacing for thelarge cultivars ranges from 100 x 60 to 150 x 60 cm, while for small cultivars,
itranges from 30 x 45 to 75 x 50 cm (Danimihardja,
1978).
Crop duration of tarovaries from 5 to 12 months, and it is influenced by genetics and environmental
conditions,especiallytemperature.
In Bogor, growing period of taro is between 6
and 9 months.
Productivityof taro varies among accessions and growing conditions.
It
was reported that average yield of taro in the Biak regency, Irian Jaya is 10.3 ton/ha(Anon., 1990),
while the productivityof taro in the highlandsof Irian Jaya
generally,is much lower due to low temperature and soil fertility.
In Bogor, as a
production center, taro yields range from 500 to 3000 g/pl. Informationof harvested
area of taro is limited, however, it was reported that three production centers of taro
Biak Rumfor, Bogor, and Mentawai have a harvested area are 573, 115, and 50 ha,
respectively.
As a minor of food crops, taro has received little attention
both fromdecisionmakers and researchers.
Only germplasm exploration
and agronomic
studies have been conducted. Taro is very susceptible
to leaf blight disease causedby the fungus Phytophthora
colocasiae. It was reported that of 10 cultivars tested,
all were affected when inoculated with taro leaf blight.
This fungus was able toreduce yield by up to 54 % (Soenarto and Tethoal, 1976), and up to 80 % in two
locationsin Irian Jaya.
It was also reported that epidemicsof taro leaf blightdisease occurred twice in Irian Jaya, the first one occurred in Sorong regency in1976 (Soenarto
and Tethoal, 1976), and the second in Biak island during 1981

16

Figure1. Taro production

centers

in Indonesia(Patiasina

et al, 1981).
Taro is usually intercropped
with other root crops, such as sweet potato in
Irian Jaya, it is also a well established
as a crop bordering wet rice fields in many
agricultural
systems.

Distribution
As a native crops of Indonesia,
taro is widespreadon many islands inIndonesia from Sumatra to Irian Jaya (Western part of Papua) (Fig. 1). Up to thepresent no systematic explorationof taro was conducted in most production centers
in Indonesia.
The first taro explorationin Indonesia was made by Osche in 1931.
He reported on the use and cultivationof 17 accessions collectedfrom East andCentral Java (Danimihardja,
1978).
The diversityof taro in Irian Jaya is relatively
high. From some exploration
conducted by Cendrawasih University
teams, they have found 64 accessions inSorong regency (Patiasina
and Paiki, 1981)
and 27 accessions in Manokwari
regency (La Achmady, 1983). Matanubun et al (1991)
reported that the Center ofRoot and Tuber Crops Studies (CRTCS)-Cendrawasih
University
explored thePaniai regency, Irian Jaya, and collected 52 accessions of taro from the three sites(Table 1). In Jayawijaya
regency, Irian Jaya it was estimated that more than 20
cultivars of taro grew in the area. Even taro was found at Kuyawage district,
Irian
Jaya, at an altitude more than 2.700 m see above level and at least five varietiesoftaro are cultivated.
In Irian Jaya the germplasm collectionof taro is maintained
both in the
farmers field (in situ) and in the experimental
field of CRTCS-Cendrawasih

162

Table

University

1. Listof taro accessions
Province, 1990

collected

in Paniai

Regency,

Irian Jaya

(ex situ).
An explorationteam from Pattimura University,
Ambon reported that in
Molluccas islands at least 12 varieties
were cultivatedby farmers, and 4 cultivars
among them were maintained by Pattimura University,
Ambon in in vitro culture(Table 2).
Recently,
87 accessionsof taro were found in Mentawai island, West
Sumatra by a team from Sukarami
Research
Institutefor Food Crops(SARIF- CRIFC).
As a research institute,Bogor Research Institutefor Food Crops (BORIF)
has characterized
19 accessions of taro collectedfrom East Java, Central Java, andYogyakarta provinces (Kartowinoto
and Ngatimin,
1993).
Two accessions among

163

Table

2.

List of taro accessions
East Java, and Central

collected in Yogyakarta,
Java provinces

West Java,YL=Young leaf;
OL= Old leaf;
VN =Vein;
PT= Petiole
g=green;dg =darkgreen;
p=purple;w=whiteEddoe type with larger

cormels and small corm.

Table 3. List of taro accessions
at Patimura University,

collected
Ambon

in the Molluccas

them belong to the eddoe type with larger cormels and small corm (Table 3).
Names of cultivars are usually based on morphologicalcharacteristics,
taste,
color, or origin.
For instance, Talas Sutera means Taro (Talas) with fine hair, or
silky skin (Sutera).
Talas Ketan means taro with a taste like sticky rice (Ketan).
Talas Bogor means taro originatingfrom Bogor (Table 3).
Use and Future Prospect

protein,of Taro in Indonesia

Both upper and underground part of taro have relatively
good carbohydrate,fat, and mineral content (Table 4). Protein content of leaf is much higher

164

Table 4. The approximate,taro corm

nutrientand vitamincompositionof fresh

1. Payne, et al 1941. In Danumihardja,
1978.
2. Murai et al, 1956 In Plucknett,
1976.
3. Anon. 1989.

than that of corm parts both in wild and edible varieties(Danimihardja
andSastrapradja,
1978).
Taroand potato have a higher alkalinity
than cerealia(Watt andBreyer-Brandwijk,
1962). Furthermore, he reported that the people who consumed
taro have better and stronger teeth than those of consume sago as a staple food.
In Indonesia,
taro is consumed both as a supplementary
food and staple
foods. In Java, with the highest population,
various additional
foods are made fromtaro such as chips, fried or steamed corms, and for other traditional
snack foods.
In the production
center of Bogor farmers and small retailers sell fresh taro aroundthe famous Botanical Garden and other tourist destinations.
Accordingly,
taro isbecome a characteristic
souvenir food from Bogor.
Taro leaf and petiole are used as a vegetable.
Taro is also used as a
traditional
medicine.
Winarno (1990) reported that root extract can be used as a
medicine for rheumatism and acne. While extract of leaf can be used for clotting
blood, neutralizing
snake poison, and as a purgative medicine.
Cultivationof taro close to urban market is more profitable.
It wasreported that R/C ratio and the net income per capita of taro farmers in Bogor was
significantly
higher than that from other food crops (Table 5).
The comparativeadvantage of Taro is its low production cost, and a relatively
high price.
To increase demand for taro, a diversityof taro products
should be
developed.
Various foods using taro flour have been developed in order to reducethe demand for imported wheat flour.
It was reported that Bogor Agricultural
University
and BORIF succeeded in producing various processing products from

165

Table

5.

Analysis of farming
1990-1991

system of several

food crops in Bogor,

19 9 019 9 1

C o m m o d ity

F a r m (Re rps .0in 0c 0o )m e l R / C 2

F a r( mR pe r s.0 0in0 c) o m e

T aro
R ic eM a iz e
C as sav a
S w e e tp o ta to
P ea n u t
S o y b e an
M u n gb ea n

2 .6 7 8
1 .1 2 0
676
829
704
894
578
399

2 .6 1 7
1 .3 7 9583
1 .1 7 6
1 .1 9 4
1 .4 8 3607
470

2 .4 0
1 .8 7
1 .4 4
1 .6 6
1 .7 2
1 .9 7
1 .5 0
1 .4 7

R /C

2 .5 0
1 .9 91 .6 0
1 .9 42 .1 0
1 .9 0
1 .3 0
1 .3 2

1 Production value (including
rental land and labour cost)
total production cost
2 Production value/total
production
cost

taro such as starch, flour, glucose syrup, cake, and biscuits.
Increasing populationin Mentawai island, West Sumatra, the Molluccas
Irian Jaya which consume taro as a staple food, improving
productivity,
increasing planting area should be seen as a priority activity.

and
and

Conclusion
As a native crops, taro is widespreadin Indonesia.
In 1931, explorationoftaro in Indonesia
was pioneered.
However, information
on genetic resources,
production,
harvested area, and use of taro in the national research system is still
limited.
About 17 taro accessions from East and Central Java, 12 accessions from
Molluccas islands, 143 accessions from Irian Jaya, and 87 accession from Mentawai
island,West Sumatra have been collected
and are maintained
as a germplasm
collection.
Phytophthora
colocasiae is still a main constraint in production.
Taro has a relatively
good nutritional
value, and various taro products havebeen developed as supplementary
foods. While in the eastern parts of Indonesia
especially
the Molluccas and Irian Jaya, and Mentawai island, West Sumatra, taro
is consumed as a staple food.
Taro has a good prospect as a cash crop in urban areas and as an industrial
crop in the future.
Acknowledgements
The author wishes to acknowledge the financial
support of the NIAR,
Japan, and the help of Dr. A. Dimyati, Dr. M. Yusuf, and Mr. S. Kartowinoto of
CRIFC, Mr. F.A. Paiki of Cendrawasih University,and Dr. Jurg Schneider of

166

CIP-ESEAP

regional.

References
Anonymous 1989. Compositionof food material list. Brathara. Jakarta.
Anonym. 1990. Biak Rumfor on statistics.
Statistical
office. Biak Rumfor.
Danimihardja,
S. 1978. Utilizationand cultivationof Talas (Colocasia
esculenta (L.) Schott).
Bulletinof Botanical
Gardens. Vol 3. No. 4. pp 101-107.
Kartowinoto,
S. and Ngatimin. 1993. Rejuvenationand characterizationof Minor root crops
germplasm. Progress Report. BORIF, Bogor. 12p.
La Ahmady, 1983. Evaluationof Colocasia
sp, Xanthosoma sp, and Alocasia sp germplasm in
Manokwari. Fac of agriculture,
Cendrawasih University.
Manokwari.
Lalopoa, J.R., R.E Wattimena, A. Walsen., and S.H.T. Rahardjo. 1989. Proc. Seminar on Developmentof tuber crops potential.
Fac. Agriculture,
Pattimura University-USAID.
95-130
Leon. J. 1976. Origin, evolution,and early dispersalof root and tuber crops. Pages 20-36 Proc.
fourth Symp. Inter. Soc. Trop. Root Crops. Cali, Colombia.
Matanubun, H, J. Renwarin, F.A. Paiki, Gunaryo, A. Rochani, and H.T. Dedaida. 1991. First
Explorationof root and tuber crops in Paniai and Biak Rumfor regencies, Irian Jaya. Centerof Root and Tuber Crops Studies,
Cendrawasih
University.
Manokwari. 47p.
Onwueme,I. C. 1979. The tropicaltuber crops ; Yam, Cassava, Sweetpotato,
Cocoyam. John Wiley,& Sons, pp 199-267
Patiasina,
J.W. and F.A. Paiki, 1981. Explorationof taro and tannia in Ayamaru. Fac. of Agriculture,
Cendrawasih University.
Manokwari.
Patiasina,
J.W., J.P. Karafir, AM. Killian, and F.A. Paiki, 1981. Preliminary
study on disease controlof taro leaf blight in Irian Jaya. Fac. of Agriculture,
Cendrawasih University.
Manokwari.
Plucknett,
D.L. 1976. Giant Swamp Taro, a little known Asia- Pasific food crop. Pages 36-40. Proc.
fourth Symp. ISTRIC. Cali, Colombia.
Purseglove,
J. W. 1981. Tropical crops : Monocotyledons.
Longmans. 5th edition.
Purwanti, H. 1986. Resistanceof Taro (Colocasia
esculenta)
accessions
to Bacterial
Leaf Blight(Phytophthora
colocasiae).
Agriculturalresearch. Vol 4:5-7
Soenarto and Y.Tethoal. 1976. Study on epidemic taro disease at Ayamaru district.
LPPPM.
Manokwari.
Tindall.
H.D., 1983. Vegetablesin the Tropics. MacMillan Press. London, pp 52-56
Watt, J.M. and M.C. Breyer-Branwijk.
1962. TTie medicinaland poisonous plant of southern andeastern Africa. E&S Livingstone,
London. 1457 p.
Winarno, F.G. 1990. Food chemistry.
Bogor Agricultural
University.
Bogor.

Root and Tuber Crop Genetic

Resources in Vietnam

TRUONG VAN HO AND COLLABORATORS1Introduction
Vietnam is rich in Plant genetic Resources, root crops in particular.
Rootcrops play an important role as human food, animal feed, medicines, spices anddyes.
Civil and political
disturbancesin Vietnam have been major factors
contributing
to genetic erosion of crops (Table 1). The collection
and conservationof root crop genetic resources therefore is becoming increasingly
urgent.
The Potato and Vegetable research Center (PVRC) of the National Instituteof Agricultural
Sciences (INSA) is responsible
for the National
Root and Tuber
Crops Project.
This project receives financial
support from the International
development research Center (IDRC),
Canada, and the technicaladvance of theInternational
Potato Center (CIP).
It is conductedin collaboration
with many
institutions
in Vietnam and aims to collect, maintain and evaluate root and tuber
crop germplasm.
This paper presents the findingsof and collecting
missions throughout
Vietnam during 1992-1993.
Lying between 8°N and 23°N and 102°E and 110°E Vietnam can bedivided into 8 agro-ecologicalregions. The average temperature ranges from 22°C
to 27°C. The temperature is lower in the north where the temperature is subtropicalwith cold winters. The annual rainfall in different
ecologicalregions varies from1500 mmto 2500 mm. The dry season lasts from November to April and the wet
season from May to October. Towards the east lies the sea and in the west theTruong Son mountain range. The terrain is highly varied and slopes down towards
the sea. Mountains and hills cover four-fifthsof the country. The cultivatedarea
Table 1.

Factors

affectinggenetic

erosion in Vietnam

Enlargement of farms and plantationsin the mountainous regions
Pressure from the increasing population
Replacement of indigenous varieties by modern cultivars
Changed cropping patterns
Spontaneous resettlement
and migration
Constructions
and development
30 years of war

National Instituteof Agricultural
Sciences
Van Dien, Thanh Tri, Hanoi, Vietnam(INSA),

168

covers 7 million ha including
4.3 million ha under rice, the rest is under uplandcrops and perennial plants. The variability
in climate, edaphic factors and diversity
in farming systems in Vietnam have generated different
types of genetic resources
for various crops. Collecting
root and tuber crops in Vietnam.
Based on their economic importance and scientificsignificance,root crops,
in order of priority to Vietnam, are:- sweetpotato, taro, yam, cassava, Canna andother minor root crops used as medicines, dyes and spices.
The main principles
of exploration and collecting were applied based on thecrop genetic resources field collecting
manual of Hawkes (1980) and the standard
passport descriptors
recommended by the International
Board for Plant Genetic
Resources (e.g. IBPGR, 1980; Huaman et al., 1977). Information on varieties andtheir localities
were obtained in the collecting
areas from farmers, villagers,
local
scientists
and cadres.
Culturalpracticesand production
constraints
were also
recorded.
During 1992 to 1993 the collecting
missions were organised as 10 trips
covering the main regions of the country. 100 field days of collecting
were carriedout in total. The total distance travelled was more than 10,000 km. Itineraries
ofthe collecting
missions are shown. The districts where collecting
was undertaken
is shown (Tables 2). A total of 1208 accessions were collected and of these 518
were sweetpotato, 402 taro, 69 yams, 128 cassava, 33 canna and 58 minor root andtuber crops (Table 3).
Diversity

observed

SweetpotatoIpomea batatas (L.) Poir
Sweet potato was introduced
to Vietnam centuries ago, and is widely
adapted to all agro-ecologicalregions.
Sweetpotato
ranks first among the root
crops of Vietnam in terms of growing area with about 400,000 ha and is grown inalmost all regions.
It is considereda crop of poor farmers because:
a: no other root crop can yield as well as sweetpotato
b: planting
and harvesting can be done at any time of the year
C: it does not require much investment unlike rice and maize
It is grown in rotation with rice and upland crops such as maize, beans andvegetables.
The most popular varieties, know to exist many decades ago are Lim,
Chiem dau, Choi sa, Bi etc. The species /. digitata,I. hederacea, I. maritina, I.
aquatica of the GENUS Ipomea were also collected.
But no wild species closely
related to the sweetpotato
has been found. A total of 518 accessions was collected
and are kept at the PVRC. A large amount variation was observed for the type ofvine, leaf size, leaf shape and color and storage root characters.

169

Table

2.

Table 3.

Collecting

sitesof root anf tuber crops

Root crops collectedin Vietnam during 1992-93

A.

170

Table 4.

Araceae accessions

B o ta n ic a l n a m e

Na coc e. so sfio n s

P art u se d

R em ark s

C o lo c a s ia s p .

290

pT eu tiob e ler , l e a f,

aH nuimm a ln foa nodd

X a n th o s o m a s p .

80

pT eu tiob e ler,

aH nuimm a ln foa nodd

A lo c a s ia m a c r o r r h iz a

15

pT eu tiob e ler,

Am ne di mi cainl ef o o d ,A m o rp h o p h a l lu s sp .

7

sT tua lk
b er,

maH nueimdm i ca inln efoa no dd ,T o talcollected

and their uses

402

Taro
Taro is used as a collective
word for general edible aroids- Alocassia,
C y r to s p e r m a cXanthosoma,
h a m is s o n is
4 but it Ais ll palso
a rt s appliedA n im toa l f oeachodColocasia, Cyrtosperma,of the aroids
S c h iz o c a s ia r e q n ie r i
3
A ll p a rt s
O rn a m e n t a lseparately.
ThereL a s iais spnoin o dataon
taro
growingarea
andproduction
buttaro
is grownsa1
T u b erM e d ic in e
in almost all regions
from 5T u mmany different
T y p h o n i u min d areas
iv a r i c a turangingm2
b e r to 1,800 M e dm
ic inandeagro-environmental
conditions.
Up to now no research on taro varietal
improvement or cultural practices
has been conducted in Vietnam (Table 4).
Among the species collected,
C. esculenta, C. antiquorum, X sagittifolium
andcampanulayus are grown as food crops. Son la, Ha bac and Quang ninh provinces
are the principal
provinces growing C. esculenta.
Other taro's are not used as
human food because they contain an irritating
agent of varying amounts in the leaf,
petioleor corm. This group can be grown under a wide range of hydrologicalregimes from flooded fields to rainfed upland conditions.
Wild relatives
occurredalong roadsides and forest margins, mostly in shaded area in Tuyen quang and Caobang provinces.
Some varieties
produce a large edible main corm with few
cormels; others produce a small or medium sized main corm that often may beinedible
because of the acridity
and a large number of small edible cormels. Widevariation with respect to shape and color of conns, leaf, plant height was observed.
Yam-Dioscorea alata, D. esculenta
A total collectionof 69 samples of both wild and cultivatedforms were
found distributed
throughout Vietnam (Table 5). Almost all are climbing plants andmost of them have thin stems, and storage organs under the soil surface.
D.
bulbifera
grows large tubers in the axils of leaves.
Phu tho and Tuyen quang
provinces have a considerable
area under D. esculenta cultivation.
While Quangninh, Ha bac provinces grow D. alata on a larger scale. In the south, D. alata is171

Table 5.

Yam species(Dioscoreasp.) collected

B o t a n ic a l n a m e

sN a mo . polef s

R em ark s

D . a la ta

47

Ttu hb ee rp rhina vceip ma la ny ay m fo sp
r m e cs ie s ,D . e s c u l e n ta

17

On on lyb ittf eo ru nf do rmin s c u lt iv a t io n ,D . b u l b if e r a
D . h isp id a

1
2

E d ib l e a e r ia l tu b e r s
Gin rsoewc tsic wid eil d a.n Ud sme de da ic
s in eT ota1

69

D . p e rs im il is2Imm e pd oicrtine de f o o d , tr a d it io n a lfound of economic importance in Long an and Tien giang provinces.
Apart fromthe two species mentioned above, there are a range of the useful Dioscorea species.
D. cirrhosa is used as a traditionaldye, D. perimilis is used as food and medicine,
D. hispida is used as a medicine.
The different
types of yams and their many
properties
are well known to local people.
Large amounts are gathered from their r h o s a2
D yewild when local DD .. flcdpeople
want
them.
DuringcollectingZ). floribunda
and D.
eo ltor ibidu en ad a1
In tr o d u c e d . M e d ic in a l p l a n t
deltoidea
were found which are thought to be new introductions.
Large variationin leaf shape, leaf lobe number, cross section of the stem, flash color and tuber
shape were observed. Farmers always name a yam according to the shape of the
tuber.

Cassava- Manihot esculenta Crantz
Cassava was introduced to Vietnam more than one century ago and became
an important source of human food all over the country, especiallyin the highlands.
Cassava is often grown on sloping and hilly land some of which have ben severely
eroded so the soil is very poor. But people continue to plant this crop because inhighly infertile
soils no other crop will grow. The area cultivatedto this crop isapproximately
350,000 ha with annual production of about 3 million tons of fleshlyroots. Production
is concentrated
in the northern mountainous region, the south
central coastal region and the southeasternregion.
At least 40 cultivars are believed to be planted throughout
the country ofwhich Canh nong in the north and Gon in the south are considered to be the oldest.
Two cultivars, Mi trang and Vinh phu are widely grown in nearly all cassava
producing regions.
In recent years, with the assistance of the International
Center for Tropical
Agriculture(CIAT)and other scientificinstitutions,the Hung Loc Agriculture
research center and Agricultural
instituteno 3 have undertaken cassava varietal

172

improvement with promising results.
The making of dry chips, starch (wet anddry), alcohol, maltose, noodles and cakes are long-standing
traditional
techniques
used by farmers in some locations, such as Hoa binh, Vinh phu, Ha tay, Thua thien,
Hue, Dong nai, and Kong turn.
EdibleCanna. Canna edulis Ker.
This species originates from South America where it is known as achira in
the Andes. The plant is a perennial and a robust herb. The rhizomes are large andup to 60 cm long, and much branched.
There is variationin the shape of therhizomes, as well as in the compositionof the rhizome. 6 groups of Canna can be
distinguished:
Tall plants with broad violet leaves
Tall plants with narrow violet leaves
Short plants with narrow violet leaves
Tall plants with broad green leaves
Tall plants with narrow green leaves
Short plants with narrow green leaves
A total of 33 accessions of Canna spp. have been collected.
Among them,
5 have beautiful
leaves and flowers and are used as ornamental plants and twovarieties
are used in traditional
medicine.
Edible Canna is grown on an estimated 30,000 ha, producing 300,000 tonsof fleshly rhizomes. A long duration crop, Canna is usually grown in monoculture,but sometimes it is mixed with other crops. Processing centers having noodles as
the main product are found in the large scale Canna growing areas of Hanoi, Hueand Dong nai provinces.
Other minor root and tuber crops - dyes, spices, medicinal plants.
Root and tuber crops as sources of dyes, spices or traditional
medicines arelisted (Table 6). Their distribution
is scattered in all regions.
Some varieties areplanted mainly in home gardens for home consumption. Some usually grow wild
and people gather them in the forest when needed. Some times they are very rare.
Most samples collected belong to the Zingiberaceae
family. It is difficult
to definewhich species should be included as spices or medicinal plants, but they are all
locally used as a source of dyes, spices or medicines.
Conclusions

and recommendations

This paper reports the first systematic collecting
missions concentratingonroot and tuber crops in Vietnam. Information on distribution,
diversityof natural
habitats
and genetic diversity was obtained.
The considerable
number of samples, collected indicates that rich diversityof root germplasm exists in Vietnam.
Some species belonging
to the Araceae,

IBPGR

173

Table

6.

Other

minor tuber crops in Vietnam

B o tan ica l n am e

Nsamo . polef s

U se

C u r cu m a lo n g a
C u r cu m a sp .
Z in g ib er offi cin a le
Z in g ib er je ru m b et
A lp in ia offi cin a r u m
A lp in ia g a la n g a
K a em p fer ia g a la ng a
K a em p feri a sp .
S tem o n ia tu b ero sa
M a r an ta a r un d in a c ea
P u era r ia th o m s o n i
P u era r ia sp .
S tep h a n ia ro tu n d a
P a c hy r rh izu s e ros us

4
3
12
4
9
3

d y ; sp ; m ed y ; sp ; m esp ; m e
sp ; m e
sp
sp

1

af

T otalNotes:

dy-dyes;

sp-spices;me-medicine;

af-animal

food

Zingiberaceae
and Dioscoreaceae are native to Vietnam.
More detailed explorationand collection
should be organised and aimed atparticularspecies in remote areas where variability
is known to exist.
References
Hawkes, J.G. 1980. Crop genetic resources field collection
manual. IBPGR/EUCARPIA
37pp.
Huaman, Z., J.T. Williams, W. Salhuana and L. Vicente. 1977. Descriptors
for the cultivatedpotato.
Rome, Italy 44 pp.
IBPGR. 1980. Descriptors
for yam (Dioscoreasp.) IBPGR, Rome, Italy.

CharacterizationJapan

and Phylogenyof Taro Genetic Resources in

HlRAI1 MASASHI

Introduction
Although wild taro(Colocasia
esculenta var. aquatilis)
is reported in the
Ryukyu islands of Japan, cultivatedtaro did not become domesticatedin Japan, andis believed
to have been introduced
to Japan from tropical areas through China.
The beginningof rice cultivation
has long been thought of as the beginningof
agriculture
itselfin Japan.
However, some Japanese anthropologists
recently
pointed out that taro has possibly
been cultivatedfrom late Jomon period(10thcentury B.C.), far before the beginningof rice cultivation(Sasaki1986).
Taro has always been a main crop in shifting
cultivationin Japan, and taro
is sometimes especially
important in local ceremonies. Therefore, knowledge of theorigin of taro cultivationand cultivars
are important to elucidate
the origin ofJapanese agriculture.
In Japan taro is not a staple food, but is used as a vegetable.
Cormels aremainly used for cooking, but sometimes petioles are used as vegetable.
Taro iscultivatedin upland fields on main islands of Japan, but in the Ryukyu islands,
some cultivars are cultivatedon pond fields.
Japan produces about 300,000
tons
per year, but the production
is now slightly
decreasing.
Taro Cultivars

in Japan

Kumazawa(1956)
recorded 194 cultivars,
al.(1989) groups. Analyzing 80 cultivars, Hirai et
Major groups are as follows:

and those were classified
reported 9 morphologicalinto 22groups.

Eguimo group: Triploid.
Distinct
in its deep green petioles.
Sprouts earlier thanother cultivars.
Cold-hardy.
Flowers under natural condition in Japan.
Produces many cormels having smooth flesh. Only cormels are used as food.
Main conns are slightly
acrid.

1 National

Research Instituteof Vegetables,

Kusawa, Anocho, Mie 514-23,

Japan

Ornamental

Plantsand Tea (NIVOT),

176

Ishikawa-wase group: Triploid.
Distinctin dark colored fringe of the petiole.
Produces many sphericalcormels. Cormels are smooth in texture and earlymaturing. Cultivatedin Osaka and neighbouring
areas of Japan. One of themost economicallyimportant groups.
Dodare group: Triploid.
Produces many cylindricalcormels having a smooth flesh.
Mainly cultivatedin the eastern region of Japan. One of the most importantgroups for taro production.
Hasubaimo group, which is distinct in its horizontally
lifted leaf laminae, may classified
in a sub-group of the Dodare group.
Akame group: Triploid.
Distinct in its reddish anthocyanin pigment in petioles
andbuds. Produces large sphericalcormels. Texture is intermediate.
Both corms
and cormels are used as food. Mainly cultivatedin Kyushu. Less cold-hardy
than the other triploid
cultivars.
Cultivars named "Serebesu" are classified
in thisgroup.
Tonoimo group: Diploid.
Petiolesare dark-purple
brown. Produces many
shrimp-shaped
cormels, when cultivatedwell. Sometimes produces slender
spindle-shaped
cormels, when poorly fertilized.
Flesh texture is hard andpowdery. Less cold hardy than most of triploids.
Cultivatedin Kyoto and thesurrounding areas and used for traditional
cooking in Kyoto. It is sometimes
named "Ebiimo".
Yatsugashiragroup: Diploid.
Many buds sprout from a single corm (Fig. 2), andthe corms grow into irregular shape. Cultivatedmainly for petiole productionasa vegetable.
Acridity in the petiole is low. The other characters are the same as
those of Tonoimo group.
Taimo group: Not yet characterized
in NIVOT. Produces large main corm and a
few cormels. Cultivatedon pond field in the Ryukyu islands south in Japan.
Main corms are boiled, mashed and used for traditional
cooking in the Ryukyu
islands. Possibly
related to cultivars on Lanyu Island, East of Taiwan Island.
The variationin corm protein

Analysing
80 cultivars
using
non-denatured
polyacrylamidegelelectrophoresis,
only 8 patterns were found in corm storage protein.
Three of the
8 were found in minor cultivars,
Binroshin,
Takenokoimo, and Migashiki(Hirai etal, 1989)(Fig.
1). Therefore most of the Japanese cultivars of taro were classified
into 5 protein patterns, which suggests very low genetic diversity.
In natural conditionsin Japan taro cannot produce seeds. Only cultivars
in the Eguimo group can flower under cultural conditions,but cannot produce seeds
because of low temperatures in autumn. These 5 groups may be of clonal origin.

77

FigureFigure1. Electrophoretic
pattern of corm protein.
C: Takenokoimo, B; Binroshin,
M: Migashiki,
T:Ebiimo(Tonoimogroup), A: Serebesu(Akame
group),
D: Dodare(Dodare
group), I:Ishikawa-wase-maru(Ishikawa-wase group), £:Eguimo(Eguimogroup)

2. Conns of Tonoimo(left)

and Yatsugashira(Right).

178

Within groups, minor differencesin color or shape were also recorded. Many local
cultivars may originate by mutation.
A total of 40 morphologicalcharacters were scored on the 80 cultivars.
A
dendrogram based on 40 morphologicalcharacters coincided well the results of theprotein analysis and horticulturalclassification(Kumazawa et al. 1956). The resultsof morphologicaland protein analyses lead to the following
hypotheseson theorigin of Japanese taro cultivars.
Ishikawa-wase was not recorded in the old literature,and is thought to haveoriginatedin Osaka prefecture in the 19th century.
This cultivar has the same
protein pattern as Kurojiku, an old cultivar recorded in the 18th century. Shoot tip
culture of Ishikawa-wasesometimes results in mutants having dark-coloredpetioles,which is common to Kurojiku.
These mutants are less productivethanIshikawa-wase.
Ishikawa-wase may have originatedfrom the Kurojiku group by
mutation, the mutant being selected and propagatedby farmers because of the
productivity
and earlier production of the tubers. The mutation during tissue culture
could be a back mutation.
Yatsugashirashowed a protein pattern common to that of Tonoimo.
Injectionof gibberellicacid to the meristem of Tonoimo sometimes resulted in achange in growth habit as seen in Yatsugashira.
Gibberellicacid may activate
lateral meristems, and the resulting
growth of many petioles.
These findings
suggest that Yatsugashiraoriginatedfrom Tonoimo by mutation, and the mutation
includes the change in hormonal metabolism (Fig. 2).
DNA analysis
The spacer region of ribosomal DNA is reported highly to be variable, andhas been*used to understand genetic relationshipsof species and cultivars.
A spacer
fragment of taro cloned by Dr. P.Matthews was used to elucidate the relationships
between taro cultivars.
Taro total DNA was digested with Taq I, separated byelectrophoresis,
blotted to a membrane and probed with the spacer fragment. A 2.8
kb fragment, which has been found in wild diploidtaro in Queensland,
Australia(P. Matthews, 1990), was also found in Japanese diploid
cultivars.
The samefragment was also found in wild taro (var. aquatilis)
in Okinawa (Fig. 4 and 5).
While major triploid
cultivars in Japan, Eguimo, Dodare, and Ishikawa-wase had
no 2.8 kb band (Matthews et al. 1992)(Fig.
3). The pattern for mitochondrial
DNA(ATPase a) also suggests a genetic difference between diploid and triploid
cultivars.
Therefore the diploid
cultivars
and the triploid
cultivars
are different
not only at
ploidy level, but also in genetic background.
Some of the triploids
showed genetic similarity
with both triploidanddiploidlines.
The Akame group exhibited
2.8 kb bands and larger and smaller
bands. Shogatsuman,a minor cultivar collectedfrom Amami Island, Southern
Japan, showed 2.8 kb, 3.4 kb and the smallar bands (Matthews et al.l992)(Fig.
3).
These cultivars
may have been derived from crosses with tropical
diploids
and179

Figure3. Ribosomal
DNA patternof Japanesecultivars
and anAustralianwild taro.
Total DNA of taro was digested with Taq I, separated with gelelectrophoresisand probed with the spacer fragment of taro ribosomal
DNA. For patterns I-VII, the variety names were (I) Eguimo, (II) Wasekohasubaimo, (III) Ishikawa-wase maru, (IV) Daikichi,(V) Shogatsumanamami, (VI) Yatsugashiraand (VII) Okinawa-aokuki.
The Queensland(Qld) pattern was from wild C. esculenta var. aquatilis.

Figure4. Wild taro(Colocasia
esculenta Schott var. aquatilis)
Okanawa Island showing long slender stolons.

in

180

Figure 5. Wild taros growing on river bank, Kunigami village of
Okinawa Island. Larger leaves are Alocasia macrorhiza.
ancestorsof the temperate
triploid.
The flesh textureof the conns andcold-sensitivityof Akame are intermediate
between the diploid cultivars and mostof the triploid
cultivars,
and support this assumption.
Originof diploid

cultivars

The diploid
cultivars may have originatedin the tropicallowlands, where
var. aquatilis is very common and has broad genetic diversity.
The variation in
Okinawa and northern part of Australia
seems very low, possibly
because theseareas are the margins of the natural distribution.
People selected non acrid andtuber-producing
taro for cultivation.
These cultivars are not cold-hardy,
and it isdifficultfor them to become major cultivars in the temperate zone.
Originof triploid

cultivars

Japanese triploids
have smaller bands around 2.0 kb and larger bands
around 3.4 kb in the DNA analysis.
Some Nepalese taro in our collectionin
NIVOT showed similar bands. Most of the triploid
cultivars in Japan have common
mitochondrial
DNA to Nepalese ones. The origin of the triploid
cultivars
may bethe mountainous region in Nepal, Yunnan in China and neighbouring
areas adjacentto the lowlands.
The triploids
are more cold-hardy than the diploids.
The triploid

181

cultivars
were introduced
to Japan from Southern China with tea, mandarin
and the other crops along with the cultural
techniqueof shift planting1971).

oranges,(Sasaki

References
Sasaki,K. 1971. Inasaku Izen (The agriculture
before rice cultivation).
Nippon Hoso Shuppan Kyokai,
Tokyo, pp. 316.(inJapanese)
Kumazawa,S., K. Niuchi and F. Honda 1956. Classificationof taro varieties
in Japan. J. Japan. Soc.
Hortic. Sci., 25:l-10.(inJapanese)
Matthews, P., Y. Matsushita, T. Sato and M. Hirai 1992. Ribosomal and mitochondrial
DNA variationin Japanese tzro(Colocasia
esculenta L. Schott).
Japan. J. Breed., 42: 825-833.
Hirai, M., T. Sato and K. Takayanagi
1989 Classificationof Japanese cultivarsof tzro(Colocasia
esculenta (L.) Schott)based on electrophoretic
pattern of the tuber proteinsandmorphologicalcharacters.
Japan. J. Breed., 39: 307-317.
Matthews, P. 1990. "The origins,dispersal
and domesticationof taro" PhD thesis, The Australian
National University.
Canberra.

(Comment)
Observations

on yam cultivationin Papua New Guinea.

HIDEKAZU TOYOHARA

It is regretablethat Mr. W.L.Akus was unable to attend this workshop topresent his paper on genetic diversityof yams in Papua New Guinea. In his
absence I will relate to the workshop some of my own observationsin Papua New
Guinea during 3 field surveys in 1991, 1992 and 1993.
Yams {Dioscorea spp.) are one of the most important crops in Papua New
Guinea, especiallyin the low lands such as Central, Madang, East Sepik, and Milne
Bay provinces which have seasonal or heavy year round precipitation.
The major
species of yam cultivatedin Papua New Guinea are D. alata and D. esculenta.
Other Dioscorea species are also cultivatedZ). bulbifera,
D. nummularia, D.
pentaphylla
and D. hispida.
In the Nuku area of Sandaun province at an altitude

Figure1. Tubers of the greater yam (Dioscorea alata) grow in manydifferent shapes and sizes.
Some are shown here.

Tokyo Agricultural
University,
Sakuragaoka, Setagaya, Tokyo 156, Japan

184

of about 300m I have under taken field surveys. In this region people engage inshifting
cultivation.
On sloping land people do not cut all the trees since some are usful as asupport for yam vines. Taro (Xanthospma sp.) and banana are planted on areas
with a steep slope to avoid soil erosion and yam is cultivatedon gentle slopes.
Yamis commonly planted on ridges. There are many types of yam anddifferent
types are planted in different
areas. Yams with long tubers are more often
planted on steeper land than cultivars with round tubers. In the Nuku area D. alata

Figure 2. A simple key to identify
the main yam species
in Papua New Guinea

185

is called Nani and D. esculenta is called Bache. We have examined about 70
cultivars of of D. alata and 35 cultivars of D. esculenta on one farm. According
to Laloki Plant Introductionand Horticultural
Station, 118 cultivars of D. alata and83 cultivarsof D. esculenta can be found in Milne Bay Province.
Papua New
Guinea is thus a very rich area for yam genetic resources.
Local people give names to yams based on the morphology
of aboveground parts and roots, texture and where the yam originated.
Local people havea rich knowledge yams and some people can identify yams at a glance. Since yams
are eaten every day it seems that they grow many cultivars to provide somevariation to their meals.
Yamis usually cooked with coconut milk but sometimes they are baked.
Yams are used as a daily food and also at times of special celebrationsuch asduring thanksgiving
ceremonies and marriage.
After yams are harvested they are divided
into two groups. One to eat
immediately
the other group is stored.
Finally
I would like to propose that further research and development on
yam cultivationand processing should be undertaken.

187

Questionsand Answers in Session

M.Hirai(Q):What is the scientific

H.V.Truong(A):M.Hirai(Q):

Dioscorea

In Indonesia

4name of snake gourd?

hispida.

do you have any varieties

with sidecorms?

M.Djazuli(A):So far I have not seen any. However, characterizationcollections
from Mentawai island is not yet complete.

M.Morishita(Q):What are the differences
Jaya, Indonesia.

of recentbetween taro on Mentawai and Irian

M.Djazuli(A):Since the collections
from Mentawai are not yet characterisedcannot say yet. I would expect considerable
differences
considering
differences
which exist between these areas agro-ecologically.

K. Takayanagi(Q):
Taro cultivation
areas may be for commercial
taro commercially.
M.Djazuli(A):Production

J.L.Bacusmo(Q):M.Djazuli(A):Is therecenters

in Indonesia
production.

Ithe

may be subsistence
and in some
Which parts of the country growin Java grow taro as a cash crop.

any breedingof taro in Indonesia?

No.

J.L.Bacusmo(Q):Do you have Xanthosoma, Macrorrhiza,
minor aroids in Indonesia?

Cytosperma and other

M.Djazuli(A):During our explorationin Central Sulawesi, Central and West Java
we found some minor aroids and these accessions we planted in Bogor as
part of the germplasm collection.

188

LTarumoto(Q):In your presentation
you showed three kinds of cultivation
system.
The broader system you showed, would that be for producing seed corms
for the next planting?
M.Djazuli(A):No. Cultivationof taro on rice field
not seed corm production.

V.Ramanatha Rao(Q):Is it appropriate
intraspecificdiversity?

bunds

to use protein

is for corm production

patterns

to study

M.Hirai(A):Taro is probably
outcrossing
and has broad genetic variationeven atthe intra-specificlevel. Protein banding patterns are effective to detect thisdiversity.
I.Shiotani(Q):How many times can mutations
two proteins?

M.Hirai:(A)At the moment I can not answer. We already cloned two CDNA
storage protein genes. In the near future I will be able to answer yourquestion.

T.Yamada(Q):M.Hirai(A):triploidtaro.

Do weedy taros existof taro?

Are there any particularand diploid
cultivars.

M.Hirai(A):Yes diploidmany side corms.

morphologicaltaros produce a singleoftaro even in theand if so how do they differ

I don't think weedy taros exist in either
not know about other regions.

K.Kikuchi(Q):triploid

the pattern

How did it become triploid?

This is not known. We have not found tetraploid
Nepal collection.

D.Vaughan(Q):relatives
M.Hirai(A):You discussed

occur to differentiate

from wild

Okinawa or Australia.

differences

I do

between thelarge main corm and triploids

have

189

K,Kikuchi(Q):Wouldyou please

explainthe breeding

M.Hirai(A):Only a few prefecturalresearch
However this is a very small effort.

stationsof taro in Japan?
have some breedingof taro.

GENERAL DISCUSSION

Chairmen
V. Ramanatha Rao
Itaru Shiotani

193

General Discussion
K. Kawano(Q):Given that the CGIAR Centers can take care of, by and large, allaspects of germplasm management in major crops, what would be the longterm role of IBPGR?
V. Ramanatha Rao(A): Based on the needs expressed by the national programs,
IPGRI will assist in genetic conservation of root and tuber crops in any way
it can. It will highlightthe need for complementary strategies
forconservation,
develop appropriate
methodologies
and guidelines
for this
purpose. Its level of support will, however, depend on the donors support
for the issues that have been raised during the meeting.

K, Kawano(Q):In the wake of "intellectual
property right"(IPR)
concerns mainly
from the developed countries and so-called "germplasm nationalist1
on thepart of developing countries in the tropics.
Can you explain where IBPGR
stands in these topics?
Can IBPGR contribute to sorting out the possible
conflict?
V. Ramanatha Rao(A): National sovereignly
on genetic resources is not limiting
the exchange of germplasm. It may lead to some amount of control, but
a country is free to evolve its own regulations.
However, IPGRI willcontinue to promote free exchange of germplasm. Coming to IPR, IPGRI,
along with the other CG centers does not recognise IPR of plant genetic
resources. IPGRI has an internal taskforce to follow the internationalscene
and can play an advisory role to national programs, if requested.

I. Shiotani(Q):You mentioned about 100 root and tuber species belonging
to 22
genera which are used for various purposes in subsistence economies. Dr.
Truong also mentioned 58 useful minor root crops in Vietnam. I supposethat there are quite alot of these plants that are wild and semi-cultivatedaswell as the cultigens.
I am very interested
in these species. In the near future, germplasm to be
used for crop improvement will be extended to the remote species throughmethods of DNA manipulation.
Does IBPGR have a project to collect andpublish informationon these natural resources including
wild relatives
ofmajor root and tuber crops?

194

V. Ramanatha Rao(A): There are numerous root and tuber crops that are used bypeople in developing
countries as indicatedearlier by me and Dr. Ho
Truong. Information on some of them will be covered under a German
supported IPGRI project on 'neglected crops'. Efforts also will be made togather informationon other useful species. As far as possible information
on wild relatives will also be gathered.

M. Oka(Q):Weevil causes serious damage on sweet potato in Asian countries
includingthe south western islands of Japan.
Is there any specific genetic resources showing weevil resistance.
If thereare not, can we find such materials from the many genetic resources kept
at agricultural
institutes
around the world?
How about an international
research network system for finding weevil resistance?
J. L. Bacusma(A):Our work in the Philippines
has not revealed any weevil
resistantmaterials. AVRDC has done much more work on this topic.
K. Koniaki(A):As far as I am aware AVRDC has not been successful in finding
weevil resistance.
It is my opinion that weevil resistance will not be foundsince it would be very difficult
to protect the whole edible tuber from theweevil.

M. Nakagahra(Q):Safe, cost effective and simple methods to conserve root andtuber crops is very important.
What kinds of efforts are being made to
develop such systems for different
crops and in different
countries.
C. Thiraporn(A):in vitro.

In Thailand

our cassava collection

is maintainedin the field

J. L. Bacusmo(A):In the Philippines
we maintain most of our germplasm
field or in pots. A little is also conserved in vitro.

andin theT. Ishige(A):We are concerned mainly with the maintenanceof a working
collectionof about 2000 lines. Since this is research material not a genetic
resources collection
we have our own interests in mind when maintaining
this collection
and can thus find the resources to do so. This may notalways the case for those maintaining
large germplasm collections.
M. Djazuli(A):Our collectionof taro is not so large so we can maintainin the195

field.
However resources to evaluate the material are limited and we will
face problems maintaining
the collection
if it grows much bigger.

D. A. Vaughan(Q):I would like to ask about in-situ on farm conservation of root
and tuber crops. In-situ (on farm) conservation seems to offer a usefulmeans of conservation of root and tuber crops:
Would Professor Shiotani comment on whether there is any possibility
forpromoting on farm conservationof traditionalvarieties
in Japan where
many tradional varieties
apparently
grow in isolated pockets as his paper
indicated?.
Could Professor Bacusmo comment on work being conducted on in situ
conservation efforts in the Philippines
and its practicability?
I. Shiotani(A):Replacement of many traditionalvarieties occurred in a short periodof time during the 1950's and early 1960's. Progress and loss comes
together. I could quote a Japanese proverb 'lucky and unlucky are twisted
in a thread'. The best way to keep diversity
on the farm is to stop breeding
efforts but this is hardly practical.
Local agriculturalactivity
is mostimportant to keep genetic diversity
on the farm. We need to look for new
breeding systems which maintain genetic diversity
in local agriculture.
J. L. Bacusmo(A):This is a difficult
question.
In the Philippines
there is a CIP
project called UPWARD which started a project on 'memory banking' thatis a project to record information
on varieties
in farmers memories. The
project consistedof asking lots of questions to farmers understand their
genetic resources better and to help get a lead in evaluating
varieties.
Breeders and a social scientist
were involved in this project.
The projectprogressed
into a community based genebank project in the hope ofconvincing people to do something with there own genetic resources. This
project may be difficult
to sustain because sweet potato is not an indigenous
crop to the Philippines
and it is an economic crop only of use if the pricefor it in the market is good. The concept of in-situ conservationis tocompliment ex-situ efforts. Giving communities the opportunity
to plant
different
varieties of a crop in a kind of gene reserve is a good idea. In situ
conservation might be sucessful in the Philippines
for indigenous crops andwild relatives of crops, such as wild yams, for which their forest habitat canbe protected.

196

J.L.Bacusmo(Q):Can you explain
exchange of sweet potato.

Japaneseprinciples

regarding

germplasm

M. Nakagahra(A):Japan freely exchanges germplasm with other countries.
Requests for germplasm in the MAFF genebank system should be addressedto the Director General of NIAR(Kannondai
2-1-2, Tsukuba, Ibaraki,
Japan. Fax: +81-298-38-7408).
He can then direct the request to theappropriate
researcher to respond.
The only 'germplasm' which cannot be released immediatly
are recently
registeredvarieties for which a period of 4 to 5 years after registrationarenot distributed
from the genebank system of Japan. The reason for this isthat these varieties
are initially
protected
by the Japanese law of seed andseedlings.

WORKSHOP SUMMARY

V. Ramanatha RaoSummary
V. RAMANATHA RAO1

From the technicalpapers that were presented on various crops I would
highlight
the following
issues which emerged from the last two days of discussion
as being important:
there are considerable
gaps in the collections
for many crops. Taro, forexample, is poorly collectedin the area it is consideredmost diverse and still no
tetraploidtaro has been found according to Dr. Hirai.
Eco-geographic
andethnobotanicalstudies to identify
areas rich in genetic diversity
are needed. Dr.
Truong indicated much more can be learnt about root and tuber crops in Vietnam
from such an approach.
strategies and methods for characterisationand evaluation need to be
improved. Wild relatives of root and tuber crops need to be a part of this process.
The importance of finding good sources of resistance to the sweet potato weevil
was highlighted
by several participants.
documentation needs of different countries and institutions
are at various
levels of development and need improvement. In this regard, IBPGR has recently
produced software and self teaching manuals (genebank management system) whichmight go some way to helping satisfy this need.
at present nearly all the focus of attention regarding root and tuber crops
is on the "big three" namely the potato, cassava and sweet potato.
Only limited
efforts are directed towards taro and yams. While many minor, but locally very
important, root and tuber species, to borrow the words of Dr. Kawano, "appear
doomed to extinction"
unless appropriate
action is taken.
muchresearch is needed in developing
conservation methods, particularly
to make them cost effective.
Clearly the conservation
methods which may beappropriate
in one country may not be in another.
For example, a reliable
cryopreservation
system may be possible in Japan, however in countries where theneeded supplies are not readily available
alternative
approaches may be necessary.

International Board of Plant Genetic Resources,
Asia Pacific Oceania Office, Singapore

200

a complementary conservation strategy is essential
for root and tuber
crops. In situ conservation, by which I include on-farm conservation, offers realpossibilities
for many root and tuber crops. Many minor root and tuber crops areeither semi-domesticatedor wild and their habitats
could be protected.
For
conservation of farmers varieties,
it was pointed out by Dr. Bacusmo that in situ
conservation
could be effective.
However, he indicated,
it is best to focus on a
species which is indigenous
to a locality
and not introduced.
Additionally,
the feltneed by farmers to maintain diversity
is an important consideration
for the successof in situ conservation
the poor knowledge on the ancestry of many root and tuber crops
highlights
the need for more attention to be paid to wild species.
This seems
particularly
importantin the 1990's
when biotechnology
permits
somatic
hybridization, as discussed by Dr. Ishige, and other means of using distant relativesof crops.
ready exchange of root and tuber crops is hampered by the need for
careful attention
to quarantine procedures.
Movement of cassava from Africa toSouth America is restricted
due to quarantine concerns, as pointed out by Dr.
Kawano. Safe means of overcoming some of these problems are needed so that
useful germplasm is available
to people worldwide.
Effortsof IBPGR indeveloping guidelines
for the safe movement of germplasm are directed towards thisgoal.

This workshop has highlighted
how dependent countries are on one anotherfor plant germplasm. The pedigree charts shown by several speakers from Japanfor different
crops illustrated
this point well. So there is a need for increased
collaboration
assistedby internationaland regional agencies.
Japan, with its
scientificexpertise and leading economic development, is in a position to assist in
various collaborative
ventures in the region both by expanding work on strategic
research as well as by contributing
necessary funds to promote work on the issuesof conservation and use of root and tuber crops in the region.
As far as I know, international
institutes
operating in the region are sincere
in their efforts and will definitely
do whatever they can to assist the national
programs. With further assistance from donors, it should be possible to do more inthis area. It is also essential
to increase allocations
on the so called neglected or
locally important species as they play a major role in subsistence
agriculture.
Itshould also be possible to encourage "green marketing" for such products so thatcultivationof these could be expanded and diversity be maintained on the farm.
To conclude, the two days deliberations
have been very useful inexchanging
informationand ideas.
I hope this will also lead to increased
collaboration
work on root and tuber crops.

CLOSING

Masahiro

REMARKS

Nakagahra

Closing

Remarks

MASAHIRO NAKAGAHRA1

Thank you very much Dr. Rao and Dr. Shiotani for your excellent summaryof the discussion.
We have now come to the end of all the sessions.
On behalf of theorganizing committee of the workshop, I should deliver a few words.
First of all, I would like to thank all the chairpersons,speakers, and otherparticipants
for their valuable contributions.
I would also like to express ourthanks to the cooperating
institutes,
NARC, JIRCAS and FTRS in Tsukuba for
helping
to organize this workshop successfully.
I am thankful to Agriculture,
Forestry and Fisheries Research Council for providing us with full financial
supportfor this workshop.
The MAFF International
Workshop on Genetic Resources aims at
promoting research exchange and collaborationon the development of technologies
and global strategies
for conservation
and use of genetic resources in national
programs and the international
research institutions.
The subject of root and tuber
crops was the first focus during this workshop to learn about the present status inthis area.
Dr. Rao mentioned yesterday that he often considers the Science of Genetic
Resources as the Science of Crisis.
We hope by increased commitment toconserving genetic resources the crisis will lessen.
Weprepared a program consistingof keynote addresses and four technicalsessions.
In keynote addresses, "The Role of internationalorganizations
in root
and tuber crops conservation" and "The Utilizationof root and tuber crop genetic
resources in Japan" were presented.
Technical sessions dealt with present status
and current research topics on root and tuber crops genetic resources, in which 14
reports were presented.
In general discussion,
the importance of in situ and in
vitro
conservation
were highlighted,
of cooperation
among countries
andinternationalorganizations
in overcoming quarantine problems in transportationofgenetic resources, exploration,exchange of materials and information.
Thus, during this workshop, we shared a great deal of information
on root
and tuber crop genetic resources.
We understand that these genetic resources areplaying an important role in food production for millions of peoples in the world.

Genetic(NIAR),

Resources Coordinate!:,National
Tsukuba, Ibaraki 305, Japan

Instituteof Agrobiological

Resources

204This workshop is small scale and a first, but I anticipate
that by continuingthese efforts in the future, we will contributeto further promotion of exchange andstrengthen of research collaborationin conserving genetic resources.
On behalf of all the members of the organizing
committee, I wish to
express our sincere gratitude to all of you who have so actively participatedin thisworkshop to make it such a success. I thank you, all the distinguishedguests andparticipants
again, for their active participationand cooperation.
I would like toextend my best wishes to all of you for your work in your countries
andorganizations.
I and all the staff members of Tsukuba institutions
are looking
forward to seeing you again in the future.
Wewill have one more day for a field workshop tomorrow. Now I havethe duty and the honor to declare the Indoor-workshop
closed.
Thank you very much for your kind cooperation.

LIST OF PARTICIPANTS

MAFF International

Workshopon Genetic Resources
Root and
Tuber

March 14-16,
Crops

1994,

Tsukuba,

Japan"

208

Aoki, Toshimitsu
Agriculture,
Japan(Secretarial
Forestry

Bacusmo, Jose Lastimosa
Director, Philippine
Djazuli,Fujimaki,Staff)and Fisheries

Research

CouncilSecretariat,

MAFF,(Session 3 and Session 2)
Root Crop Research and Training

Center,Philippines

Muhamad (Session 4 and Session 1)
Plant Physiologist,
Bogor Research InstituteIndonesia(Secretarial
Staff)
Genetic Diversity,

Masamichi
Head, Lab. Genetic
Experiment Station,
Sarurnina
National
Philippines,

D.
Sciences
Research(JIRCAS -Okinawa)

Guo, Xiaoding
Xuzhou Sweet Potato

Hoshino,

NIAR, MAFF, Japan

Resources Utilization,
MAFF, Japan

Hasan, Sayed M.
Faculty of Agriculture,
Universiti(JIRCAS -Okinawa)

Hirai,CRIFC,

NIAR, MAFF, Japan

Furukawa, Chikara (Secretarial
Staff)
Head, Lab. Animal Genetic Diversity,

Halos,

Crops,

Hiroshi (Opening Address)
Director General, NIAR, MAFF, Japan

Fukuoka, Shuichi
Lab. Plant

Furuya,for Food

Institute,

Pertanian

Research

TohokuNational

Agricultural

Universityof thePhilippines,

Malaysia,

Malaysia,

Center, China

Masashi (Session 4)
Head, Lab. Vegetable Breeding I, National Research InstituteOrnamental Plants and Tea, MAFF, Japan
Takafumi (Organizing
Committee)
Director, Dept. Crop Development, NARC, MAFF, Japanof Vegetables,

209

Irie,

Kenji
Faculty

Ishige,of Agriculture,

Tokyo University

Teruo (Session 2)
Head, Lab. Plant Cell Breeding,

Iwanami, Setsuo (Secretarial
Staff)
Head, Research Coordination
Izaike,Institute,

Division,

Katsuta,

Ibaraki

Agricultural

Diversity,

Staff, Session 3)
Resources, JIRCAS,

Masumi (Secretarial
Staff)
Lab. Plant Genetic Diversity,

NIAR, MAFF, Japan

NIAR, MAFF, Japan

Kaku, Hisatoshi(Secretarial
Staff)
Head, Lab. Microorganism
Genetic
Kato, Shinjiro(Secretarial
Div. of Biological

Fumio (Organizing
Faculty of Agriculture,

Kobayashi,
Hitoshi
Director General,

Center,Japan

NIAR, MAFF, Japan

MAFF, Japan

NIAR, MAFF, Japan

Kawano, Kazuo (Session 1 and Session 4)
Gene Pool Breeder for Asia and Coordinator,
Program, CIAT, Thailand
Kikuchi,Japan

NIAR, MAFF, Japan

Yoshiaki(Secretarial
Staff)
Head, Lab. Animal Conservation,

Izumisawa, Tadashi
Agricultural
Researchof Agriculture,

Cassava AsianCommittee, Session 3)
Tokyo Universityof Agriculture,

Regional

Japan

NARC, MAFF, Japan

Komaki, Katsumi (Secretarial
Staff, Session 3)
Head, Lab. Sweet Potato Breeding, NARC, MAFF, Japan
Li, Yung Sheng
Lab. Cell Breeding,
Makita,MichioDirector,
Fisheries

NIAR, MAFF, Japan, (P. R. China)(Organizing
Committee)
Liaison and Coordination
Division,
Agriculture,
Research Council Secretariat,
MAFF, Japan

Forestry

and

210

Makita,MichioDept. of Genetic

Resources II, NIAR, MAFF, Japan

Masuda, Taizo
Lab. Soil Conservation
and Improvement,
Experiment Station, MAFF, Japan

Kyushu National

Agricultural

Minobe,Yuzo (Organizing
Committee)
Director,
Dept. of Genetic Resources I, NIAR, MAFF, Japan

Miyashita,

Susumu (Secretarial
Staff)
Germplasm Storage Center, NIAR, MAFF, Japan

Miyazaki,

Shoji
Director,(Organizing
Committee, Session 1)
Div. of Biological
Resources, JIRCAS,

Mori, Motoyuki (Session 2)
Lab. Potato Breeding, Hokkaido
MAFF, Japan
Moriguchi,
Takaya (Secretarial
Lab. Breeding IV, Fruit
Morishita,

Nagae,

Nagata,Masahiro
Osaka Prefectural
KeiichiNational

CenterStaff)
Tree Research

Agriculturalfor Seeds

National

Agricultural

Station,and Forestry

and Seedlings,

Toru (Organizing
Committee)
Director,
Dept. of Research Planning
Japan

MAFF, Japan

Station,

MAFF, Japan

ResearchCenter,Japan

MAFF, Japanand Coordination,

Nakagahra,
Masahiro (Organizing
Committee)
Genetic Resources Coordinator,
NIAR, MAFF, Japan
Nakayama, Hiroki (Secretarial
Staff)
Lab. Plant Genetic Diversity,
NIAR, MAFF, Japan
Nakayama, Shigeki(Secretarial
Lab. Plant Conservation,

Experiment

Staff)
NIAR, MAFF, Japan

NIAR,

MAFF,

211

Oank, Hoang Kim
Lab. Cell Breeding,
Ohara,

NIAR, MAFF, Japan, (Vietnam)

Akiko
Lab. Potato Breeding,
MAFF, Japan

Hokkaido

National

Oka, Mitsunori(Secretarial
Staff, Session 1)
Div. of Research Information,
JIRCAS,
Okuno, Kazutoshi (Secretarial
Staff)
Head, Lab. Plant Genetic Diversity,
Ono, Machiko
Nagoya Women's University,
Ooishi,

Oyanagi,

Agricultural

Experiment

Station,

MAFF, Japan

NIAR, MAFF, Japan

Japan

Takao (Organizing
Committee)
Director, Dept. of Genetic Resources

II, NIAR, MAFF, Japan

AtsushiLab. Wheat and Barley

NARC, MAFF, Japan

Physiology,

Rao, V. Ramanatha (Keynote Address and Workshop Summary)
Regional Office for Asia, the Pacific and Oceania,
IPGRI, Singapore
Sakaguchi,
Susumu (Organizing
Committee, Session 2)
Agriculture,
Forestry and Fisheries
Technical Information
Sakai,

Sakura,Sanada,Shiotani,

Society,Japan

Society,

Japan

MAFF,

Kenkichi(Organizing
Agriculture,
Forestry

Committee,
and Fisheries

Keynote Address)
Technical
Information

Reiko
Agriculture,Japan

and Fisheries

Research

CouncilSecretariat,

Tree Research

Station,

MAFF, Japan

Forestry

Tetsuro (Secretarial
Head. Lab. Breeding
Itaru
Faculty

Staff)IV, Fruit(Keynote Address and General Discussion)of Bioresources,
Mie University,
Japan

212

Shirata,

Kazuto (Secretarial
Staff)
Head, Lab. Plant Conservation,

Suematsu, Akio (Session 2)
Seed inspector,
National
Sugiura,Suzuki,Suzuki,Takagi,

MakotoLab. Crop resources
MAFF, Japan
Kenji
Chiba Prefectural

NIAR, MAFF, Japan

Center for Seeds and Seedlings,

Shikoku

Agricultural

National

Agricultural

Experiment

Station,ShigeruTeam Leader, JICA Projectof Genetic

HirokoOkinawa Branch, JIRCAS,

MAFF, Japan

YasuhiroLab. Crop Quality,
MAFF, Japan

KyushuTakayanagi,
Kenji (Organizing
Faculty of Agriculture,
Takeya,Tamiya,Tanifuji,Agricultural

Chile

Forestry

Experiment

NIAR, MAFF, Japan

NARC, MAFF, JapanTokyo University

Kagoshima

Prefecturalof Agriculture,

Japan

Biotechnology

Institute,andStation,Committee, Session 4)
Universityof Tsukuba, Japan

Seiji (Secretarial
Staff)
Lab. Sweet Potato Breeding,

Tarumoto, Isao
Director General,

Station,Japan

General), Agriculture,
MAFF, Japan

National

Masaru (Secretarial
Staff)
Lab. Germplasm Database Systems,

Hironori
Facilityof Agriculture,

Experiment

Resources Conservation,

Takahashi,
Teiji (Welcome Address)
Research Councillor(Deputy Director
Fisheries
Research Council Secretariat,
Takahata,

MAFF, Japan

Japan

213

Teramoto, Sayuri (Secretarial
Staff)
Lab. Breeding IV, Fruit Tree Research Station,
Thiraporn,
Charn (Session
1)
Root and Tuber Crops Specialist,
Agriculture,Thailand

Field

MAFF, Japan

Crop ResearchInstitute,

Dept. ofTomooka, Norihiko (Secretarial
Staff)
Lab. Plant Genetic Diversity,
NIAR, MAFF, Japan
Toyohara, Hidekazu
Faculty of Agriculture,
Truong,Tsuchiya,

Tsuchiya,
Ushitani,

Ho van (Session
Director, National

Tokyo Universityof Agriculture,

4 and Session 3)
Instituteof Agricultural

Ken'ichi(Secretarial
Staff)
Head, Lab. Microorganism Conservation,

Science,Vietnam

NIAR, MAFF, Japan

Shichiro(Organizing
Committee)
Director, Dept. of Breeding, Fruit Tree Research
Katsunori
Agriculture,
Japan

Japan

(Organizing
Committee)
Forestry and Fisheries
Research

Station,Council

MAFF, Japan

Secretariat,

MAFF,

Vaughan, Duncan Alexander (Editorial
and Secretarial
Staff)
Lab. Plant Genetic Diversity,
NIAR, MAFF, Japan
Yamada, Toshiaki(Secretarial
Staff)
Head, Lab. Wheat and Barley breeding
Yamakawa, Osamu (Session 3)
Head, Lab. Sweet Potato
Breeding,
Experiment Station, MAFF, Japan

Technology,

KyushuNARC, MAFF, Japan

National

JIRCAS:
Japan International Research Center for Agricultural
NARC: National Agriculture
Research Center
NIAR: National Instituteof Agrobiological
Resources

Agricultural

SciencesPublishedbv

March. 1995.

Research Council Secretariat of MAFF andNational Instituteof Agrobiological
Resources (N.I.A.R.)
2-1- 2 kannondai, Tsukuba, Ibaraki 305, JAPAN