Kagoshima University Research Center for the Pacific Islands Occasional Papers No.39, 93-98, 2003
Section 3, Report 2. The Progress Report of the 2000 and 2001 Survey of the Research Project“Social Homeostasis of Small Islands in an Island-zone”

93

CLASSIFICATION OF CITRUS SPECIES ON YAP ISLAND AND ULITHIATOLL OF THE FSM
TOMINAGA Shigeto＊1), YAMAMOTO Masashi1) , KOHNO Rumiko1),
PARK Byoung-Jae2), TSUDA Katsuo1), ONJO Michio 1) , and ICHITANI Katsuyuki1)

Abstract
The Citrus spp. found on Yap and four inhabited islands of the Ulithi Atoll (Mogmog, Falalop,Asor, and Fassarai Islands) of Yap State of the Federated States of Micronesia (FSM) were collected
and classified to the species level using morphological characteristics and isozyme analysis. Citrus individuals collected on Yap Island were determined to belong to one subgenus, six species, and threewere hybrids between species while those collected on Mogmog and Falalop Islands belonged to threespecies. On both islands three hybrids between species were identified among the individuals collected. On the other hand citrus collected on Asor Island were classified into two species and one hybrid while those samples collected on Fassarai Island belonged to two species.
Keywords: citrus, isozyme genotype, morphological character, Yap Island, Ulithi AtollIntroduction
Although environmental conditions would allow for the production of citrus in Yap State of
the Federated States of Micronesia (FSM), citrus production in Yap State and the FSM has not
become an agricultural industry of economic importance (TOMINAGA et al. 1995b). Tropicalfruits, including citrus, are grown throughout the FSM by home owners for personal consumption (TOMINAGA et al. 1995a)
A survey of the distribution of Citrus spp. grown on Yap Island and four inhabited islands(Mogmog, Falalop, Asor, and Fassarai Islands) of the Ulithi Atoll was conducted. Seventy-one
samples consisting of leaves, fruit, and shoots of the citrus species surveyed were collected andthe individuals were classified based on morphological characteristics (leaf and fruit shape, number and color of the seed, embryony) and the isozyme genotype of the leaf enzymes.
Additionally the Brix and acidity content of the fruits were determined. Since flowers were notavailable for botanical classification purposes, the classification to the species level was basedon both morphological and isozyme data to ensure accuracy.

Materials and Methods
The survey of Citrus spp. was carried out on Yap and the four inhabited islands of the Ulithi
Atoll from October 17 to 30 of 2001. Sample collection consisted of thirty-nine Citrus spp. samples collected on Yap, twelve samples collected on Mogmog, ten samples collected on Falalop,four collected on Asor, and six citrus samples collected on Fassarai Island for a total of 71 Citrus＊)

Author for correspondence. Fax +81 992858552, e-mail tominaga@agri.kagoshima-u.ac.jp
Faculty of Agriculture, Kagoshima University. Kagoshima 890-0065, Japan.
2)
United Graduate School of Agriculture Sciences, Kagoshima University. Kagoshima 890-0065, Japan1)

94

T OMINAGA Shigeto, YAMAMOTO Masashi, KOHNO Rumiko, PARK Byoung-Jae, TSUDA Katsuo, O NJO Michio, and ICHITANI Katsuyuki

spp. samples collected. A sample consisted of 30 leaves and 3 fruits from each tree except when
the tree had no fruit then only 30 leaves were collected.
At the time of sampling, morphological characters such as leaf shape, presence and shapeof leaf wings, leaf flavor, fruit shape, stylar end convexity, fruit diameter and weight, fruit shapeindex, and rind color were determined. Using these data, the morphological classification wasdone according to the scheme developed by I WAMASA (1976). The samples were then frozen
and conveyed to Kagoshima University for flesh weight, percent flesh, seed number, seedweight, embryony, embryo color, Brix and acidity determinations and isozyme analysis. Isozyme
analysis consisted of glutamate oxaloacetic transaminase (GOT) and peroxidase (Px) content determinations which was then related to sample genotype. The methods described by Y AMAMOTOet al. (1998) were used to determine isozymes and leaf genotype and subsequent classification
into species using these data were determined by the method of H IRAI et al. (1986, 1987). Alldata were used to categorize each sample into species. The species were described according tothe classifications developed by SWINGLE (1967).

Results and Discussion
Yap Island
Based on the morphological characters of the 39 samples collected on Yap Island, the samples could be classified into eight citrus groups. Six samples were papedas, 3 were pummelos,
10 sweet oranges, 6 ponkan mandarins, 6 calamondins, 4 sour oranges, 1 lime and 3 unidentified citrus (Table 1). On the other hand, isozyme genotyping resulted in a classification of
the citrus samples into 5 papedas (Purutt), 3 pummelos, 7 sweet oranges, 4 mandarins (Indiatype), 5 mandarins (China x India type), 6 calamondins, 3 sour oranges, and 6 un-identified citrus (Table 1). Based upon morphological characters, isozyme genotype, and embryony the Citrus
spp. collected on Yap Island belong to 1 subgenus papeda and 38 species and hybrids. And thespecies and hybrids within the 38 samples were 3 pummelos (Citrus grandis (L.) Osbeck), 2 souroranges (C. aurantium L.), 5 sour orange hybrids (C. aurantium hybrid), 1 lime hybrid (C.
aurantifolia hybrid), 3 papedas (Purrut) (C. hystrix DC.), 2 papedas hybrids (C. hystrix hybrid),
6 calamondins (C. madurensis Lour.), 7 sweet oranges (C. sinensis (L.) Osb.), and 9 mandarins(C. reticulata Blanco). The nine mandarins identified were of two types, the India and the Chinax India type (Table 1).
Mogmog Island
The 12 samples collected from citrus plants growing on in Mogmog Island were classified,using morphological characteristics, into 4 groups. Six of the samples were papedas, three werecalamondins, one was sweet orange and 2 were un-identified citrus. Isozyme genotyping revealed that the genotype of the Mogmog Island samples could be separated into 6 papedas(Purutt), 2 calamondins, 1 sweet orange, and 2 un-identified citrus. When the classification
scheme is based upon morphological characters, isozyme genotyping, and embryony the citrus
samples could be separated into 5 papedas (Purrut) (C. hystrix DC.), 1 papeda (Purrut) hybrid(C. hystrix hybrid), 3 calamondins (C. madurensis Lour.), and 1 calamondin hybrid (C.
madurensis hybrid), 1 sweet orange (C. sinensis (L.) Osb.), and 1 sour orange hybrid (C.
aurantium hybrid) (Table 2).
Falalop Island
Based on morphological characters the 10 samples collected on Falalop Island were

CLASSIFICATION OF CITRUS SPECIES ON YAP ISLAND AND ULITHI ATOLL OF THE FSM95classified into 3 groups (2 limes, 2 lemons, and 6 papedas). Isozyme genotyping resulted in classifying the same samples into four groups (6 papedas (Purutt), 1 Tahiti lime, 2 lemons and 1 unidentified citrus). When morphological characters, isozyme genotype and embryony were used
as classification tools, the same samples fell into seven groups (5 papedas (Purrut) (C. hystrixDC.), 1 papeda (Purrut) hybrid (C. hystrix hybrid), 3 calamondins (C. madurensis Lour.), 1Tahiti lime (C. aurantifolia Swing.), 1 Tahiti lime hybrid (C. aurantifolia hybrid), 1 lemon (C.
limon Burm. f.), and 1 lemon hybrid (C. limon hybrid) (Table 3).
Asor Island
The four samples collected on Asor Island when classified using only morphological characters could be placed into three groups (1 papedas, 2 calamondins, 1 lime). Isozyme genotyping revealed that the same samples could be classified into two groups (1 papedas (Purutt) and 3
calamondins). When morphological characters, isozyme genotype and embryony were used asclassification tools, the four samples fell into three groups (1 papedas (Purrut) (C. hystrix DC.), 2
calamondins (C. madurensis Lour.), and 1 calamondin hybrid (C. madurensis hybrid)) (Table 4).

Fassarai Island
Classification of the six samples collected on Fassarai Island using morphological characters only, placed the samples into two groups (5 papedas and one lime). Isozyme genotyping
placed the samples into two groups as well (5 papedas (Purutt) and 1 Tahiti lime). When morphological characters, isozyme genotyping, and embryony were used as classification tools, thesamples could again be grouped into two groups (5 papedas (Purrut) (C. hystrix DC.) and 1
Tahiti lime (C. aurantifolia Swing.)) (Table 5).

Acknowledgments
The authors are grateful to Prof. G. A. Couvillon, University of Georgia, for proof reading
the manuscript.

References
H IRAI, M. and K AJIURA I. 1987. Genetic analysis of leaf isozymes in citrus. Japan J. Breed. 37:377–388.
H IRAI, M., K OZAKI I., and K AJIURA I. 1986. Isozyme analysis and phylogenic relationships ofcitrus. Japan J. Breed. 36: 377–389.
IWAMASA, M. 1976. Kankitsu no hinshu [Cultivars of citrus]. Shimizu, Japan: Shizuoka Citrus
Grower’s Coop. Assoc. 255 pp.
SWINGLE, W. T. 1967. The botany of citrus and its wild relatives. Citrus Industry, vol.1, ed. byW. REUTHER et al., 190–430. Berkley: Univ. Calif.
TOMINAGA, S., O NJO M., HAYASHI M., A. S. L ORENS, and H ASHINAGA F. 1995a. Characteristicof tropical and subtropical fruits collected island of the FSM. Kagoshima Univ. Res. Center
S. Pac. Occasional Papers 26: 9–13.
TOMINAGA, S., O NJO M., H AYASHI M., and A. S. LORENS. 1995b. Distribution of citrus species
on Pohnpei Island of the FSM. Kagoshima Univ. Res. Center S. Pac. Occasional Papers 26:
15–21.
Y AMAMOTO, M., M ATSUO Y., KUNIGA T., M ATSUMOTO R., and Y AMADA Y. 1998. Isozyme andRAPD analyses of Shiikuwashas (Citrus depressa Hayata). Bull. Natl. Inst. Fruit Tree Sci.
30 殴 31: 39–51.

No

Le afwingwx
Fruit
Em bryoIsozyme genotype
Species assumed byStylar
Seed
Acidity
WeightShapeFlesh
end
BrixColoury
Got-1
Got-2Px
M orphology
Isozyme analysis
Number Em bryony(%)(g)
index(%)
convex1LN
1058
1146142
M ono
C8.60.5FFMMBB2
M
N94212051
5M onoC
10.50.3
FF
MMBB
PummeloPumme lo
3M
No fruit
FFMMBB
4M
N
73
1256443Poly
PG
7.5
1.7
FF
MM
CC
PapedaUn- identifie d5NC
107
86
63
06.8
1.2
FS
MMDD
Sour orange
Un- identifie d6NC
60
9778
9
M ono
NG
7.7
1.9
FS
MMCC
Lime
7NN
48
9969
12PolyG
8.11.7FS
MMCC
Un- identifie dSour orange
8NC
789473
16PolyG7.91.9FS
MM
CC
9S
N
227
1105427
M ono
C
8.10.4SAMM
BD
10S
N
127
1046936
PolyPG
8.10.5SAMM
BD
Sweet ora nge Sour or ange
11S
N
261
10562
42
Poly
C
7.80.6
SA
MM
BD
12L
C
3162
58
10
M ono
G
8.6
1.5
SM
MM
CC
13L
C
2366
496
M ono
NG
9.21.9SM
MM
CC
14
L
C
2270
58
6
Poly
G
9.4
1.9SM
MM
CC
PapedaPapeda (Purrut)
15
LC
2861435PolyG
9.61.9SM
MM
CC
16LC
23544708.61.1SM
MMCC17NN
28109736PolyG
7.20.6SM
MMDF
18N
N
27109768PolyNG
10.81.0SM
MMDF
19NN
21111
767PolyG
8.41.2SMMMDFCalamondin
Calamondin
20NN
24114768Poly
PG
11.51.0
SM
MM
DF
21N
N
28109
797PolyG
8.41.0SM
MM
DF
22N
N
33115
11Poly
G
SM
MMDF
23
SN
248
1056137
M ono
C
7.90.6SS
MMBD
Sour orange
Un- identifie d
24S
N
209
100
9516PolyPG
7.60.8SS
MMDD
25NN
174
107
7418PolyPG
10.10.3SSMMDD26NN
266
9370
25
PolyC
7.70.3SS
MM
DD
Sweet ora nge
27
NN
225
9765
16
PolyC
7.60.2SS
MM
DD
Sweet orange
28
N
N
193
104
7225
PolyC
8.20.4
SS
MMDD
29N
N
285
102
72
29
Poly
C
8.40.3SS
MMDD
30
S
No fruitSS
MMDD
Un-ide ntif ied
31
S
N
336
102
646
Poly
PG
7.90.2SS
MM
CC
Sweet ora nge
32
N
No fruitSS
MMCC
Mandarin (India
Un-ide ntif iedtype)
33
N
No fruit
SSMM
CC
34
N
No fruit
SS
MMCC
35
N
No fruitSS
MMCD
36NN108118727
Poly
G
8.50.7SSMM
CD
Mandarin (ChinaPonkantype x India type)
37
NN
171
1226910Poly
G
8.60.4SSMMCD
38NN
165
121759PolyG
8.60.2SSMMCD
39NN
13511653
15
Poly
G
8.40.4SS
MM
CD
Abbreviations, wL=Large, M=M edium, S= Small, N=Without wing, xC =With convex, N=Without convex, y PG= Pale green, C= Cream, G=Green, NG=Nile green,zS pec ies classification based on Swingle (1967).

Table 1. Characteristics of leaves and fruits of citrus collected on Yap Island of the FSM

C . reticulata B lanco

C . reticulata B lanco

C . sinensis (L.) Osb.

C . aurantium hybrid

C . madure nsis Lour.

C . hystrix DC.

C . hystrix hybrid

C . hystrix DC.

C . aurantium L.

C . aurantium hybrid

C . aurantium hybrid

S ubgenus pa peda
C . aurantium hybrid
C . aurantifolia hybrid

C . grandis (L.) Osb.

z

Species identified
by m orphology andisozyme analysis

96
T OMINAGA Shigeto, YAMAMOTO Masashi, KOHNO Rumiko, PARK Byoung-Jae, TSUDA Katsuo, O NJO Michio, and ICHITANI Katsuyuki

Le afwwing

No

Le afw
wing

Fruit
Em bryoIsozyme genotype
Species assumed byStylarx
SeedAcidity
end
WeightShape
FleshBrix
Number Em bryony(%)
Coloury
Got-1
Got-2
Px
M orphology
Isozyme analysis
convex
(g)
index
(%)
1
NC
1880
59
2
Poly
C
7.8
0.8
FF
MMCC
Un- identifie dLime
2
NC
2592
73
0
8.5
1.9
FF
SM
CC
Tahiti lime
3NC
108
7755
7
M ono
PG
6.3
1.4
FSSMCD
Le monLemon
4NNo fruit
FSSMCD5
LC
3364645M ono
PG
8.4
1.4SM
MMCC6L
C37585918
M ono
PG
8.2
1.6SM
MMCC
7LC
386566
13PolyPG
8.1
1.6SM
MMCC
PapedaPapeda (Purrut)
8LC
2465
56
4
7.8
1.2
SM
MMCC
9L
No fruit
SMMMCC
10L
No fruit
SMMMCC
Abbreviations, wL=Large, M=M edium, S= Small, N=Without wing, xC =With convex, N=Without convex, y PG= Pale green, C= Cream, G=Green, NG=Nile green,zS pec ies classification based on Swingle (1967).

Table 3. Characteristics of leaves and fruits of citrus collected on Falalop Island in Ulithi Atoll of the FSM

NoFruitEm bryoIsozyme genotype
Species assumed byStylarx
SeedAcidity
endWeight
Shape
FleshBrixyNumber Em bryony(%)
Colour
Got-1
Got-2
Px
M orphology
Isozyme analysis
convex
(g)
index
(%)
1N
No fruit
FSMMDD
Un- identifie d
Un-ide ntif ied
2N
No fruit
FSMMDFUn- identifie d3
LC216160
1
M ono
G
9.2
1.1
SMMMCC
4
LC
286445
6M ono
G
9.2
0.9SM
MMCC
5LC
326865
12
M ono
G
8.21.7SMMMCC
PapedaPapeda (Purrut)
6LC
2062502PolyG8.01.1SMMMCC
7L
No fruit
SMMMCC
8L
No fruit
SMMMCC
9NN
1610480
7Poly
G
7.50.9SMMMDF10N
No fruit
SMMMDF
Calamondin
Calamondin
11
N
No fruit
SM
MMDF
12
S
No fruit
SSMMDD
Sweet ora nge Sweet orange
Abbreviations, wL=Large, M=M edium, S= Small, N=Without wing, xC =With convex, N=Without convex, y PG= Pale green, C= Cream, G=Green, NG=Nile green,zS pec ies classification based on Swingle (1967).

Table 2. Characteristics of leaves and fruits of citrus collected on Mogmog Island in Ulithi Atoll of the FSM

C . hystrix DC.

C . hystrix hybrid

C . hystrix DC.

Species z identified
by m orphology andisozyme analysis
C . aurantifolia hybrid
C . aurantifolia Swing.
C . limon hybrid
C . limon B urm . f.

C . sinensis (L.) Osb.

C . madure nsis Lour.

C . hystrix DC.

C . hystrix hybrid

C . hystrix DC.

Species z identified
by m orphology andisozyme analysis
C . aurantium hybridC . madure nsis hybrid

CLASSIFICATION OF CITRUS SPECIES ON YAP ISLAND AND ULITHI ATOLL OF THE FSM

97w

Le afwing

NoLe afwingwxFruitEm bryo
Isozyme genotype
Species assumed byStylar
SeedAcidity
Weight
Shape
Flesh
end
BrixyColour
Got-1
Got-2
Px
M orphology
Isozyme analysis
Number Em bryony(%)(g)index(%)
convex1
SC
258271
2
M ono
PG
6.6
1.3
FFSMCC
Lime
Tahiti lime
2LC
315455
4
M ono
PG
8.4
1.4SMMMCC
3LC
1559563
M ono
G
8.6
0.8SMMMCC
4L
No fruit
SMMMCC
PapedaPapeda (Purrut)
5L
No fruit
SMMMCC
6L
No fruit
SMMMCC
Abbreviations, wL=Large, M=M edium, S= Small, N=Without wing, xC =With convex, N=Without convex, y PG= Pale green, C= Cream, G=Green, NG=Nile green,zS pec ies classification based on Swingle (1967).

Table 5. Characteristics of leaves and fruits of citrus collected on Fassarai Island in Ulithi Atoll of the FSM

NoxFruit
Em bryoIsozyme genotype
Species assumed byStylar
SeedAcidity
WeightShapeFlesh
end
BrixColoury
Got-1Got-2Px
M orphology
Isozyme analysis
Number Em bryony
(%)
(g)
index
(%)
convex1LC
32555911Poly
G
8.0
1.1
SM
MMCC
PapedaPapeda (Purrut)
2NN
14110
7912
Poly
G
7.71.6SM
MMDF
Calamondin
3N
N
1510675
10
Poly
G
7.8
1.1
SMMMDF
Calamondin
4N
N
8111
73
8
Poly
G
8.3
1.3
SM
MMDF
Lime
Abbreviations, wL=Large, M=M edium, S= Small, N=Without wing, xC =With convex, N=Without convex, y PG= Pale green, C= Cream, G=Green, NG=Nile green,zS pec ies classification based on Swingle (1967).

Table 4. Characteristics of leaves and fruits of citrus collected on Asor Island in Ulithi Atoll of the FSM

C . hystrix DC.

zSpecies identified
by m orphology andisozyme analysis
C . aurantifolia Swing.

C . madure nsis hybrid

C . madure nsis Lour.

z

Species identified
by m orphology andisozyme analysis
C . hystrix DC.

98
T OMINAGA Shigeto, YAMAMOTO Masashi, KOHNO Rumiko, PARK Byoung-Jae, TSUDA Katsuo, O NJO Michio, and ICHITANI Katsuyuki