Azuki Bean Cultivation in Hokkaido and Breedingat Tokachi Agr. Exp. Station
Shimada Hisanori, Akiko Tazawa, Hitoshi Sato
Bean Breeding Laboratory at Tokachi Agricultural Experiment Station in Hokkaido
Shinsei-Minami 9-2, Memuro-cho, Kasai-gun, Hokkaido 082-0081, Japan

Abstract

Azuki bean is an important upland legume in Japan. It is mainly used in making traditional sweets.
Hokkaido, the northernmost island of Japan, is the main producing area of azuki bean. Azuki beanbreeding is practiced at Tokachi Agr. Exp. Station, Hokkaido mainly for developing the varieties withdisease resistance, cool-weather tolerance and adaptability to mechanized farming.

Introduction

Azuki bean (Vigna angularis ) is a legume of
East Asia. Azuki bean does not demand so high temperature as other leguminous crops in Vigna , such as
Vigna unguiculata , Vigna radiata and so on.
In Japan, azuki bean only with red or creamy
yellow seed coat is sold, although there are various
seed coat colors. The main uses of azuki bean in Japanare “an” paste, sweets called “Wagashi”, and sugarglazed boiled beans called “Amanatto”, that are allsweet. Consumption for these three uses accounts formore than 80 percent. In other words, most of azuki
bean is used as a material of sweet confectioneries inJapan.

Hokkaido is the main producing area of azuki
bean in Japan although it is planted all over Japan asa summer crop for home-consumption. Planted areain Hokkaido in 2007 was 23,800 hectare which wasabout 73 percent of the total planted area in Japan, andproduction in Hokkaido was 58,100 ton, about 89% oftotal production.

Fig 3. Planted area and production of azuki bean inJapan (2007)
In Hokkaido, the growing period of azuki bean
is 100 to 140 days, and the yield is 2.0 to 3.0 ton perhectare. Seed size is 10 to 25 grams per 100 seeds. Theplant type is indeterminate dwarf although there aresome genetic resources with a viny plant type.
Fig 1. Use of azuki bean produced in Hokkaido
Total consumption in Japan has declined slightly. It has been about 80,000 or 90,000 ton for theseseveral years. About 70 percent of that is occupied byproduction in Hokkaido.

Fig 2. Domestic consumption of azuki bean in Japan- 87 -The calendar of azuki bean cultivation in Hokkaido
In Hokkaido seeding time is usually late May.
It takes 10 to 14 days to germinate from seeding. After
germination, farmers operate intertillage several times
including soil piling, and/or manual or mechanicalweeding two or three times before flowering.
Flowering stage of azuki bean continues over along period. It begins in late July and continues untillate August. Farmers generally practice chemical control of diseases and insects two or three times between
flowering and maturity.
Maturing time differs with region. It is normally
early or mid September in the south-west or central
regions of Hokkaido. On the other hand, it is normallylate September or early October in eastern or northern regions, where the temperature during summer islower than the former regions.

Harvesting methods of azuki bean in Hokkaido
1. Traditional laborious method
Cutting at the maturity stage by bean cutters↓ 2 or 3 days, pre-drying on the ground
Gathering and putting up cut plants for drying↓ About a week
Piling up cut plants to a large cluster for drying↓ 10 - 20 days
Threshing
2. Cutting and picking-up system
Cutting at the full-ripe stage by bean cutters↓ 0 or 2 days, pre-drying on the groundThreshing cut plants by a thresher or a combinewith a pickup unit

Pickup thresher

Pickup combine

3. Direct cutting and threshing by a combine after
full-ripe stage - the most labor-saving method

can be controlled.
Some varieties with both BSR and PSR resistance have already been released. BSR resistance is aprerequisite for new azuki bean cultivars to be recommended in Hokkaido.
2. Cool-weather tolerance
Currently the important objective is coolweather tolerance. The eastern part of Hokkaido,
namely Tokachi and Abashiri districts, are criticalareas for azuki bean cropping, because the climate
there is very severe. Although azuki bean is extremely sensitive to frost, the frost-free period is very
short (about 130-140 days) in these areas. Azuki bean
production of these areas has been struck by coolweather damage at an average frequency of once infour years and severe cool-weather occurs once in tenyears (Fig.4). Azuki bean is the most sensitive crop
to low temperature in summer among summer uplandcrops in Hokkaido. Its yield fluctuates up and down
annually being influenced by the climate during thegrowing season. Therefore, cool-weather tolerance isan indispensable breeding objective for azuki bean.

Breeding of Azuki bean in Tokachi Agr. Exp. Station
1. Resistance to soil-borne diseases
The main objectives of azuki bean breeding
for these thirty years have been in corporation of resistance to soil-borne diseases, brown stem rot (BSR)
and Phytophthora stem rot (PSR).
BSR, which is caused by a fungi (Phialophoragregata Allington et Chamberlain), is distributed allover Hokkaido. Hyphae enter vascular bundles disturbing water and nourishment to upper parts of theplant. Therefore, lower leaves begin to wilt in middle or late August. It progresses upward and arriving
at the top before seeds fully mature. So the seeds on
infected plants become smaller than normal and theyield is reduced.
PSR, which is also caused by a kind of fungi(Phytophthora vignae Purss), tends to break out in
hot and wet conditions in summer mainly in the fields
converted from paddy fields located in south-westernand central regions in Hokkaido. In July or August,the rot of the stem surface progresses upward fromthe ground, so diseased plants die.
The test and selection of BSR resistance arepracticed in isolated fields where the disease is severein the Tokachi Agr. Exp. Station. In addition, DNAmarkers for resistance to BSR were developed several years ago. We can efficiently select resistance now.
On the other hand, PSR seldom occurs soseverely in Tokachi District, because of the low temperature in summer. Therefore, the test and selection
are practiced at Kamikawa Agr. Exp. Station in thecentral region of Hokkaido, where the temperature ishigher than Tokachi in the fields where the moisture- 88 -Fig 4. Yield of azuki bean in Tokachi District Note)● indicate the severely damaged year by very
cool summer
Cool-weather damage occurs by low temperature during different growing stages. One of thestages that is sensitive to severe damage is vegetative
stage before the start of flowering. Low temperatureduring this stage disturbs the vegetative growth irreversibly even if high temperature occurs later. Therefore, the size of plants becomes too small for normal
yield (Fig. 5). We have detected difference in susceptibility to low temperature during this stage among
diverse germplasm. We are now selecting less susceptible lines in the field located at a cooler region.
The severest damage by low temperature isobserved during the pollen forming period. Low temperature during this stage disturbs the pollen formation, and consequently flowers are not pollinated. We
have evaluated for low temperature tolerance in thisstage among genetic resources for thirty years, buthave not been able to find promising materials. However, recently, we could detect one promising material by the screening in a phytotron (a glasshouse instill small. Long hypocotyl lines are useful for that
purpose.
For combine harvesting, lodging resistanceand high position of pod setting are important. Heightof pod-setting of long hypocotyl lines naturally becomes higher than normal hypocotyl lines.
Therefore we are trying to select long hypocotyl lines with lodging resistance both for effective weed control and for combine harvesting withless crop loss.
Genetic resources preserved in Tokachi Agr. Exp.
StationWe have collected local genetic resources ofazuki
bean
and wild relative species all over Japan,Fig 5. Difference of cool weather damage by low
in Korea, Taiwan, Nepal, Bhutan and Vietnam sincetemperature during vegetative stage
Left:severely damaged, Right:slightlydamaged 1983. Now we preserve more than 3,500 accessionsof azuki bean and its related species (Fig. 7). Amongwhich the temperature can be controlled low even in these, more than 800 accessions have been tested forsummer). Now we are checking the tolerance of the BSR resistance, and more than 1,100 for PSR resistprogeny lines crossed between the material and some ance. A lot of resistant materials to these two diseases
major varieties.
each have been detected so far. Many BSR or PSR
resistant resources are derived from prefectures other
3. Suitability to machinery cropping
than Hokkaido or Korea. We expect cool-weather tolAnother objective is adaptability to machinery erance among resources derived to be from the highcropping. In Tokachi District, farm size per house- altitude area in Nepal, Bhutan or Vietnam.
hold is increasing accompanied with the reduction offarm households over the last thirty years. There is alabor shortage. In azuki bean cultivation, weed control is the most laborious work, because it has not yet
been mechanized sufficiently. Harvesting is also anoperation that requires mechanization.

Fig.6. A long hupocotyl line in late days in June.
Left : normal line, Right : long hupocotylline.
For mechanization of weed control of azuki
bean, we are trying to develop long hypocotyl lines(Fig 6). Growth in the early growing stage of azuki
bean is so slow that hilling up soil along the azuki
bean row in the early stage buries not only weeds
but also azuki bean plants. Moreover, azuki bean is
so sensitive to herbicides that chemical weed control
risks damaging the plant. If the plant height and location of lower leaves were higher than the present varieties in the early growing stage, farmers would beable to effectively bury weeds on the azuki bean row
without burying azuki bean plants when weeds are- 89 -Fig 7. Origin of genetic resources of azuki bean
preserved at Tokachi Agr. Exp. Station.
Most of these collections have short day photoperiod sensitivity. In Hokkaido the day length is solong in summer that they come to flowering stage aslate as in early September under natural conditions in
the field. At Tokachi Agr. Exp. Station, the first frost
in autumn comes early October on average. Therefore
it is impossible to get mature seeds before frost damage comes. For the seed multiplication, we cultivatethem in pots in summer and keep them warm in thegreenhouse in October, or cultivate them in a heatedgreenhouse in winter under natural short day. These
genetic resources are now stored also at Genetic
Resources Division in Hokkaido Prefectural Central
Agr. Exp. Station or/and National Gene Bank.

As mentioned above, genetic resources from allover Asia have played essential roles in successful azuki
bean breeding programs. We have to preserve worldwide
genetic resources for future international cooperation.
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