Vigna umbellata (Thunb.) Ohwi & Ohashi

[Rice bean]


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<The situation in Japan and information from the NIAS genebank>
According to the literature, rice bean was grown in the southwestern part of Japan formerly (Noda 1951). It was called "Me-naga (long eye)" in Tsushima island and "Sasage or Kaninome" in Goto island in Nagasaki prefecture, "Kani-no-me (eye of a crab)" in Yamaguchi prefecture, "Baka-azuki (foolish azuki bean)" in Kagoshima prefecture, and "Kage-azuki (shady azuki bean)" in Tottori prefecture (Noda. 1951, Nakayama and Bhatti. 1995, Fukuoka et al.1995, Tomooka, 1996). Recently, cultivation of this crop has nearly disappeared in Japan. A total of 15,536 MT of rice bean was imported in 1991 as a substitute of azuki bean mainly from Thailand (12,938 MT) and Myanmar (1,700 MT) (Zatsumame Yunyu Kikin Kyokai.1995).

It is described that the cultivation is popular in Southeast Asia and Pacific islands (Duke 1981). However, rice bean is not very popular in Thailand. It was only sporadically sold in the market in Thailand. Commercial rice bean production for exportation started in 1960s in and around Loei province in northeast Thailand (Arwooth 1982).In Chiang Rai market in northern Thailand, immature pods are briefly boiled with salt and sold. They say that this is one of the traditional ways of eating rice bean among hill tribes.

Rice bean is considered to have been domesticated in Southeast Asia. Wild forms of rice bean is distributed in Northeastern India, Burma, Thailand, Laos and Vietnam (Ohashi et al. 1988).

Rice bean is an annual food legume belonging to the subgenus Ceratotropis in the genus Vigna. The genus Vigna, together with the closely related genus Phaseolus, forms a coplex taxonomic group, called Phaseolus-Vigna complex. Verdcourt (1970) proposed a very restricted concept of Phaseolus, limiting it exclusively to those American species with a tightly coiled style and pollen grains lacking course reticulation, hence, promoting significantly the concept of Vigna. According to his proposal, rice bean and its relatives (which is now recognized as the subgenus Ceratotropis) were transferred to the genus Vigna from the genus Phaseolus. Marechal et al. (1978) followed Verdcourt and presented a monograph on the Phaseolus-Vigna complex. Their taxonomic system is generally accepted now.

In their monograph, two varieties are recognized in V.umbellata. One is V.umbellata var.umbellata which is rice bean, and another is V.umbellata var.gracilis which is a wild ancestor of rice bean. On the other hand, Tateishi (1985) considered that the specimen of V.umbellata var.gracilis described in the monograph of Marechal et al.(1978) should be included in V.minima. 2n=22.

Generally, morphology of rice bean is similar to azuki bean. Seed is slender and hilum is protruding. Flower color is golden yellow. Pod attaches to the peduncle downward.

Dry seed is boiled and eaten with rice. It is also used to make sweets.

Arwooth N.L.1982. Agronomic aspects of grain legumes farming. In "Grain legumes production in Asia" pp.247-260.

Duke,J.A. 1981. Handbook of legumes of world economic importance. Plenum Press, New York.

Fukuoka,S., M.M.C.Manawaprema and K.Okuno. 1995. Exploration for Genetic Resources of Cereals and Food Legumes on Goto Islands, Nagasaki Prefecture. Annual Report on Exploration and Introduction of Plant Genetic Resources. Vol.11:21-26. (in Japanese with English summary)

Nakayama,H. and M.S.Bhatti.1995. Exploration for Crop Landraces on Tsushima Island, Nagasaki Prefecture. Annual Report on Exploration and Introduction of Plant Genetic Resources. Vol.11: 11-20. (in Japanese with English summary)

Noda,A. 1951. Studies on Native (Primitive) Varieties of Crop Plant : Observations on a Climbing Variety of Adsuki Bean Native to San'in District, Japan (1). Japan J. Crop Sci. 21(2): 134-135. (in Japanese with English Sammary).

Ohashi,H., Y.Tateishi, T.Nemoto and Y.Endo. 1988. Taxonomic studies on the Leguminosae of Taiwan III. Sci. Rep. Tohoku Univ. 4th ser. (Biology) 39: 191-248. p.245-246.

Tateishi,Y. 1985. A revision of the Azuki bean group, the subgenus Ceratotropis of the genus Vigna (Leguminosae). Ph.D. Thesis, Tohoku University, Sendai, Japan.

Tomooka,N. 1996. Collection and Field Study on Landraces of Cultivated Crops in Kagoshima Prefecture. Annual Report on Exploration and Introduction of Plant Genetic Resources. Vol.12: 9-19. (in Japanese with English summary)

Zatsumame Yunyu Kikin Kyokai. 1995. Yunyu Mamerui Zukan (A pictorial book of imported food legumes) (in Japanese).