Vigna riukiuensis (Ohwi) Ohwi & Ohashi

To Japanese version

<Taxonomy>

Vigna riukiuensis is a perennial wild species belonging to the subgenus Ceratotropis in the genus Vigna. Tateishi (1984) proposed that this taxon should be treated as a variety of Vigna minima. According to Tateishi (1984), V.minima is very variable species. The leaflets vary from linear to triangular-ovate or ovate. In extreme cases as described under Phaseolus heterohyllus, linear and ovate leaflets appear in the same individual. Therefore, he considered that formae distinguished merely by the shape of the leaflets cannot be adopted as distinct. However, var.minor (Matum.) Tateishi is separated by the orbicular or elliptic leaflets with rounded or obtuse apex. The shape of the leaflets of this variety is apparently correlated to the number of ovules (7-9 against 9-12 in typical V.mimina) and the glossiness of the leaflets.

2n=22

<Distribution>

The distribution of V.riukiuensis is restricted to Taiwan and Okinawa prefecture (the southernmost islands) in Japan (Tateishi, 1984).

<Characteristics>

V.riukiuensis has glossy leaf, which is round and small. Flower color is golden yellow. The seed testa is smooth with dark gray color. Germination is hypogeal. 100 seeds weight is about 1-1.4g

<As genetic resources>

We have conducted several explorations to collect this species on the Ishigaki, Iriomote and Yonaguni islands in Japan (Tomooka et al.,1992, Egawa et al.,1990, 1991). This species is distributed mainly near the sea. V.riukiuensis showed a high level of resistance to bruchid beetles (Tomooka et al. 1992).

<References>

Egawa,Y., D.Siriwardhane, N.Tomooka, K.Tomita and H.Nakano, 1990. Collection of V.riukiuensis and V.reflexo-pilosa, wild relatives of azuki bean on Iriomote island, Okinawa prefecture. Annual Report on Exploration and Introduction of Plant Genetic Resources. Vol.6:23-30.

Egawa,Y., H.Horikoshi, N.Tomooka, and H.Nakano, 1991. Collection of wild relatives of adzuki bean, Vigna riukiuensis and V.reflexo-pilosa, on Yonaguni island, Okinawa prefecture. Annual Report on Exploration and Introduction of Plant Genetic Resources. Vol.7:13-20.

Tateishi,Y. 1984. Contributions to the Genus Vigna (Leguminosae) in Taiwan I. Sci. Rep. Tohoku Univ. 4th ser. (Biology) 38: 335-350.

Tomooka,N., Y.Egawa, C.Lairungreang and C.Thavarasook, 1992. Collection of wild Ceratotropis species on the Nansei Archipelago, Japan and evaluation of bruchid resistance. JARQ, 26:3, 222-230.