Interspecific hybridization between vigna angularis(wild.) ohwi & ohashi and vigna umbellata(thunb.) ohwi & ohashi through in vitro culture of embryos

Interspecific crosses between adzuki bean(Vigna angularis) and rice bean(V.umbellata) were made with six adzuki bean cultivars and five rice bean lines in order to determine the barriers to hybridization, and to assess the possibility of overcoming the barriers. There was apparently no pre-zygotic barrier between the two species as shown by normal pod set from the crosses in both directions. The pods, however, dried prematurely at early or later stage of development. Hybrid plants were secured in vitro culture of embryos from all the genotypic cross combinations of the two species, but only when rice bean was used as female parents. The F₁ plants were highly fertile to produce normal viable seeds from self pollination. Crossability of the interspecific derivatives with different local cultivars or lines of adzuki bean or rice bean clearly demonstrated that the major reproductive barrier between the species is the physiological post-zygotic embryo abortion and further genetic barriers, if present, may not be strong enough to completely restrict gene flow over species. Therfore, once hybrid plants secured by embryo culture, it would be highly possible to incorporate the desired characteristics of rice bean into adzuki bean cultivars by conventional breeding procedures.