Interspecific hybridization between rice bean (Vigna umbellata) and its wild relative (V. minima): fertility-sterility relationships

Abstract

The pre-and post-fertilization barriers in the interspecific crosses between Vigna umbellata and V. minima were investigated. In the reciprocal crosses (V. minima as the ♂ parent) the entry of pollen tubes into the ovary was delayed by about 4 h, and no seed set was observed. However, no pre-fertilization barriers were encountered in crosses involving V. minima as the ♀ parent and V. umbellata as the ♂ parent (normal cross). The delay/absence of divisions in the endosperm and the failure of embryo to divide were the post-fertilization barriers responsible for somatoplastic sterility in normal crosses which yielded a few hybrid seeds. The hybrid seeds showed poor germinability. The F₁ hybrids were intermediate between the parents in most morphological characters, and are completely sterile for pollen. Backcrossing of F₁ hybrid with both the parents did not restore fertility in the progenies. V. minima is considered as the tertiary gene pool of the rice bean.