Investigations into the inter-relationships ofPhaseolus vulgaris L. andP. Coccineus LAM

The crossability ofP. coccineus (self-incompatible) andP. vulgaris (self-compatible) was much higher whenvulgaris was used as the female parent. Reciprocal difference in crossability was due to the retarded development of embryo and endosperm tissue during the immediate post-fertilization period in the crossP. coccineus ×P. vulgaris . Backcrossing the reciprocal F₁ hybrids to the maternal species was more successful than to the paternal species.Two varieties ofP. vulgaris differed significantly in their ability to hybridize with six genotypes ofP. coccineus; this difference was shown to be genetical.The F₁ hybrids were readily distinguishable from the parent species at the seedling stage and could be classified into two distinct morphological types; one group showed and abnormal wrinkling of the leaves. The frequency of the abnormal progeny in the F₁ generation could be satisfactorily explained on the basis of either allelic or genic interaction. The importance of this genetic system in the divergence of the two species is discussed.