Effects of Self‐ and Cross‐Compatibility on the Frequency of Hybrids in Medicago sativa L.1

Abstract

The influence of self‐ and cross‐compatibility of both parents on seed production potential and the percentage of crossed seed in. hybrids was studied. In separate studies a wide range in self‐ and cross‐compatibility of seven white flowered clones used as pistillate parents was found. Self‐ and cross‐compatibility were closely associated. In separate studies four of the five purple flowered clones used as male parents were rated as very low in selffertility. Cross‐compatibility as males of the five purple flowered clones varied; however, none rated high in crosscompatibility. In crosses between white flowered and purple flowered clones, pods per flower and seed per flower declined rapidly as self‐compatibility of the female parent decreased. Selection for low self‐compatibility resulted in low seed yield regardless of mating pattern. Pod and seed production were also influenced by the level of male cross‐compatibility of the male parent. The percentage of crossed seed in the hybrids was not closely associated with self‐compatibility of the female parent. Male cross‐compatibility was associated with the percentage of crossed seed in the hybrids. Specific combinations yielded 100% crossed seed, while other combinations within the same levels of self‐ and cross‐compatibilities yielded 0% crossed seed. A type of “specific combining ability” for the production of hybrids was suggested.