Asynchronic flowering in self-incompatible annuals

Abstract

Presentation of pollen and stigmas at different times by individuals of a population is likely to exert a profound influence on its genetic structure. We have analysed the changes undergone in (1) asynchrony and (2) single locus heterozygosity, under the irruption of self-incompatible variants in a population of random-mating hermaphroditic annuals. Equations relating genotypic frequencies with time-dependent gamete availability parameters were obtained. These were run in a numerical example over 20 generations, starting from a mixed population showing different degrees of asynchrony depending on the mode of inheritance of this trait. Five cases were analysed, differing in the degree of dominance. Self-incompatibility starts to be expressed in the first generation. Dominance for early- and late-flowering times was negatively associated with asynchrony, due to the existence of self-incompatible variants. A higher degree of potential genetic variability was observed in the locus controlling pollen availability than in the one controlling ovules in advanced generations under this reproductive system. (C) 2000 Annals of Botany Company.