Genetic modifications of dimorphic incompatibility in the Turnera ulmifolia L. complex (Turneraceae)

Diploid and tetraploid populations of Turnera ulmifolia are distylous and exhibit a strong self-incompatibility system. Distyly is governed by a single locus with two alleles. Several self-compatible variants were, however, obtained and the nature and genetic control of self-compatibility was assessed using controlled crosses. The study documented the occurrence of self-compatible variants in four contrasting situations. These included the following. (i) Self-compatibility in a diploid short-styled variant. The gene(s) governing self-compatibility interact with the distyly locus and are expressed only in short-styled plants. When tetraploids carrying the genes were synthesized, self-incompatibility reappeared. (ii) Self-compatibility occurred in a cross between geographically separate diploid populations. Self-compatibility appeared sporadically in the F1. Crosses revealed that self-compatibility is likely under polygenic control. (iii) Low levels of self-compatibility occurred in a tetraploid population....