Abstract
Plants have evolved many systems to prevent inappropriate fertilization. Among them, incompatibility is well-organized system, in which pollen germination or pollen tube growth is inhibited in pistils. Self-incompatibility (SI), rejecting self-pollen, promotes outbreeding in flowering plants. On the other hand, inter-species incompatibility, preventing gene flow among species to restrict outbreeding, usually occurs unilaterally, and is known as unilateral incompatibility (UI). In the this study, we characterized novel UI observed between members of the same species, Brassica rapa; pollen of Turkish SI lines was specifically rejected by pistil of Japanese commercial SI variety Osome. The incompatible phenotype of this intra-species UI was closely resembled with that of SI. Segregation analysis revealed that the pollen and stigma factors of this UI were controlled by a single locus, and not linked to the S-locus. These results indicate the existence of novel pollen-pistil recognition mechanism in Brassica.
