Identification and characterization of a polymorphic receptor kinase gene linked to the self-incompatibility locus of Arabidopsis lyrata

We study the segregation of variants of a putative self-incompatibility gen e in Arabidopsis lyrata. This gene encodes a sequence that is homologous to the protein encoded by the SRK gene involved in self-incompatibility in Br assica species. We show by diallel pollinations of plants in several full-s ib families that seven different sequences of the gene in A. lyrata are lin ked to different S-alleles, and segregation analysis in further sibships sh ows that four other sequences behave as allelic to these. The family data o n incompatibility provide evidence for dominance classes among the S-allele s, as expected for a sporophytic SI system. We observe no division into pol len-dominant and pollen-recessive classes of alleles as has been found in B rassica, but our alleles fall into at least three dominance classes in both pollen and stigma expression. The diversify among sequences of the A. lyra ta putative S-alleles is greater than among the published Brassica SRK sequ ences, and, unlike Brassica, the alleles do not cluster into groups with si milar dominance.