Genetics of self-incompatibility in perennial ryegrass (Lolium perenne L.)

Self-incompatibility (SI) prevents pollination by “self” pollen and promotes outbreeding. SI is a widespread mechanism among angiosperms. Grass SI is known to be controlled by two loci, S and Z, mapped in linkage group 1 and 2 respectively but the mechanism remains elusive. SI in perennial ryegrass (Lolium perenne L.) is studied at the gene level for the S-locus. Using a fine-mapping approach, followed by the sequencing of the genomic S-locus region and the transcripts from pollen and stigma, the project identified four stigma S-candidate genes and potentially six pollen S-candidate genes. Moreover, using closely linked markers, the allelic diversity in a breeding population was assessed for both S and Z. This assay demonstrated that allelic diversity is maintained in a half-sib family recurrent selection programme and that even if the SI genes are unknown, it is possible to predict their genotypes. Finally, self-compatibility has been reported in many grasses. Using self-compatible perennial ryegrass populations, two additional loci, F and T, have been investigated, by a mapping approach as well as observation of self-pollination under the microscope. For both loci, a distortion segregation was observed on linkage group 3 (F) and 5 (T) and initial marker recombination maps were created