XVI International Botanical Congess

In the grasses, gametophytic self-incompatibility is controlled by two unlinked genes, S and Z. Phalaris coerulescens provides a good model system for self-incompatibility in the grasses as an extensive collection of lines of defined S and Z genotype are available, and several of pollen only and complete mutants have been produced. A putative S gene was previously identified and shown to encode a novel thioredoxin protein. However, recent results indicate that this is unlikely to be the S gene but it does appear to represent a gene closely linked to S. The thioredoxin is believed to play a role in the stigma-pollen reaction but not in the recognition process. Attempts to isolate the S and Z genes have now focussed on fine linkage mapping of the loci in Phalaris. At present markers have been identified that lie within 1cM of each gene.