Dual mating in Botrytis cinerea

B. cinerea is considered a typical example of a heterothallic fungus which requires two compatible mating types to complete the sexual cycle. Mating occurs between a strain carrying a MAT1-1 locus and a strain carrying a MAT1-2 locus. Having both loci initiates sexual development called apothecia. However, an unusual mating type behaviour was reported of certain B. cinerea strains, referred to as ‘dual mater’, in which a strain carrying a single MAT allele is able to mate both with a MAT1-1 ánd a MAT1-2 reference strain. In this study, we performed crosses of dual mater strain RS11 (carrying a MAT1-2 allele) with the two reference strains and studied the segregation of MAT loci in the progenies by PCR with primers specific for the MAT1-1 (a domain) and MAT1-2 (HMG box domain) locus. The result showed that dual mater strain RS11 is able to cross with the MAT1-2 reference strain (SAS405) and form apothecia. 50 single ascospore progeny were sampled from individual apothecia and all of the progeny contained the MAT1-2 allele. If the dual mating behavior is a monogenic trait, it would be expected to segregate 1:1, where 50% of the progeny would behave as dual mater and the other 50% would act as a standard heterothallic (MAT1-2) isolate. We performed a backcross of 30 single ascospore progeny (all carrying the MAT1-2 allele) to the MAT1-2 reference strain, and 10 out of 30 were able to form apothecia. One of the progeny was even homothallic, i.e. able to form apothecia without fertilization. The mechanism of this phenomenon remains unknown. We are considering sequencing dual mater strains and their progeny (that behave as a dual mater or a homothallic isolate), but we also consider the possibility that this trait is under epigenetic control. RAZAK BIN TERHEM, JAN A.L. VAN KAN