DIDYMIUM-IRIDIS MATING SYSTEMS - PARTIAL COMPATIBILITY BETWEEN MATING SERIES

GB 1, a new heterothallic Didymium iridis isolate from England, produces plasmodia when mated to some of the Central American series interbreeding mating types, most of the reproductively isolated Pan 4c clones, and all of the Appalachia series interbreeding mating types. While the hybrids with the Central America and Pan 4c clones usually produced many inviable spores with skewed mating-type segregation ratios, the Appalachian hybrids generally displayed good viability and normal ratios. Although most D. iridis heterothallic isolates have mating-type alleles which are compatible with only a single geographically restricted mating series, the GB 1 isolate is partially compatible with 3 separate series. An additional heterothallic isolate from Florida represents another mating-type series reproductively isolated from previously described series and from GB 1.