Five genes determining intersterility in Heterobasidion annosum

Previous studies of Heterobasidion annosum have shown the existence of two intersterility groups (biological species) designated "S" and "P." Nearly complete intersterility exists between Finnish representatives of the two groups; however, a significant degree of interfertility exists between North American "S" and "P" groups. Analyses of progeny from laboratory crosses of North American representatives of the "S" and "P" groups identified five genes that specify intersterile and interfertile mating reactions. Segregation of alleles was observed for four of the five genes, linkage analysis was performed, and a model for the interaction of these genes is proposed. The genetic basis of biological species in higher fungi is discussed.