PARTIAL INTERSTERILITY IN HETEROBASIDION-ANNOSUM

Interfertility among European and North American strains of Heterobasidion annosum was examined in hetero- x homokaryon pairings with testers of known intersterility group affiliation. In a set of 164 heterokaryotic strains, approximately 10% interfertility was found between the Scandinavian S and P groups. Twelve percent of European S group strains were partially interfertile with North American P group tester strains and 16% of European P group strains were interfertile with North American S group tester strains. Homokaryotic European F group strains were highly interfertile with the North American S group.