Intersterility groups in the Pleurotus ostreatus complex from the continental United States and adjacent Canada

Abstract

Mating compatibility studies using strains from 170 North American collections in the Pleurotus ostreatus complex reveal three intersterile species of oyster mushrooms in the United States and Canada. Initial pairings among monokaryotic single spore isolates were performed to determine the number of intersterile groups. Dikaryon – monokaryon pairings using monokaryotic tester strains were then used to screen additional dikaryotic cultures of the oyster mushroom. Pairings of tester strains from Europe indicate that two European taxa, P. ostreatus and Pleurotus pulmonarius, are also widely distributed in North America. A third intersterility group occurring primarily on aspen in North America was intersterile with all other known species, and is described as a new species, Pleurotus populinus. All three species differ from one another in their morphology, growth characteristics, geographic distributions, and host ranges. Other than mating compatibility tests, however, no single type of character was found to be completely reliable for distinguishing these species in the field or under laboratory conditions. Furthermore, morphological characters used to distinguish European species of the P. ostreatus complex were not useful when applied to corresponding mating-compatible groups from North America. Key words: oyster mushroom, species concept, mating incompatibility.