INDIGENOUS AND INTRODUCED POPULATIONS OF AGARICUS-BISPORUS, THE CULTIVATED BUTTON MUSHROOM, IN EASTERN AND WESTERN CANADA - IMPLICATIONS FOR POPULATION BIOLOGY, RESOURCE-MANAGEMENT, AND CONSERVATION OF GENETICDIVERSITY

Agaricus bisporus is known from field collections in several parts of southern Canada and the border states of Washington and Idaho. In Onta rio, the species is associated with urban horticultural sites, agricul tural areas, and thoroughfares. In British Columbia, Washington, and I daho, the species is less well documented but occurs in habitats simil ar to those in Ontario. All studied isolates from these two regions we re genotypically similar to those collected in Europe and also to a re presentative sample of cultivar isolates believed to be of European or igin. In contrast, a population from forests of Picea in the Rocky Mou ntains of Alberta had genotypes that are very different from European and cultivar groups, including the putatively introduced populations i n other parts of Canada. To a lesser extent, the Albertan individuals also differed from three other isolated natural populations, two in Ca lifornia and one in Israel. Two of 35 isolates from Alberta had nuclea r genotypes that were partially or entirely consistent with European a ncestry, indicating that foreign (probably cultivar) germ plasm has be come established in the native habitat. Thirty of 35 isolates from the Alberta field sample had one of six mitochondrial DNA (mtDNA) haploty pes known only from Alberta; the remaining five had an mtDNA type know n from cultivar strains. However, nuclear genotypic similarity to othe r Albertan or European-cultivar isolates was not significantly correla ted with presence or absence of this latter mtDNA type. The genetic di versity represented by the previously unknown Albertan population, and to a lesser extent by the heirloom varietal lineages and their deriva tives that have become established in Ontario, British Columbia, Washi ngton, and Idaho, is an important resource for breeders of this valuab le fungal crop species. Threats to resource populations of this specie s, and possible responses, are discussed.