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 genetic diversity

Agaricus bisporus is known from field collections in several parts of southern Canada and the border states of Washington and Idaho. In Ontario, the species is associated with urban horticultural sites, agricultural areas, and thoroughfares. In British Columbia, Washington, and Idaho, the species is less well documented but occurs in habitats similar to those in Ontario. All studied isolates from these two regions were genotypically similar to those collected in Europe and also to a representative sample of cultivar isolates believed to be of European origin. In contrast, a population from forests of Picea in the Rocky Mountains of Alberta had genotypes that are very different from European and cultivar groups, including the putatively introduced populations in other parts of Canada. To a lesser extent, the Albertan individuals also differed from three other isolated natural populations, two in California and one in Israel. Two of 35 isolates from Alberta had nuclear genotypes that were partially or entirely consistent with European ancestry, indicating that foreign (probably cultivar) germ plasm has become established in the native habitat. Thirty of 35 isolates from the Alberta field sample had one of six mitochondrial DNA (mtDNA) haplotypes known only from Alberta; the remaining five had an mtDNA type known from cultivar strains. However, nuclear genotypic similarity to other Albertan or European-cultivar isolates was not significantly correlated with presence or absence of this latter mtDNA type. The genetic diversity represented by the previously unknown Albertan population, and to a lesser extent by the heirloom varietal lineages and their derivatives that have become established in Ontario, British Columbia, Washington, and Idaho, is an important resource for breeders of this valuable fungal crop species. Threats to resource populations of this species, and possible responses, are discussed.