MITOCHONDRIAL-DNA VARIATION IN NATURAL-POPULATIONS OF THE MUSHROOM AGARICUS-BISPORUS

We investigated the patterns of mitochondrial DNA variation in the glo bal population of the commercial mushroom Agaricus bisporus. Through t he analysis of RFLP's among 441 isolates from nine countries in North America and Eurasia, we found a total of 140 mtDNA haplotypes. Based o n population genetic analysis, there are four genetically distinct nat ural populations in this species, found in coastal California, desert California, France and Alberta (Canada). While 134 of the 140 mtDNA ha plotypes were unique to single geographical regions, two mtDNA haploty pes, mt001 and mt002, were found in almost every population surveyed. These two mtDNA haplotypes also predominate among cultivars used throu ghout the world for at least the last two decades. These two mtDNA hap lotypes are more similar to the cosmopolitan groups of mtDNA haplotype s than to the indigeneous clusters of mtDNA haplotypes from the two Ca lifornian regions.