UNIPARENTAL MITOCHONDRIAL TRANSMISSION IN THE CULTIVATED BUTTON MUSHROOM, AGARICUS-BISPORUS

A uniparental mitochondrial (mt) transmission pattern has been previou sly observed in laboratory matings of the cultivated mushroom Agaricus bisporus on petri dishes. In this study, four sets of specific mating s were further examined by taking mycelial plugs from the confluent zo ne of mated homokaryons and inoculating these plugs into rye grain for laboratory fruiting and for fruiting under industrial conditions. Exa mination of the mt genotype of each individual fruit body for mt-speci fic restriction fragment length polymorphisms further confirmed that t he mt genome was inherited uniparentally. The vegetative radial growth and the fruiting activity of two pairs of intraspecific heterokaryons , each pair carrying the same combination of nuclear genomes but diffe rent mt genotypes, were compared. Our results suggested that the mt ge notype did not appreciably affect radial growth or fruiting activity. The failure to recover both heterokaryons, each carrying either parent al mt genotype in any given cross, therefore clearly indicated that in matings of A. bisporus, the mt genome from one of the parental homoka ryons is either selectively excluded in the newly formed heterokaryon or selectively eliminated in the immediate heterokaryotic mitotic prog eny of the newly formed heterokaryon.