Relationship between monokaryotic growth rate and mating type in the edible basidiomycete Pleurotus ostreatus

The edible fungus Pleurotus ostreatus (oyster mushroom) is an industrially produced heterothallic homobasidiomycete whose mating is controlled by a bi factorial tetrapolar genetic system. Two mating loci (matA and matB) contro l different steps of hyphal fusion, nuclear migration, and nuclear sorting during the onset and progress of the dikaryotic growth. Previous studies ha ve shown that the segregation of the alleles present at the matB locus diff ers from that expected for a single locus because (i) new nonparental B all eles appeared in the progeny and (ii) there was a distortion in the segrega tion of the genomic regions close to this mating locus. In this study, we p ursued these observations by using a genetic approach based on the identifi cation of molecular markers linked to the matB locus that allowed us to dis sect it into two genetically linked subunits (matB alpha and matB beta) and to correlate the presence of specific matB alpha and matA alleles with dif ferences in monokaryotic growth rate. The availability of these molecular m arkers and the mating type dependence of growth rate in monokaryons can be helpful for marker-assisted selection of fast-growing monokaryons to be use d in the construction of dikaryons able to colonize the substrate faster th an the competitors responsible for reductions in the industrial yield of th is fungus.