GENETICS OF FRUIT BODY PRODUCTION IN HIGHER BASIDIOMYCETES .1. MONOKARYOTIC FRUITING AND ITS CORRELATION WITH DIKARYOTIC FRUITING IN POLYPORUS-CILIATUS

In P. ciliatus (Polyporaceae) dikaryotic fruiting is controlled by the tetrapolar mechanism of homogenic incompatibility. The occurrence of subunits of the mating type factors A and B, known in other Holobasidiomycetidae, could not be proved. If subunits are present, their distance must be less than 0.2 map units. Monokaryotic fruiting occurs in a strictly haploid phase. Neither karyogamy nor meiosis is required in the fruit bodies for the development of basidia having 2 spores. Genetic analysis has revealed that for the initiation of monokaryotic fruiting a single gene (fi+/fi) is responsible. Additional genes control the shape of the fruit bodies (fb+/fb) and its fertility (mod+/mod). Monokaryotic fruiting is closely correlated with dikaryotic fruiting in 2 ways. The B factors, part of the controlling system for dikaryotic fruiting, block monokaryotic fruiting when both partners are heterogenic for the B factor. Despite the fact that monokaryotic fruiting is suppressed in a dikaryon, the fi gene controls the formation of dikaryotic fruit bodies. The allele fi+ enhances fruit body production, whereas the allele fi may inhibit fruit body production completely. The action and interaction of the incompatibility factors, the genes responsible for monokaryotic fruiting and the genes causing heterogenic incompatibility are discussed with respect to evolution and concerted breeding of mushrooms.