The production and behaviour of diploids ofCoprinus lagopus

Abstract

Diploid strains ofCoprinus lagopushave been synthesized from commonAheterokaryons either as oidial colonies or sectors. The criteria of growth rate and colony morphology on selective medium were used to distinguish between diploid and heterokaryon colonies. The average oidial size and hyphal width of diploid strains was significantly greater than that of the haploid parental strains.Diploid monokaryons were very stable and only rarely produced haploid segregants. However, aneuploid intermediates in haploidization have been identified and these segregated further to give haploid monokaryons with recombinant genomes.Dikaryons formed from diploid and haploid strains produced fruiting bodies. Meiosis and basidiospore production were irregular owing to the formation of triploid or partially triploid fusion nuclei in the basidia. In contrast to their stability in monokaryons, diploid nuclei tended to be unstable when combined in a dikaryon with a haploid nucleus, and often underwent partial haploidization before fruiting. Segregation of genes in the basidiospore progeny reflected whether haploidization had occurred before or after the formation of the fruiting body. If the haploid nucleus had aBmating-type allele common to the diploid nucleus, haploidization effected loss of the common allele.