Compatibility and stability of diploids inCoprinus lagopus

Abstract

Artificially selected diploids ofCoprinus lagopuswhen mated in compatible combinations, either together or with haploids, produce dikaryotic mycelia which are typical of normal haploid-haploid dikaryons. In a diploid-haploid dikaryon, the diploid nucleus is not as stable as when alone in a monokaryon but it can persist through repeated sub-culturing into a fruiting body and eventually through meiosis into the basidiospores. In a diploid–diploid dikaryon either one or the other nucleus becomes haploid so that fruiting bodies with two diploid nuclei are never formed. This fact constitutes a restriction on diploidy in nature and a useful method of reducing diploids to the haploid state.Matings that might be considered to be incompatible at theBmating gene show a significant difference which is related to the number ofBalleles common to the mating colonies. Matings with oneBallele in common, e.g.B3B6+B2B3produce fully compatible and normal dikaryons. Matings with twoBalleles in common, e.g.B3B6+B3B6have, at first while the diploid nuclei still persist, the appearance of an incompatible commonBhaploid heterokaryon. This indicates that theBincompatibility system is based not on a complementary action between differentBalleles but on an oppositional action between the same alleles neutralizing theBgene product which is necessary for dikaryon formation.