Compatibility and stability of diploids in Coprinus lagopus

Abstract

Artificially selected diploids of Coprinus lagopus when 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 the B mating gene show a significant difference which is related to the number of B alleles common to the mating colonies. Matings with one B allele in common, e.g. B₃B₆+B₂B₃ produce fully compatible and normal dikaryons. Matings with two B alleles in common, e.g. B₃B₆+B₃B₆ have, at first while the diploid nuclei still persist, the appearance of an incompatible common B haploid heterokaryon. This indicates that the B incompatibility system is based not on a complementary action between different B alleles but on an oppositional action between the same alleles neutralizing the B gene product which is necessary for dikaryon formation.