Alternation of nuclear phase in the filamentous basidiomycete, Helicobasidium mompa

Abstract

Variation in the number of nuclei and cellular ploidy were observed in eight strains of Helicobasidium mompa. The basidiospores, single-spore isolates and field-isolated strains were all dikaryons. The cellular ploidy, which was assessed by analyzing the fluorescence emitted by DAPI-stained nuclei, was unstable: monokaryotic strains derived from the original dikaryotic strains by successive subcultures were mainly tetraploid, although the original dikaryon was in most cases diploid. On the other hand, a dikaryotic strain derived by treatment with benomyl was haploid. These results suggest that diploid dikaryon is a normal nuclear phase of H. mompa in nature, and the alternation of ploidy may be due to a feature of the mating system of this fungus.