Genetic evidence for somatic haploidization in developing fruit bodies of Armillaria tabescens

Armillaria spp, have vegetative hyphae with diploid uninucleate cells, but the fruit bodies of many species contain clamped dikaryotic hyphae, Earlier observations suggest that somatic haploidization takes place in developing fruit bodies. To verify this, a uninucleate diploid cell was isolated from each of the 49 mating combinations between single-spore isolates of Armill aria tabescens and they were fruited. Twenty-four isolates produced fruit b odies with at least a partially dikaryotic subhymenium. Dikaryotic hyphae w ere isolated from fruit-body primordia and homokaryons were obtained by mic romanipulation or by protoplasting. Approximately half of the isolates prov ed to represent recombinant mating types in respect to parent homokaryons, and most of them contained recombinant haploid DNA, based on random-amplifi ed microsatellite markers. The results show that the nuclei in dikaryotic h yphae found in fruit bodies result from somatic haploidization. The mechani sm of haploidization remains unclear, (C) 2000 Academic Press.