Clonal spore population in sporocarps of arbuscular mycorrhizal fungi

Arbuscular mycorrhizal (AM) fungi had been suspected as ancient asexuals because of undiscovered sexual reproductive bodies. However, a recent study on the intra-isolate genetic variation of an AM fungus, Rhizophagus irregularis, suggested two types of nuclear feature in relation with mating type (MAT) locus gene, that is dikaryon with two different putative MAT loci and homokaryon with one putative MAT locus. This result indicated the existence of sexual reproduction life cycle in the AM fungus. We hypothesized that sporocarps of AM fungi might be the sexual reproductive bodies because of the mass spore production. To test this hypothesis, we examined single-nucleotide polymorphisms (SNPs) in the reduced genomic libraries obtained by multiplexed inter-simple sequence repeat genotyping by sequencing (Mig-seq) toward spores isolated from sporocarps of R. irregularis and Diversispora epigaea.