CONICET | Buscador de Institutos y Recursos Humanos

The teleomorphic basidiomycetous species Leucosporidium scottii has a multiple allelic sexual incompatibility system and is closely related to the anamorphic species Leucosporidiella creatinivora and Le. yakutica. In the present work, the phenotypic, genetic and sexual characteristics of 12 new wild isolates (from Antarctica and Patagonia Argentina) and 18 collection strains of the three species were studied. Physiological comparisons showed few discrepancies which were reduced to a variable differential assimilation of L-rhamnose, D-galactose and cadaverine. MCP-PCR fingerprinting suggested a preliminary three species aggregation. However, phylogenetic analysis of rRNA genes sequences (D1D2+ITS) did not give a clear differentiation of the species and revealed the existence of at least 4 clades, which did not differed in more than 3 bp in D1/D2 and 4 bp in ITS. Sexual compatibility studies (ca. 900 crossed), showed the production of mycelium and teliospores (including germinated ones) among strains of the three species. None of the strains crossed with the sister species Le. muscorum, Le. fragaria and L. golubevii. Phylogenetic analysis using sequences from the MT pheromone receptor alleles (STE3.A1 or STE3.A2) was able to differentiate the three species and occurrence of either of the two alleles was in perfect agreement with sexual compatibility results. From the results obtained here, it became clear that yeasts assigned to L. scottii, Le. creatinivora and Le. yakutica are a group of very closely related teleomorphic and interbreeding strains. Although genetic delimitation is possible for the three species, the differences observed between them are lower than that expected for species that have ended the speciation process. The concept of Leucosporidium scotti species-complex is proposed for this group of species until additional data are gathered and definitive taxonomical decisions are made.