Rhodotorula tropicalis sp. nov., a novel red yeast of the order Sporidiobolales isolated from Thailand, Indonesia and Japan

Six yeast strains, representing a novel anamorphic species of the genus <i>Rhodotorula</i>, were investigated in this study. Among them, three strains, SU21, SU16 and SU14, were obtained from three different fruiting bodies of wild mushrooms in Thailand. One strain (ISM36-1) was isolated from soil in Japan, and two strains were isolated from soil (14Y315) and leaf litter (Y15Kr055) collected in Indonesia. Analysis of the sequences of the D1/D2 domain of the large subunit (LSU) rRNA gene and the internal transcribed spacer (ITS) regions showed that the six strains were identical or differed by only one nt substitution in both the D1/D2 domain of the LSU rRNA gene and the ITS regions. <i>Rhodotorula paludigena</i> CBS 6566^T was the most closely related species but with 23-24 nt substitutions in the D1/D2 domain of the LSU rRNA gene and 38-39 nt substitutions in the ITS regions. Phylogenetic analysis based on the concatenated sequences of the ITS regions and D1/D2 domain showed that these strains represent a single species of the <i>Rhodotorula</i> clade that is distinct from other recognized species of the genus. Based on the phylogenetic analysis and phenotypic characteristics, these six strains were assigned to a novel species of the genus <i>Rhodotorula</i>, although sexual reproduction was not observed. The name, <i>Rhodotorula tropicalis</i> sp. nov., is proposed to accommodate the six strains. The holotype is TBRC 14874^T and the ex-type culture is PYCC 8913 (=SU21). The MycoBank number of the novel species is MB 856795.