THE MOLECULAR PHYLOGENY OF THE ASCOMYCETOUS ANAMORPHIC YEAST GENUS ARXULA VAN DER WALT, SMITH ET YAMADA BASED ON THE PARTIAL SEQUENCES OF 18S AND 26S RIBOSOMAL RIBONUCLEIC ACIDS

Abstract

Nine strains of Arxula, Stephanoascus, Endomyces, Yarrowia, Dipodascus, and Geotrichum were examined regarding the partial sequences of 18S and 26S rRNAs. In the positions 471 through 627 of 26S rRNA, the two strains examined of the genera Arxula and Stephanoascus had 99% and 98% maximum homologies, respectively. The two species of the genus Arxula, A. terrestris and A. adeninivorans had 80% maximum homology. The maximum homologies were 81-84% between the genera Arxula and Stephanoascus. Arxula, Endomyces, Yarrowia, Dipodascus, Geotrichum, and Saccharomyces species constituted their own clusters at 49-76% maximum homologies. In the positions 1685 through 1835 of 26S rRNA, the two strains examined of the genera Arxula and Stephanoascus had 2 and 0 base difference, respectively. The two species of the genus Arxula had 7-9 base differences. The base differences were 4-8 between the genera Arxula and Stephanoascus. Arxula, Endomyces, Yarrowia, Dipodascus, Geotrichum, and Saccharomyces species constituted their own clusters at 13-25 base differences. In the positions 1451 through 1618 of 18S rRNA, the two strains examined of the genera Arxula and Stephanoascus had no base difference. The two species of the genus Arxula had 2 base differences. The base differences were 2-4 between the genera Arxula and Stephanoascus. Arxula, Endomyces, Yarrowia, Dipodascus, Geotrichum, and Saccharomyces species constituted their own clusters at 5-9 base differences. The data obtained are discussed from the taxonomic and phylogenetic points of view.