The phylogenetic relationship of the genera Phaffia Miller,Yoneyama et Soneda and cryptococcus Kuetzing emend. Phaff et Spencer (Cryptococcaceae) based on the partial sequences of 18S and 26S ribosomal ribonucleic acids.

Abstract

The partial sequences of 18S and 26S rRNAs were studied in eighteen strains of Phaffia, Cryptococcus, Candida, and Filobasidiella species. The positions determined were 1451 through 1618 (168 bases) of 18S rRNA, and 492 through 625 (134 bases), and 1686 through 1835 (150 bases) of 26S rRNA. These three determinations showed that the genus Cryptococcus is phylogenetically heterogeneous: the maximum homologies of 26S rRNA were 65-94% in the positions 492 through 625 and 69-93% in the positions 1686 through 1835, and the base differences of 18S rRNA were 0-13 in the positions 1451 through 1618. Filobasidiella neoformans, a teleomorph of the genus Cryptococcus, had partial sequences somewhat different from the species examined of the genus Cryptococcus (maximum homologies, 74-84% and 74-86%; base differences, 4-12, respectively). Candida humicola was included in the cluster of the genus Cryptococcus. However, the base differences of the species were not so small (maximum homologies, 69-77% and 72-84%; base differences, 5-13). The genus Phaffia constituted its own cluster separate from the species of Cryptococcus, Candida, and Filobasidiella (maximum homologies, 61-70% and 71-85%; base differences, 6-16, respectively). So the genus Phaffia is retained as an independent genus.