Diddensiella caesifluorescens gen. nov., sp. nov., a riboflavin-producing yeast species of the family Trichomonascaceae.

Four strains of a novel heterothallic yeast species were isolated from rotten wood collected in or near the Pilis Mountains in Hungary. The strains produced riboflavin in liquid culture. Analysis of gene sequences for the D1/D2 domains of the LSU nuclear rRNA, as well as analysis of concatenated gene sequences for the D1/D2 nuclear LSU rRNA, mitochondrial SSU rRNA and cytochrome oxidase II placed the novel species in a small clade including only two recognized species, Candida santjacobensis and Candida transvaalensis, in the family Trichomonascaceae. DNA sequence analyses demonstrated that the novel species was distinct from all currently recognized teleomorphic yeast genera. The name Diddensiella caesifluorescens gen nov., sp. nov. is proposed to accommodate the novel genus and species. The new genus proposed here can be recognized only from gene sequence analysis, because the characters of its asexual reproduction and ascospore formation are shared by several members of the genera Trichomonascus, Sugiyamaella and Spencermartinsiella. The type and isotype strains of D. caesifluorescens are NCAIM Y.01949(T) ( = NRRL Y-48781(T) = CBS 12613(T)) and NCAIM Y.01956(I) ( = NRRL Y-48782(I) = CBS 12614(I)), respectively. In view of their close relatedness to D. caesifluorescens, C. santjacobensis and C. transvaalensis are transferred to the genus Diddensiella as new combinations in accordance with changes in the International Code of Nomenclature for algae, fungi and plants.