New basidiomycetous yeasts from southern Africa. III. Sporobolomyces phyllomatis sp. nov. (Sporobolomycetaceae)

Expanding world of ballistosporous yeasts: Distribution in the phyllosphere, systematics and phylogeny

Ecological and systematic aspects of ballistosporous yeasts inhabiting the phyllosphere of the Asia-Pacific region were reviewed in the light of recent advances. In the past 20 years, the extensive isolation studies of ballistosporous yeasts were carried out in the Asia-Pacific region, and the following new species were found in the phyllosphere of the main island of Japan, of the Ogasawara Islands in the Pacific Ocean, and of Thailand, New Zealand, and the Yunnan Province of China: Bensingtonia ingoldii, B. intermedia, B. miscanthi, B. naganoensis, B. musae, B. sakaguchii, B. subrosea, B. thailandica, and B. yamatoana; Bullera boninensis, B. coprosmaensis, B. hannae, B. huiaensis, B. miyagiana, B. mrakii, B. oryzae, B. penniseticola, B. pseudoalba, B. schimicola, B. sinensis, B. unica, B. variabilis, and B. waltii; Kockovaella imperatae, K. machilophila, K. phaffii, K. sacchari, K. schimae, and K. thailandica; Sporobolomyces blumeae, S. coprosmae, S. coprosmicola, S. dimmenae, S. draycophyllus, S. falcatus, S. griseoflavus, S. inositophilus, S. lactophilus, S. linderae, S. novazealandicus, S. nylandii, S. oryzicola, S. poonsookiae, S. ruber, S. sasicola, S. subbrunneus, S. taupoensis, S. vermiculatus, S. xanthus, and S. yunnanensis; and Udeniomyces megalosporus. Yeast species containing Q-10(H(2)), a monohydrated ubiquinone, have long been considered to be rare yeasts; however, these yeasts were proved to be common in the tropical and subtropical phyllosphere of Asia. The chemotaxonomic and molecular phylogenetic studies based on the sequence analysis of 18S rDNA revealed the heterogeneity of ballistosporous yeasts, which comprised species with polyphyletic phylogenetic origins. A new phylogenetic cluster, Subbrunneus, was newly found in the class Urediniomycetes as the fifth phylogenetical cluster of this class, based on the analysis of 18S rDNA sequences. The Subbrunneus cluster comprises four ballistosporous yeast species found in the phyllosphere of Japan and New Zealand. The future perspectives of basidiomycetous yeast systematics are discussed.

The expanding realm of ballistosporous yeasts

The recent progress in the systematics of ballistosporous yeasts is discussed. The extensive isolation studies carried out in the last decade resulted in a marked increase in the number of ballistosporous yeast species which now number nearly fifty. The increased number of species has expanded the complexity of taxonomic properties in the following ways: expansion of the range of mol% G+C of nuclear DNA to 39-68.5, thus overlapping that of all basidiomycetous yeasts; increased complexity of conidiogenesis with the finding of the genera Ballistosporomyces and Kockovaella. Based on partial sequencing of 18S ribosomal RNA (positions 1451-1618 in Saccharomyces cerevisiae), it is suggested that mode of conidiogenesis has little value for defining genera. Consequently, ballistosporous yeasts merely represent the "ballistosporous stage" of various taxa which cover the whole evolutionary spectrum of basidiomycetous yeasts. The importance of continuing isolation of ballistosporous yeasts is stressed, which together with molecular studies, will aid further progress in the systematics of basidiomycetous yeasts.