Meredithblackwellia eburnea gen. et sp. nov., Kriegeriaceae fam. nov. and Kriegeriales ord. nov.--toward resolving higher-level classification in Microbotryomycetes.

A field survey of ballistosporic yeasts in a Neotropical forest yielded a new species isolated from a fern leaf. The isolate is a cream-colored butyrous yeast that reproduces by budding. Budding occurs at both the apical and basal cell poles; occasionally multiple budding events co-occur, giving rise to rosette-like clusters of cells at both poles of the yeast mother cell. DNA sequences of large and small subunit and the internal transcribed spacer regions of the nuclear ribosomal DNA cistron indicated an affinity to Microbotryomycetes, Pucciniomycotina. A new genus, Meredithblackwellia, is proposed to accommodate the new species, M. eburnea (type strain MCA4105). Based on phylogenetic analyses, Meredithblackwellia is related to Kriegeria eriophori, a sedge parasite, to an aquatic fungus Camptobasidium hydrophilum and to several recently described anamorphic yeasts that have been isolated from plant material or psychrophilic environments. Morphological and ultrastructural studies confirm the relatedness of M. eburnea to these taxa and prompted the re-evaluation of higher-level classification within Microbotryomycetes. We propose here a new order, Kriegeriales, and place two families, Kriegeriaceae fam. nov. and Camptobasidiaceae R.T. Moore, within it. Our study re-emphasizes the need for systematic revision of species described in Rhodotorula.