Kwoniella olivae f.a. sp. nov., a novel basidiomycetous yeast species associated with olive ecosystems

Three yeast strains of the basidiomycetous genus Kwoniella (subphylum Agaricomycotina; class Tremellomycetes; subclass Tremellomycetidae) were isolated from samples of olive oil collected in northern Italy. Analysis of the D1/D2 domains of the 26S rRNA gene (LSU) and of the complete internal transcribed spacer (ITS) region indicated that these strains displayed high sequence similarity to three other strains isolated from insect frass in olive trees in South Africa, suggesting that they are conspecific. Phylogenetic analyses based on LSU and ITS sequences placed these six strains in a well-supported clade closely related to Kwoniella newhampshirensis, Kwoniella shandongensis and Kwoniella lonicerae with sequence divergence of 1.2-1.6% (7-9 nucleotide substitutions) in the D1/D2 domains and 1.8-6.4% (12-37 nucleotide substitutions) in the ITS regions. Based on these results and on phenotypic analyses, a novel species, Kwoniella olivae f.a. sp. nov. PYCC 9971T (=CBS 18666T), is proposed. The MycoBank number is MB 860006.