The species Blastobotrys navarrensis Sesma and Ramirez was delineated based on the description of the single strain CBS 139.77T. Based on its phenotypic similarities to Blastobotrys proliferans, B. navarrensis CBS 139.77T was later considered a synonym of B. proliferans. In the present study, we isolated the yeast strain IST 508 (=PYCC 8784=CBS 16671) from the soil surrounding an olive tree in Ferreira do Alentejo, Portugal. The phylogenetic analysis of D1/D2 domain and ITS sequences from strain IST 508 indicates that is closely related to B. navarrensis and B. proliferans. Although strain IST 508 differs from B. navarrensis CBS 139.77T by 14 substitutions and 20 indels (6.6 % divergence) in the ITS sequence, no divergence was detected at the level of D1/D2 domain, mitochondrial small subunit rDNA, and cytochrome oxidase II sequences. On the other hand, strains IST 508 and CBS 139.77 differ from B. proliferans NRRL Y-17577T by eight substitutions (1.4 % divergence) in the D1/D2 domain sequence, by 16 substitutions (2.7 % divergence) in the cytochrome oxidase II sequence, and by 16 substitutions (3.7 % divergence) in the mitochondrial small subunit rDNA sequence. Due to the high number of variable phenotypic tests in B. proliferans and B. navarrensis, strains from the two species are difficult to distinguish. Contrasting with what is described for other Blastobotrys species, no differences were detected at the level of micromorphology between the two species. Nevertheless, based on the molecular differences between the two strains, CBS 139.77 and IST 508, and B. proliferans NRRL Y-17577T and their phylogenetic analysis, strains CBS 139.77 and IST 508 are from B. navarrensis and this species should be considered as an independent species and not a later synonym of B. proliferans. We propose an emended description of B. navarrensis.
Keywords: Blastobotrys; Blastobotrys navarrensis; Blastobotrys proliferans; ascomycete yeast; soil microbiology; soil yeast.