New anamorph genus Pseudonadsoniella of dark brown yeast-like fungi similar to the genus Nadsoniella in having very slow growth in culture on all nutrient media but differing in showing better development of ‘colony-like formations’ on Saburo agar medium and potato sections as well as showing a phylogenetic affiliation to the family Meripilaceae (Polyporales, Agaricomycotina) after phylogenetic analysis based on ITS nrDNA sequences is described. The new species Pseudonadsoniella brunnea from Antarctic, Argentina, Galindez Island, is described and illustrated. The position of some species groups appeared to be polyphyletic genera Rigidoporus, Physisporinus and Phaeococcomyces after ITS nrDNA sequences is discussed. Corrections to identification of some specimens of the genera Phlebia, Elmerina, Physisporinus are provided. Nomenclature of Issatschenko’s species Nadsoniella nigra and its two infraspecific taxa as well as type and voucher confusion of these taxa in molecular study of the members of the genus Exophiala is discussed. It is shown that the anamorph fungus Exophiala sp. CBS 546.82 (VKM F-2137 or ‘voucher Ruban’s strain 365’), hitherto incorrectly recorded as Nadsoniella nigra var. hesuelica (nom. inval.), is a taxon still waiting for describing. The conclusion that the original Issatschenko’s collection of Nadsoniella nigra (type strain CBS 535.94) and status of the strain Exophiala sp. CBS 546.82 are in urgent need of the modern revision/re-examination is done.

Influence of essential oils of the following plants Rosmarinum officinalis L., Pinus sibirica Du Tour, Abies sibirica Ledeb., Juniperus communis L., turpentine oil, and polyhexamethyleneguanidine (PHMG) on black yeast-like fungi Exophiala alcalophila FCKU 304 was investigated. Disc-diffusion method was used. Level of the antifungal influence on X. alcalophila found to be different for each chemical. 5% PHMG is characterized by the highest fungicide activity. Level of the antifungal activity of essential oils of plants Rosmarinum officinalis, Pinus sibirica and Abies sibirica is similar to 1.5-3 % PHMG activity. The PHMG and essential oil of Rosmarinum officinalis found to cause exchanges of morphometric indices of cells, colony morphology and intensity of budding E. alcalophila what is considered as adaptations of investigated culture of black yeast-like fungus. Furthermore dimorphic transition 'yeasts – mycelium' of E. alcalophila was observed under influence of essential oil of Rosmarinum officinalis.

Peculiarities of the growth of a dark pigmented yeastlike fungus,Pseudonadsoniella brunnea, on32nutrientmedia(11 solid,3semisolidand18liquidones)arecharacterized.The mostoptimalmediaforthisfungusfoundtobeSaburoagar, Saburo agar with 10 % sucrose solution, original medium with rolled oats, bran and 10 % sucrose solution, pieces of rawpotatowithandwithout10%sucrosesolution,modified glucosepeptoneyeastmedium,peptonewaterwithglucose, beefextract [meat infusion] broth with glucose and gelatin. Acidicmedia(pH=3-4)arethemostoptimalforP. brunnea growth.

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