GENUS SKELETOCUTIS (POLYPORACEAE) IN THE UKRAINIAN LEFT BANK FOREST STEPPE

Upon review of the reference data and the author's herbarium specimens were recorded five species of the Skeletocutis genus in the Ukrainian Left Bank Forest Steppe. One species, S. brevispora, is a new record for Ukraine, another one, S. carneogrisea, was found for the first time in the Ukrainian Left Bank Forest Steppe. For other two species, S. nivea, S. subincarnata, new localities were found within the studied region.

Both in Ukraine and globally, most of Skeletocutis species are saprotrophes on the dead wood of various conifers and broadleaved trees. Such species cause white rot. Some of them are able to develop on basidiocarps of the other polypores [21,22].
According to the data base Index Fungorum (request, dated April 24, 2017), Skeletocutis genus comprises 43 species. Fungi of this genus are widely distributed in the Northern Hemisphere. Twenty of them are known in Europe [7,21] and only six species have been recorded in Ukraine [2][3][4][5][6]. According to the reference data, prior to our research there had been three species known for the Left Bank Forest Steppe: Skeletocutis nivea (Jungh.) Jean Keller, S. odora (Peck ex Saccardo) Ginns, S. subincarnata (Peck) Jean Keller. All of them were found in Kharkiv Oblast [4][5][6].

Materials and Methods
Among materials applied for this article there were species of aphyllophoroid fungi collected in June-October, 2016 at the forestlands of Ichnia National Natural Park (Ichnia Rayon, Chernihiv Oblast). The Natural Park's area in terms of mycofloristic zoning of Ukraine belongs to the Left Bank Forest Steppe [1].
The micromorphological structures of the specimens were examined in a 5% aqueous potassium hydroxide solution and Melzer's reagent. The nomenclature of the species follows the "MycoBank" database [http://www.mycobank.org/quicksearch.aspx].

Results and Discussion
Upon review of the herbarium specimens collected over the specified area, we have reported 4 species belonging to Skeletocutis genus. Among them, one species (Skeletocutis brevispora Niemelä) is new for Ukraine, another one (Skeletocutis carneogrisea A. David) was found rare for our country and the new one for the Forest Steppe, for two species (Skeletocutis nivea (Jungh.) Jean Keller, Skeletocutis subincarnata (Peck) Jean Keller) the new locations were found in the Left Bank Forest Steppe. Generally, according to the reference data and the author's own gatherings, as of the date, five species of fungi belonging to this genus have been known for the Left Bank Forest Steppe. The comparative features of these species are shown in table 1. Basidiocarps annual, resupinate, 1-2 mm thick, waxy when fresh and firm-ceraceous after drying. Pore surface at first white, later straw-to lemon-yellowish, pores angular at first 6-9 per mm. Margin initially pruinose-byssoid, white, later lacking or very narrow. Subiculum very thin, whitish. Hyphal system dimitic: skeletal hyphae slightly thick-walled, dominating in all parts of basidiocarps, 3-4 µm wide, swelling up to 5-5,5 µm wide in KOH (but not dissolving); generative hyphae thin-walled, with clamps, 3-3,5 µm wide, at the dissepiment edges slightly encrusted. Cystidia none, bottle-shaped cystidioles with sharp apices present in the hymenium, 10-13×4-5,5 µm. Basidia short-clavate 10-12×4-4,5 µm, with a basal clamp. Basidiospores 3,4-4,1×1,2-1,5 µm, cylindrical to slightly allantoid tapering towards the apiculus, without guttules. Ecological peculiarities: It develops over basidiocarps of Phellinidium ferrugineofuscum (P. Karst.) Fiasson & Niemelä. T. Niemelä in the species description specifies that it develops on such substrate so often that such feature may be applied for the species identification [19]. According to L. Ryvarden and I. Melo, S. brevispora is able to develop on the wood of conifer species affected by Ph. ferrugineofuscum [21].
S. brevispora is deemed a rare species, however, locally it may be found rather often [19,22]. Globally, it is known in certain countries of Europe (Norway, Sweden, Final [21], Poland [14], in the European part of Russia [16,22] and in China [11].
It is new for Ukraine.