Cytospora tanaitica C. Norphanphoun, Bulgakov & K.D. Hyde, sp.
Index Fungorum number: IF551377; Facesoffungi Number: FoF01021; Fig. 3
Etymology: The specific epithet Tanaitica refers to the traditional ancient Greek name ‘Tanais’ of Don River and Lower Don region (modern Rostov region of Russia) in which the fungus was first collected.
Holotype: MFLU 14–0790

Pathogenic and saprobic on branches. Sexual morph: Undetermined. Asexual morph: Stromata 2 – 3-locule in a stroma, semi – immersed in bark, ovoid to elongate ovoid. Locule composed of numerous interconnecting chambers arranged radially or irregularly within a continuous mass of ectostromatic tissue, one conidiomata per one locule. Conidiomata 500 – 1000 μm diam. pycnidial, solitary, immersed, unilocular, dark brown, with an ostiole. Pycnidial wall 30 – 80 μm, consists with brown to dark brown, multilayered of brown, forming a textura angularis cell, with inner most layer thin, hyaline. Conidiophore reduced to conidiogenous cells. Conidiogenous cells blastic, enteroblastic phialidic, hyaline, smooth, formed from the inner most layer of pycnidium wall. Conidia (3–) 3.5 – 4 × 0.6 – 0.7 (−1) μm (x̄ = 3.4×0.7 μm, n = 30) unicellular, allantoid to subcylindrical, hyaline, 1 – celled, aseptate, smooth – walled.

Culture characteristics: Colonies on PDA growing, reaching 7 cm diam. after 11 days at 25 °C, later produce dense mycelium, circular, rough margin gray to dark green, after 5 days, flat or effused on the surface, without aerial mycelium.

Material examined: RUSSIA, Rostov region, Shakhty City, Central Park, on dead branches of Betula pubescens Ehrh. var. glabrata Wahlenb. (syn. Betula borysthenica Klokov, Betulaceae) in culture, 5 May 2014, T. Bulgakov (MFLU 14–0790, holotype; isotype PDD); ex-type living culture, MFLUCC 14–1057, KUMCC.

Notes: Based on phylogenetic analyses and morphological comparison, our isolate belongs to the genus Cytospora in Valsaceae. Cytospora tanaitica has multi – loculate conidiomata with a single ostiole and shares common walls, and is similar to C. sacculus (Schwein.) Gvrit. on Juglans regia L. in conidia size (4.2 × 1 μm) (Fan et al. 2015). However phylogenetic analysis, using ITS sequence data (Fig. 1) show that Cytospora tanaitica can clearly be distinguished from C. gutnerae Gvrit., C. sacculus (Schwein.) Gvrit. and C. terebinthi Bres. Combined analysis of ITS, LSU, β – tubulin and ACT sequence data groups C. tanaitica in a separate clade from these taxa (Fig. 2).

Fig. 1 Phylogenetic tree based on an alignment of the sequences of the ITS regions of Cytospora, Leucostoma, and Valsa species, generated using the MP, ML and Bayesian posterior probabilities (PP) in PAUP. Numbers separated by a slash (or below and above branches) represent MP and ML bootstrap values >50 %. Thickened branches represent Bayesian posterior probabilities (PP) above 95 % are given at the nodes (MP/PP/ML). The tree is rooted in outgroup taxon Phomopsis vaccinii (ATCC 18451). The species obtained in this study are shown in bold.

Fig. 2 Maximum Parsimony (MP) majority rule consensus tree for the analyzed Cytospora isolates based on a combined dataset of ITS, LSU, β-tubulin and ACT sequence data. MP and ML bootstrap support values higher than 50 % and Bayesian posterior probabilities (PP) above 95 % are given at the nodes (MP/PP/ML). The tree is rooted with Phomopsis vaccinii (ATCC18451). The strain numbers are mentioned after the species names. New strains are in blue bold and ex-type strains are in black bold.

Fig. 3 Cytospora tanaitica (holotype) a Stromatal habit in wood b Fruiting bodies on substrate c Surface of fruiting bodies d Cross section of the stroma showing locules, median longitudinal section show locules with independent walls, ostiolar necks converging into a discrete ostiole, and locules surrounded by stroma tissue e Peridium f Apex of conidiomata g Conidiogenous cells h Conidia i Germinating spore. Scale bars: a = 2 mm, b = 1 mm, c – d = 400 μm, e = 30 μm,  f= 200 μm, g – h = 10 μm, I = 20 μm.