Cytospora paratranslucens Norphanphoun, Bulgakov, T.C. Wen & K.D. Hyde, sp. nov.,
Index Fungorum number: IF552608

Etymology: The specific epithet is composed from Greek prefix ‘para-’ meaning ‘near’ or ‘beside’ and Latin ‘translucens’ is from the species name, in reference to the occurrence on Cytospora.

Holotype: MFLU 15-1986

Associated with twigs and branches of Populus alba L. Sexual morph: Undetermined. Asexual morph: Conidiomata 450–550 × 270–350 μm diameter, semi-immersed in host tissue, scattered, erumpent, breaking through the outer branch, multiloculate, with ostiolar neck. Ostioles 70–150 μm diameter, at same level as the disc surface. Peridium comprising a few to several layers of cells of textura angularis, with inner most layer thin, red-brown, outer later dark brown to black. Conidiophores unbranched, reduced to conidiogenous cells. Conidiogenous cells blastic, enteroblastic, phialidic, formed from the inner most layer of pycnidial wall, hyaline, smooth-walled. Conidia (5.5–)6.5–7.3 × 1.3–1.5(–1.8) μm (x̅ = 6.8 × 1.6 μm, n = 30), unicellular, allantoid, slightly curved, hyaline, smooth-walled.

Culture characteristics: Colonies on MEA, reaching 8.5 cm diameter after 7 days at 25 °C, producing dense mycelium, circular, margin rough, white, with aerial mycelium.

Material examined: RUSSIA, Rostov Region, Shakhty City, Grushevka steppe slopes near Grushevsky pond, riparian grove, on dead and dying branches of Populus alba, 14 May 2015, T. Bulgakov, T-282 (MFLU 15-1986, holotype, PDD, isotype), ex-type living culture, MFLUCC 16-0506, KUMCC; RUSSIA, Rostov Region, Krasnosulinsky District, Donskoye forestry, lining-out nursery, trees and shrubs, dying twigs and branches on Populus alba L. var. bolleana (Lauche) Otto, 27 October 2015, T. Bulgakov, T-1016 (MFLU 15-3678, PDD), living culture, MFLUCC 16-0627, KUMCC.

Notes: Cytospora species associated with Populus have been reported worldwide. In this study, five novel species are introduced, which were collected from Populus viz. C. melnikii, C. parakantschavelii, C. paratranslucens, C. rusanovii and C. salicacearum. Cytospora paratranslucens is most similar to C. germanica and C. nivea (Adams et al. 2006). However, they can be distinguished by conidia size (6.8 × 1.6 versus 5 × 1, 6–7.5 × 1.2 μm respectively) (Adams et al. 2006). Furthermore, C. paratranslucens has multiloculate conidiomata sharing a single ostiole, while C. germanica and C. nivea have multiloculate conidiomata with individual or compressed ostioles in the conidiostromata.

In the ITS phylogenetic analyses, Cytospora paratranslucens groups with C. translucens Sacc. (138-2 and 35) with high bootstrap support (94% ML/ 1.00 PP). ITS sequence data is only available for C. translucens in GenBank. Therefore, we compare morphology of C. paratranslucens and C. translucens, from the original description in Saccardo (1884). Cytospora paratranslucens can be distinguished from C. translucens in having multiloculate conidiomata, while in C. translucens they are uniloculate. The conidia of C. paratranslucens are larger than those of C. translucens (6.8 × 1.6 μm versus 4.6 × 1.2 μm).

FIG: Cytospora paratranslucens on Populus alba (MFLU 15-1986, holotype). a Stromatal habit in wood. b Fruiting bodies on substrate. c Surface of fruiting bodies. d Cross section of the stroma showing conidiomata. e Peridium. f Ostiolar neck. g–i Conidiogenous cells with attached conidia. j Mature conidia. k Germinating spore. l, m Colonies on MEA (l-from above, m-from below). Scale bars: a = 2000 μm, b = 1000 μm, c = 1000 μm, d = 200 μm, e = 20 μm, f = 100 μm, g, h, i, j = 5 μm, k = 10 μm.