Cytospora curvata Norphanphoun, Bulgakov, T.C. Wen & K.D. Hyde, sp. nov., Index Fungorum number: IF 552602

Etymology: The specific epithet “curvata” refers to the conidia character (Latin ‘curvata’ means ‘crooked’, ‘bent’, ‘curved’).

Holotype: MFLU 15-2229

Associated with twigs and branches of Salix alba L. Sexual morph: Undetermined. Asexual morph: Conidiomata 900–1100 × 470–580 μm diameter, semi-immersed in host tissue, scattered, erumpent, unilocular, with ostiolar neck. Ostioles 140–160 μm, same level as the disc surface. Peridium comprising a few to several layers of cells of textura angularis, with inner most layer thin, 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 (5.4–)5.8–7.7 ×1.2–1.3(–1.4) μm (x̅ = 5.9 × 1.3 μm, n = 30), unicellular, elongate-allantoid, slightly curved, hyaline, smooth-walled.

Distribution: Donskoye forest, Krasnosulinsky District, Rostov Region, Russia.

Host: On dead and dying branches of Salix alba.

Culture characteristics – Colonies on MEA, reaching 8 cm diameter after 7 days at 25 °C, producing dense mycelium, circular, white, margin rough, lacking aerial mycelium.

Material examined: RUSSIA, Rostov Region, Krasnosulinsky District, Donskoye Forest, shore of little pond, on dead and dying branches of Salix alba (Salicaceae), 28 June 2015, T. Bulgakov, T-525 (MFLU 15-2229, holotype, KUN, isotype), ex-type living culture, MFLUCC 15-0865, KUMCC.

Notes: Phylogenetic analysis of combined ITS, LSU, RPB2 and ACT sequence data indicate that Cytospora curvata (MFLUCC 15-0865) forms a separate branch as a sister taxon to C. rusanovii (MFLUCC 15-0853, MFLUCC 15-0854).

FIG. Cytospora curvata on Salix alba (MFLU 15-2229, 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 Ostioles. 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, c = 500 μm, d = 200 μm, e = 50 μm, f = 100 μm, g, j, k = 10 μm, h, i = 5 μm.