Cytospora nivea (Hoffm.) Sacc., Michelia 2: 264 (1881)
For other possible synonyms see Index Fungorum (Index Fungorum number: 236471)

Associated with twigs and branches of Salix acutifolia Willd. Sexual morph: Undetermined. Asexual morph: Conidiomata 1000–1300 × 340–380 μm diameter, semi-immersed in host tissue, scattered, erumpent, discoid, circular, with 3–4 locules, ostiolate. Ostioles 100–150 μm diameter, at the same level, with flattened top. Peridium comprising a few to several layers of cells of textura angularis, inner layer thick, brown, outer later dark brown. Conidiophores unbranched, reduced to conidiogenous cells. Conidiogenous cells blastic, enteroblastic, phialidic, formed from the inner most layer of pycnidial wall, hyaline, smooth-walled. Conidia (7.1–)7.4–8.8 × 1.5–1.6(–1.9) μm (x̅ = 7.5 × 1.8 μm, n = 30), unicellular, allantoid, slightly curved ends, hyaline, smooth-walled.

Culture characteristics: Colonies on MEA, reaching 2 cm diameter, after 7 days at 25 °C, producing dense mycelium, circular, margin rough, white, lacking aerial mycelium.

Material examined: RUSSIA, Rostov Region, Ust’-Donestsky District, near Nizhnekundryuchenskaya Village, arenal sandy forest, on dead and dying branches of Salix acutifolia (Salicaceae), 17 August 2015, T. Bulgakov, T-506 (MFLU 15-2210, PDD), living culture, MFLUCC 15-0860, KUMCC.

Notes: Fan et al. (2015b) have reported and illustrated Cytospora nivea (CFCC 89642). The morphology of our fresh collection resembles C. nivea (epitype) in Fan et al. (2015b) in having multiloculate conidiomata, allantoid, slightly curved, hyaline and 7.6 × 1.9 μm conidia and in the combined multi-gene phylogeny. This is the first report of C. nivea from Salix acutifolia in Russia therefore, details are provided for this species to facilitate identification.

FIG: Cytospora nivea on Salix acutifolia (MFLU 15-2210). a Stromatal habit in wood. b Fruiting bodies on substrate. c Surface of fruiting bodies. d Cross section of the stroma showing perithecia. e Peridium. f Ostioles. g–h Conidiogenous cells with intact conidia. i Conidia. j Germinating spore. k, l Colonies on MEA (k-from above, l-from below). Scale bars: a = 2000 μm, b = 500 μm, c, d = 200 μm, e, f = 50 μm, j = 20 μm, g, h, i = 5 μm.