Roussoella nitidula Sacc. & Paol., Atti Ist.

Liu, Jian-Kui, Phookamsak, Rungtiwa, Dai, Dong-Qin, Tanaka, Kazuaki, Jones, Gareth, Xu, Jian-Chu, Chukeatirote, Ekachai & Hyde, Kevin D., 2014, Roussoellaceae, a new pleosporalean family to accommodate the genera Neoroussoella gen. nov., Roussoella and Roussoellopsis, Phytotaxa 181 (1), pp. 1-33 : 9-11

Roussoella nitidula Sacc. & Paol., Atti Ist. Veneto Sci., 6: 410. 1888. FIGS 3, 4

Saprobic on decaying bamboo culms or palms branches. Ascostromata 0.3–0.5 mm high, 1.5–2.4 mm diam, immersed under a clypeus, raised, visible as black dome-shaped on host surface, multilocular, solitary to gregarious, coriaceous. Locules 150–300 μm high, 240–720 μm diam, subglobose to lenticular or quadrilateral to dome-shaped, clustered, black, ostiolate. Peridium 10–21 μm wide, composed of several layers of cells of textura angularis to prismatica, thickwalled, brown to dark brown. Hamathecium comprising 1.5–2 μm wide, numerous, anastomosing, narrowly cellular pseudoparaphyses, branching at the apex, smooth-walled, and embedded in a gelatinous matrix. Asci (87–)110–150(–200) × (8–)9–10(–11) μm (x = 122 × 9.8 μm, n = 30), 8-spored, bitunicate, cylindrical, short pedicellate, apically rounded with an ocular chamber. Ascospores (15–)16–18(–19) × (5.5–)6–7 μm (x = 17 × 6.5 μm, n = 30), uni-seriate, ellipsoidal to fusiform, 2-celled, constricted at the septum, initially pale brown, becoming brown to dark brown, rough-walled, at maturity with longitudinally ribbed. Ascospores germinated within 12 hours, initially from one cell, hyaline hyphae. Asexual morph produced on bamboo pieces on WA cultures after 2 months. Conidiomata 620–760 µm high, 865–1000 µm diam, superficial, visible as black slimy on hyphae which covered the bamboo pieces, pycnidium, globose or dome-shaped, thickened the basal of pycnidium, solitary, scattered or gregarious, indistinctly ostiolate. Pycnidial wall 13–80 µm wide, composed of several layers of cells of textura intricata, dark brown to black. Conidiophores arising from the basal cavity around conidiomata, unbranched or branched, 2–3 septa. Conidiogenous cells (2.5–)6–11(–16) × (1.5–)2–2.5(–3) µm (x = 8.5 × 2.5 μm, n = 10), phialidic, integrated, cylindrical or cylindric-clavate or irregular swollen cell, hyaline, 1−2-septate, smooth-walled. Conidia (6–)7–8 × 3–4 μm (x = 7.5 × 3.5 μm, n = 30), oblong to ellipsoidal, initially hyaline, becoming brown to yellowish brown, aseptate with two guttules, thick-walled, roughwalled, verrucose.

Specimens examined MALAYSIA, Malacca, on culms of Bambusa, 1885 , B . Scortechini ( PAD 2484 , holotype) ; THAILAND, Chiang Rai, Muang District, Khun Korn Waterfall , on dead culms of Bambusa . 17 Dec. 2010, R . Phookamsak , RP0098 ( MFLU 11-0218 , epitype designated here), ex-epitype living culture MFLUCC 11-0182 ; THAILAND, Uttaradit Province, on dead culms of Bambusa . 02 Nov. 2011, D. Q . Dai , DDQ218 ( MFLU 13-0642 ), culture MFLUCC 11-0634 ).

Notes: The type material of Roussoella nitidula was examined, and two fresh collections (on culms of Bambusa from Thailand) were observed and isolated. They have superficial morphological similarities, such as black domeshaped ascostromata; hypha-like, septate, numerous, narrow pseudoparaphyses; cylindrical, relatively thin-walled asci and two-celled dark brown ornamented ascospores. In addition, the size of asci and ascospores are similar, except the asci and ascospores in type material of R. nitidula are slightly larger than the fresh collections (asci 123–220 × 7–11 µm vs. 110–200 × 8–11 μm; ascospores 17.5–21 × 5.5–8 µm vs. 16–19 × 5.5–7 μm). Although there is a small variation between these fresh collections and the type material of R. nitidula , we consider them to represent one species and epitype the type of Roussoella ( R. nitidula ) in this study. The isolated strain R. nitidula (MFLUCC 11‒0182) formed the Cytoplea asexual morph in culture; it is similar with C. hysterioides (asexual morph of Roussoella hysterioides ) as described by Hyde et al. (1996), but differ in having smaller conidia (7–8 × 3–4 μm vs. 7–10(–13) × 4–5(–6) μm).

FIGURE. Roussoella nitidula (MFLU 11−0218) a. Ascostromata on host surface; b. vertical section through ascostromata; c. section through peridium ; d. Pseudoparaphyses; e−g.Asci. h−k.Ascospores; l. Germinating ascospore; m. Conidiomata on bamboo pieces on WA; n. Section through conidioma; o,p. Conidiophores; q−t. Conidia ; u−v. Cultures characteristics. ─ Scale bars: b = 500 µm; n = 200 µm; c−h, l, o = 20 µm; q = 10 µm; i−k, p, r−t = 5 µm.

FIGURE. Roussoella nitidula (from PAD 2484, holotype). a. Appearance of the ascostromata on host surface; b. Asci and pseudoparaphyses; c. Ascospores with longitudinal striations; d. Pseudoparaphyses; e−g. Asci; h−k. Ascospores; ─ Scale Bars: a = 3 mm; b = 60 µm; c, d = 10 µm; e−g = 30 µm; h−k = 10 µm.