Roussoella verrucispora Kaz. Tanaka, J.K. Liu & K.D. Hyde., 2014

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 : 20-22

Roussoella verrucispora Kaz. Tanaka, J.K. Liu & K.D. Hyde. , sp. nov. FIG. 13

Index Fungorum : IF550667

Etymology. Named for the verrucose ascospores.

Saprobic on decaying bamboo culms. Ascostromata 1.3–4.8 mm diam., semi-immersed or immersed under a clypeus, raised, visible as black, dome-shape areas on host surface, scattered to gregarious. Locules 280–320 µm high, 400–430 µm diam., depressed globose with a flattened base, 2–3 grouped, ostiolate. Beak short papillate, 50–75 µm high, 55–75 µm wide. Peridium 12.5–17.5 µm thick at sides, composed of 4–6 layers of rectangular flattened cells (3.5–18 × 1.5–4.5 µm), surrounded by wedge-shaped stromatic region (210–240 µm wide at sides) composed of polygonal to subglobose cells (3.5–18 × 4–15 µm). Hamathecium comprising 1–2 µm wide, numerous, anastomosing, cellular pseudoparaphyses, branching, rough-walled, and embedded in a gelatinous matrix. Asci 135–160 × 8–10 µm (x = 150 × 9 µm, n = 18), 8-spored, bitunicate, cylindrical, short-stalked (12–20 µm long). Ascospores 18–24.5 × 5.5–7 µm (x = 21.5 × 6.2 µm, n = 50), uniseriate, fusiform to ellipsoidal, 2-celled, constricted at the septum, brown, verrucose wall, covered with irregular longitudinal short striations and surrounded by an entire sheath of 1–5 µm wide.

Specimen examined. JAPAN, Aomori, Shimokita, Yagen , on twigs of Sasa kurilensis , 18 Nov 2001, Y . Ooki et al. (holotype HHUF 26988 , ex-type living culture CBS 125434 ) .

FIGURE. Roussoella thailandica . a. Ascostromata on the bamboo culm; b. Section of ascostroma; c, d. Peridium ; e. Pseudoparaphyses; f−j. Asci; k, l. Ascospores with irregular longitudinal striations; m. Geminating ascospore; n, o. Culture characteristics. ─ Scale bars: a = 500 μm; b = 100 μm; c, d = 50 μm; e−m = 10 μm; n, o = 30 mm.

FIGURE. Roussoella verrucispora (HHUF 26988). a, b. Ascostromata on host surface; c, d. Section of ascostroma; e. Wedge-shaped stromatic region; f. Peridium ; g. Pseudoparaphyses; h, i. Asci; j–p. Ascospores. ─ Scale bars: a, b = 1 mm; c = 500 µm; d = 100 µm; e–i = 20 µm; j–p = 5 µm.

Notes: Roussoella verrucispora is similar to R. hysterioides , but the asci and ascospores are considerably smaller (asci 135–160 × 8–10 µm vs. 140–210 × 8–11 µm; ascospores 18–24.5 × 5.5–7 µm vs. 18–34 × 6–8 µm) than those of R. hysterioides ( Hyde et al. 1996) . In addition, the ornamentation of ascospores in R. verrucispora is verrucose, while those of R. hysterioides are linear and full length. This species was named as “ R. hysterioides ” (HHUF 26988) in Tanaka et al. (2009). Roussoella verrucispora is also morphologically similar to R. japanensis , but differs in having slightly larger asci and ascospores (asci 135–160 × 8–10 µm vs. 107–132 × 8–9.5 µm; ascospores 18–24.5 × 5.5–7 µm vs. 16–22 × 5.5–7 µm). The ascospores of R. verrucispora have verrucose ornamentation, while those of R. japanensis are striate. Phylogenetic analysis also distinguished these species (FIGS. 1, 2).