Roussoella siamensis Phookamsak, 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 : 18-20

Roussoella siamensis Phookamsak, J.K. Liu & K.D. Hyde. , sp. nov. FIG. 11

Index Fungorum : IF550665

Etymology. Named after the country from where the fungus was collected, Thailand (formerly known as Siam).

Saprobic on decaying bamboo culms. Ascostromata 130–150 μm high, 600–750 μm diam, immersed under a clypeus,

FIGURE. Roussoella siamensis . a. Ascostromata on host surface; b. Section through uniloculat; c. Section through peridium ; d. Pseudoparaphyses; e. Young ascus stained by cotton blue; f−g. Ascus; h. Ocular chamber stained by cotton blue; i. Ascospore germination; j. Ascospores; k−n. Ascospore; o−p. Culture characteristics. ─ Scale bars: a = 1 mm; b = 200 μm; c−g = 20 μm; i, j = 10 μm; h, k−n = 5 μm.

visible as raised, shield-shaped or dome–shaped on host surface, uni to multi locules. Locules 65–120 μm high, 127.5– 345 μm diam, lenticularis or shield-shaped with a flattened base, coriaceous, solitary to clustered, gregarious, brown to dark brown, centrally ostiolate. Peridium 7–13 μm wide, composed of several layers of cells of textura angularis, thick-walled, brown to dark brown. Hamathecium comprising 1.5–2 μm wide, numerous, anastomosing, broadly cellular pseudoparaphyses, branching at the apex, smooth-walled, non-constrict at the septum, and embedded in a gelatinous matrix. Asci (65–)73–85(–94) × (6–)7–8μm (x = 78 × 7.5 μm, n = 25), 8–spored, bitunicate, cylindrical, short to long foot-like pedicellate, apically rounded with indistinct ocular chamber. Ascospores (8–)10–12(–14) × 4–5μm (x = 11 × 4.5 μm, n = 30), uni-seriate or overlapping, ellipsoidal to fusiform, 2-celled, constricted at the septum, brown to dark brown, rough-walled, longitudinally ribbed. Ascospores germinated within 12 hours, initially from one cell, hyaline hyphae. Asexual morph did not form in the culture.

Specimen examined THAILAND, Chiang Rai Province, Muang District, Mae Fah Luang University campus grounds, on dead branch of Bambusa , 13 August 2010, R . Phookamsak, RP 0065 (holotype MFLU 11−0185 , ex-type living culture MFLUCC 11−0149 ) .

Notes: Roussoella siamensis is most similar to R. neopustulans , and it is hard to separate them based on morphological characters. However they are phylogenetically distinct from each other in all the phylogenetic reconstructions. Therefore, we describe this fungus as a new species.