Fungalpedia – Note 2469, Roussoella
Roussoella Sacc.
Citation when using this data: Dong W et al. 2020 – Fungalpedia, Ascomycota.
Index Fungorum, Facesoffungi, MycoBank, GenBank, Fig. 1
Classification: Roussoellaceae, Pleosporales, Pleosporomycetidae, Dothideomycetes, Pezizomycotina, Ascomycota, Fungi
Saprobic on various flowering plants in terrestrial or submerged wood in freshwater habitats, mainly on bamboo and palms. Sexual morph: Ascostromata solitary to gregarious, visible as black, raised, elongate to hemisphaerical or dome-shaped ascostroma, uni- to multi-loculate, glabrous, coriaceous. Locules clustered, immersed under a clypeus, subglobose to lenticular or quadrilateral dome-shaped, central ostiolate, with a minute papilla. Peridium slightly thick at the side, composed of several layers of flattened, brown to dark brown pseudoparenchymatous cells, arranged in textura angularis to textura prismatica. Pseudoparaphyses dense, trabeculate, filamentous, hyaline, branching at the apex, anastomosing, embedded in a gelatinous matrix. Asci 8-spored, bitunicate, cylindrical to cylindric-clavate, short pedicellate, with obtuse to knob-like pedicel, apically rounded with well-developed ocular chamber. Ascospores overlapping uni-seriate, ellipsoidal to fusiform, pale brown to dark brown, 1-septate, ornamented, with or without a mucilaginous sheath (Liu et al. 2014). Asexual morph: Coelomycetous, reported as Cytoplea (Hyde et al. 1996a). Conidiomata pycnidial, scattered to clustered, solitary to gregarious, semi-immersed to superficial, globose to subglobose, dark brown to black, single- or multi-loculate, locules separated by dark, palisade-like cells. Peridium slightly thick at the base, composed of several layers of brown to dark brown, pseudoparenchymatous cells, arranged in textura angularis to textura prismatica. Conidiophores arising from the basal cavity, reduced to conidiogenous cells. Conidiogenous cells enteroblastic, phialalidic, determinate, discrete, ampulliform, hyaline, smooth-walled. Conidia globose to subglobose, oblong or ellipsoidal, brown, aseptate or septate, smooth- or rough-walled.
Notes: Roussoella was introduced by Saccardo and Paoletti (1888) with R. nitidula as the type species. An epitype of R. nitidula was designated by Liu et al. (2014) who also found the Cytoplea asexual morph in culture. Roussoella accommodates species having large ascostromata with multi-loculate, bitunicate asci and brown, fusiform to ellipsoidal, ornamented, didymosporous ascospores which are mostly associated with bamboo and palms (Tanaka et al. 2009; Hyde et al. 2013; Liu et al. 2014; Dai et al. 2017; Jiang et al. 2019).
Type species: Roussoella nitidula Sacc. & Paol.
Other accepted species: Species Fungorum – search Roussoella.
Figure 1 – Roussoella aquatica (MFLU 18-1169, holotype). a Conidiomata on host substrate. b Conidiomata cut through vertically. c Vertical section of conidioma. d Structure of peridium. e Conidiogenous cells bearing conidia. f–i Conidia. j Germinated conidium. k Colony on PDA (from front). Scale bars: c = 50 μm, d, j = 20 μm, e = 5 μm, f = 10 μm, g–i = 3 μm.
References
Entry by
Wei Dong, Faculty of Agriculture and Food, Kunming University of Science and Technology, Kunming 650500, China, Department of Entomology and Plant Pathology, Faculty of Agriculture, Chiang Mai University, Chiang Mai 50200, Thailand, Innovative Agriculture Research Center, Faculty of Agriculture, Chiang Mai University, Chiang Mai 50200, Thailand, Center of Excellence in Fungal Research, Mae Fah Luang University, Chiang Rai 57100, Thailand, Institute of Plant Health, Zhongkai University of Agriculture and Engineering, Haizhu District, Guangzhou 510225, China
Published online 15 May 2026