Ophiosphaerella Speg., Anal. Mus. nac. B. Aires, Ser. 3 12: 401 (1909).
Index Fungorum number: IF 3612; Facesoffungi number: FoF 00256, 9 morphological species (Species Fungorum, 2022), 5 species with molecular data.
Pathogenic or saprobic on host Sexual morph: Ascomata scattered, solitary, semi-immersed, or erumpent through host tissue with papilla visible as raised, small, black dots on host surface, uniloculate, globose to subglobose, glabrous, dark brown to black, ostiole central, with periphyses, papillate. Peridium thick-walled, composed of hyaline to brown or dark brown, pseudoparenchymatous cells, arranged in a textura angularis. Hamathecium composed of numerous, filamentous, broad cellular pseudoparaphyses, with distinct septa, embedded in mucilaginous matrix, anastomosing at the apex. Asci 8-spored, bitunicate, cylindrical to cylindric-clavate, short pedicellate apically rounded with indistinct ocular chamber. Ascospores fasciculate, lying parallel or spiral, scolecosporous, filiform or filamentous, pale brown to brown, multi-septate, not constricted at the septum, smooth-walled. Asexual morph: see notes (Adapted from Phookamsak et al., 2014).
Type species: Ophiosphaerella graminicola Speg.
Notes: Ophiosphaerella was introduced by Spegazzini (1909) with O. graminicola as type species. Ophiosphaerella is characterized by scattered, solitary, semi-immersed, or erumpent ascomata, cylindrical to cylindric-clavate, short pedicellate asci apically rounded with indistinct ocular chamber, scolecosporous, filiform or filamentous, pale brown to brown, multi-septate ascospores. Spegazzini (1909) rather described a new species of Ophiosphaerella and did not formally introduce the genus. Stafleu et al. (1972) later validly published Ophiosphaerella. Petrak and Sydow (1936) observed the type specimen of Ophiosphaerella and treated Ophiosphaerella graminicola as a synonym of Ophiobolus graminicolus. This treatment was followed by Ainsworth et al. (1971) and von Arx and Müller (1975). Walker (1980) re-studied the type specimen of O. graminicola and suggested the placement of Ophiosphaerella in Pleosporales distinct from Ophiobolus. Ophiosphaerella morphologically resembles Ophiobolus but can be differentiated by absence of central swollen ascospore cells that do not form distinct part spores (Zhang et al., 2012; Phookamsak et al., 2014). Wetzel et al. (1999) first investigated the phylogenetic relationships of Ophiosphaerella and treated the genus as distinct from Phaeosphaeria and other pleosporaceous genera. Several authors accepted Ophiosphaerella in Phaeosphaeriaceae based on multigene phylogenetic analyses (Schoch et al., 2006, 2009; Zhang et al., 2009, 2012; Hyde et al., 2013) but in those studies, only one strain was used (Ophiosphaerella herpotricha CBS 620.86). Phookamsak et al. (2014) used two strains of Ophiosphaerella agrostidis (MFLUCC 11-0152 and MFLUCC 12-0007) and O. herpotricha (CBS 620.86) and suggested that Ophiosphaerella is a polyphyletic genus as O. agrostidis formed a distinct clade from O. herpotricha in Phaeosphaeriaceae. Molecular markers available for Ophiosphaerella include LSU, SSU, ITS, TEF1 and RPB2. Ophiosphaerella is currently a distinct genus in Phaeosphaeriaceae but more taxa with sequence data are needed to confirm the status and taxonomic placement of the genus.
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