Ophiostoma Syd. & P. Syd., Annls mycol. 17(1): 43 (1919)
Diaporthomycetidae, Ophiostomatales, Ophiostomataceae, Ophiostoma
Saprobic or weak parasites on decaying woody substrates. Sexual morph: Ascomata superficial, perithecial, globose to subglobose, dark brown to black, with long ostiolar neck. Ostiole occasionally comprising two or three necks, long, becoming pale brown to hyaline at the apex, including ostiola hyphae, hyphae pale brown to hyaline, filamentous, septate with an outer layer of thin-walled, dark cells. Peridium pseudoparenchymatous comprising hyaline to pale-brown, cell of textura angularis. Asci 8-spored, unitunicate, pear-shaped evanescent. Ascospores bi- to multi-seriate, allantoidal in side view, elliptical in face view and circular in end view surrounded by a thick, hyaline sheath, in end view apparent triangular, aseptate. Asexual morph: Hyphomycetous. Conidiophores synnematous or mononematous, erect, dark brown to black at the base, becoming light brown o subhyaline towards the apex. Conidiogenous cells annellidic, cylindrical, hyaline. Conidia unicellular, oblong or clavate to obovate, hyaline (adapted from Maharachchikumbura et al. 2016).
Type species: Ophiostoma piliferum (Fr.) Syd. & P. Syd., Annls mycol. 17(1): 43 (1919)
Notes: de Beer et al. (2013) accepted 134 species in Ophiostoma and some species areimportant tree pathogens, such as O. ulmi and O. novo-ulmi, the causal agents of Dutch elmdisease, transmitted by elm bark beetles (Webber & Gibbs 1989, Brasier 1991). The sexual morphis characterized by globose to subglobose ascomata, surrounded by external hairs, with ostiolarnecks and some species containing divergent, ostiolar hyphae. The asexual morph has sporothrix-like or pesotum-like conidiogenous cells with ellipsoidal to cylindrical obovate, globose andaseptate conidia.
Species illustrated in this entry:
Ophiostoma piliferum (Fr.) Syd. & P. Syd.