Sphaeriothyrium Bubák, Ber. dt. bot. Ges. 34: 299 (1916)
Facesoffungi number: FoF 07593
Ascomycota, genera incertae sedis
Habit on petiole of Struthiopteris germanica (Onocleaceae), Pteridium aquilinum (Dennstaedtiaceae). Sexual morph: undetermined. Asexual morph: Conidiomata dark brown, stromatic, pycnidial, solitary, immersed to semi-immersed, subglobose, unilocular, glabrous. Ostiole absent, dehiscence by breakdown of the upper wall. Conidiomatal wall composed of thick-walled, dark brown cells of textura angularis in the exterior, becoming paler towards hymenium. Conidiophores arising all around the cavity of conidioma, reduced to conidiogenous cells. Conidiogenous cells hyaline, enteroblastic, phialidic, ampuliform to doliiform, determinate, smooth-walled, with a minute apical channel and collarette, periclinal thickening at the collarette zone. Conidia hyaline, ellipsoid to cylindrical, unicellular, smooth-walled, eguttulate (adapted from Sutton 1980).
Type species: Sphaeriothyrium filicinum Bubák, Ber. dt. bot. Ges. 34: 299
Notes: Sphaeriothyrium is similar to asexual morph of Plenodomus (e.g. P. lingam, syn. Phoma lingam) and Phoma in having pycnidial conidiomata producing ellipsoid to cylindrical or subcylindrical conidia (Verkley et al. 2014; Ariyawansa et al. 2015). However, no molecular data is available for this genus and it is, therefore, difficult to separate them by morphology. Fresh collections are needed to place it in a natural group and link it to its sexual morph.
Distribution: Germany, Italy (Sutton 1980; Index Fungorum 2020).
Sphaeriothyrium filicinum (redrawn from Sutton 1980) a Conidia. b Conidiogenous cells and developing conidium. c Vertical section of conidioma.