Xenomycosphaerella Quaedvl. & Crous, in Quaedvlieg et al., Persoonia 33: 24 (2014).
Index Fungorum number: IF 807787; Facesoffungi number: FoF 08569, 2 morphological species (Species Fungorum 2022), 2 species with molecular data.
Saprobic or pathogenic on leaf. Sexual morph: Leaf spots amphigenous, irregular to subcircular, medium brown, with a thin, raised, dark brown to red-brown border. Ascomata pseudothecial, amphigenous, but predominantly epiphyllous, dark brown, sub epidermal to somewhat erumpent, globose. Peridium comprising 2–3 layers of medium brown cells of textura angularis. Asci aparaphysate, fasciculate, bitunicate, sub sessile, obovoid to broadly ellipsoidal, straight to slightly curved, 8-spored. Ascospores tri- to multi-seriate, overlapping, hyaline, guttulate, thin-walled, straight to slightly curved, fusoid-ellipsoidal with obtuse ends, widest in middle of apical cell, uniseptate, constricted at the septum, tapering towards both ends, but more prominently towards the lower end, basal cell frequently longer than apical cell. Ascospores germinate from both ends, with germ tubes parallel to the long axis of the spore; spore not darkening, nor distorting. Asexual morph: Unknown (adapted from Quaedvlieg et al. 2014).
Type species: Xenomycosphaerella elongata (Crous & M.J. Wingf.) Quaedvl. & Crous
Notes: Xenomycosphaerella resembles Mycosphaerella but it is characterised by longer ascospores which differ from other species of Mycosphaerella. Xenomycosphaerella is a morphologically and phylogenetically distinct genus in Mycosphaerellaceae. Molecular markers available for Xenomycosphaerella include ITS, LSU, Actin, BTUB, Calmodulin, TEF-1 and RPB2.