Rhachisphaerella U. Braun, C. Nakash., Videira & Crous, in Videira et al., Stud. Mycol. 87: 337 (2017).
Index Fungorum number: IF 08559; Facesoffungi number: FoF 08559, 1 morphological species (Species fungorum 2021), 1 species with molecular data.
Phytopathogenic. Ascomata amphigenous, dark brown, subepidermal, becoming erumpent, globose; wall composed of layers of medium brown textura angularis. Asci aparaphysate, fasciculate, bitunicate, subsessile, obovoid to broadly ellipsoid, straight to slightly curved, 8-spored. Ascospores bi- to tri-seriate, overlapping, hyaline, thin-walled, straight to curved, fusoid-ellipsoidal with obtuse ends, widest in middle of apical cell, medianly 1- septate, not to slightly constricted at the septum, tapering towards both ends but more prominently towards the lower end; ascospores becoming distorted upon germination, becoming constricted at the septum, with irregular, wavy germ tubes, growing 90° to the long axis, and not arising from the polar ends of the spore. (In vitro) Mycelium submerged and superficial; submerged hyphae hyaline to sub hyaline, thin-walled, smooth or slightly rough; aerial hyphae pale olivaceous, smooth or finely verruculose. Conidiophores arising from hyphae, occasionally reduced to conidiogenous cells, hyaline, sub cylindrical. Conidiogenous cells integrated, terminal, proliferating sympodially, polyblastic, conidiogenous loci aggregated, flat, not protuberant (not denticle-like), unthickened, but somewhat darkened. Conidia solitary, hyaline, thin-walled, smooth, obovoid, ellipsoidal, obclavate, aseptate or multiseptate, hilum truncate, flat, broad, unthickened, slightly darkened (Adapted from Arzanlou et al. 2008).
Type species: Rhachisphaerella mozambica (Arzanlou & Crous) Videira & Crous
Notes: Rhachisphaerella was introduced by Braun et al. (2017) with R. mozambica as type species. Rhachisphaerella mozambica, previously known as Mycosphaerella mozambica was found on Musa species in Mozambique (Arzanlou et al. 2008). Rhachisphaerella resembles Ramichloridium in having sympodially proliferating conidiogenous cells. In the phylogenetic analyses of Videira et al. (2017), Rhachisphaerella forms a single species lineage close to Micronematomyces. Morphologically, R. mozambica differs from Micronematomyces in having conidiogenous cells that form a rachis with unthickened conidiogenous loci and obovoid, 0–1- septate conidia with unthickened hila.