Protofenestella Jaklitsch & Voglmayr, in Jaklitsch et al., Stud. Mycol. 90: 109 (2017).
Index Fungorum number: IF 823018; Facesoffungi number: FoF 08187, 1 morphological species (Species Fungorum 2022), 1 species with molecular data.
Saprobic in bark. Sexual morph: Ascomata globose, pyriform, depressed subglobose to lenticular, immersed below the host epidermis, solitary or randomly disposed, loosely or densely aggregated in often large ill-defined groups, not forming defined pustules, inconspicuous at the bark surface, surrounded by subiculum. Ostioles inconspicuous, short and blunt conical. Peridium pseudoparenchymatous, covered with subicular hyphae outside, becoming lighter and thinner walled toward inner side. Hamathecium formed by numerous richly branched paraphyses. Asci cylindrical, bitunicate, fissitunicate, with an ocular chamber, short stipe and a simple or knob-like base, comprising (4–)8 (obliquely or partly overlapping) uniseriately arranged ascospores. Ascospores ellipsoid to fusoid, symmetric to slightly asymmetric, first hyaline to yellowish, with 3–4(–5) transverse septa, developing a longitudinal septum; wall distinctly thicker than septa except for the ends containing narrow canals; later brown to dark brown, with several transverse and longitudinal septa; not to distinctly constricted at the median to slightly eccentric primary septum; ends often lighter colored, brownish to hyaline, often protruding and subacute, pierced by a pore and often with a hyaline roundish to cylindrical cellular appendage at one or both ends; turning blackish brown in 3 % KOH. Asexual morph in culture: Pycnidia more or less globose, papillate, nearly black. Peridium thin pseudoparenchymatous. Phialides sessile, clustered in small groups or short chains, subglobose to lageniform. Conidia 1-celled, oblong to allantoid or ellipsoid, hyaline, guttulate, smooth (adapted from Jaklitsch et al. 2018).
Type species: Protofenestella ulmi Jaklitsch & Voglmayr
Notes: Protofenestella is characterised by globose, pyriform, depressed subglobose to lenticular ascomata, inconspicuous, short and blunt conical ostioles, cylindrical, bitunicate, fissitunicate asci and ellipsoid to fusoid, symmetric to slightly asymmetric ascospores. Protofenestella differs from Fenestella in having solitary or randomly disposed ascomata while the latter has clustered ascomata. Protofenestella also resembles Pleomassaria but is distinct in having ascospores with fewer longitudinal septa and the presence of a swelling sheath. Protofenestella can also be differentiated from Fenestella and Pleomassaria based on DNA sequence data. Protofenestella is morphologically and phylogenetically a well-defined genus in Cucurbitariaceae. Molecular markers available for Protofenestella are ITS, LSU, BTUB, RPB2 and TEF-1.