Pseudodidymella
Pseudodidymella C.Z. Wei, Y. Harada & Katum., Mycologia 89(3): 494 (1997).
Index Fungorum number: IF 27703; Facesoffungi number: FoF 08301, 2 morphological species (Species Fungorum 2022), 2 species with molecular data.
Pathogenic on leaves. Sexual morph: Pseudothecium epiphyllous, subcuticular with the base immersed, subglobose, dark brown to black, solitary or rarely confluent; the part of the ascoma that remains immersed stromatic, composed of dark-brown, thick-walled pseudoparenchymatoous cells up to 15 µm diam and arranged in many layers; asci and pseudoparaphyses forming in a locule in the upper portion. The peridium of the upper portion comprised of small brownish, flattened cells. The ostiolar opening preformed circular, periphysoids not seen. Pseudoparaphyses abundant among mature asci, threadlike, simple, hyaline, persisting. Asci forming in a hymenium, bitunicate, calvate to cylindrical, with round apex, short stalked, 8-spored. Ascospores 2-seriatein the ascus, fusoid,uniseptate, septum median or submedian, rarely becoming 2−3-septate at maturity, constricted at the septum, tapering towards both ends, rounded at the apex. Asexual morph: Leaf spots amphigenous, suborbicular to oblong, brownish, 1–4 cm diam. Conidiomata sporodochial, usually epiphyllous, whitish. Mycelium internal, hyphae hyaline, septate, branched. Stromata well-developed, subcuticular to intraepidermal, erumpent, composed of pseudoparenchymatous cells. Conidiophores arising from stromata, macronematous, cylindrical, simple, erect, or somewhat flexuous, very numerous in a dense fascicle, uniseptate, hyaline, smooth. Conidiogenous cells integrated, terminal, short cylindrical, determinate. Conidial scars more or less truncate, unthickened, colorless. Conidial ontogeny holoblastic. Conidia produced singly on conidiophores, narrowly obclavate, frequently curved, tapering towards the apex and often rostrate, more or less pointed, more or less attenuated towards the base, subtruncate or obconically truncate at the base, multi-septate, constricted at the septa, hyaline, smooth. Conidia laterally aggregated, becoming swollen in the middle and forming a white cup-like conidial mass after splitting from the conidiogenous cells. Each conidium at maturity disarticulating at septa into several individual cells in the middle and narrow cylindric fragments at the apex and base; individual cells from the middle ovoid to ellipsoid, fragments at the apex cylindric, narrow, 2-septate, fragments at the base cylindric, narrow, 0-1 septate. Chains of swollen, globose, dark-brown chlamydospores with granular, vacuolated cytoplasm may occur in hyphae of old cultures at low temperature (Adapted from Wei et al. 1997).
Type species: Pseudodidymella fagi C.Z. Wei, Y. Harada & Katum.
Notes: Pseudodidymella is characterised by epiphyllous, subcuticular, subglobose, dark brown to black, solitary pseudothecium, bitunicate, clavate to cylindrical asci and fusoid,uniseptate ascospores (Wei et al. 1997). Pseudodidymella resembles Mycodidymella, but is different based on the sporodochial conidiomata and appendage-bearing conidia (Wei et al. 1997). Hashimoto et al. (2017) included Pseudodidymella in Pseudodidymellaceae based on the mycopappus-like propagules and phylogenetic analysis. Hongsanan et al. (2020a) retained Pseudodidymella as a distinct genus in Melanommataceae. Molecular markers available for Pseudodidymella are ITS, LSU, SSU, TEF-1 and RPB2. More collections with DNA sequence data are needed to verify whether Pseudodidymella warrants separate familial rank.
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