Platychora
Platychora Petr., Annls mycol. 23(1/2): 102 (1925).
Index Fungorum number: IF 4169; Facesoffungi number: FoF 08231, 2 morphological species (Species Fungorum 2022), 1 species with molecular data.
Saprobic on dead leaves of Ulmus sp. Sexual morph: Stromata up to 1 mm broad, sub-epidermal, solitary to aggregated, superficial, cushion-shaped, multi-loculate, black. Locules immersed in stromatic tissues, globose to subglobose, coriaceous, papillate, ostiolate. Peridium comprising thick-walled, dark brown cells of textura angularis. Hamathecium comprising filiform, hyaline, branched pseudoparaphyses. Asci 8-spored, bitunicate, cylindrical, short pedicellate. Ascospores obliquely uniseriate, apiosporous, hyaline, ovoid, with a transverse septum near the lower end, not constricted at the septum. Asexual morph: Conidiomata subcuticular, acervular, brown to black, applanate to pulvinate. Conidiophores reduced to conidiogenous cells. Conidiogenous cells solitary, septate at the base, olivaceous, smooth, cylindrical, straight, holoblastic, annellidic. Conidia oval, pale brown, aseptate, thin-walled, smooth, ornamented (adapted from Hyde et al. 2016).
Type species: Platychora ulmi (J. Schröt.) Petr.
Notes: Platychora is characterised by cushion-shaped, multi-loculate, black stromata, bitunicate, cylindrical, short pedicellate asci, and apiosporous, hyaline, ovoid ascospores. The asexual morph is characterised by brown to black, applanate to pulvinate conidiomata, olivaceous, smooth, cylindrical conidiogenous cells, and oval, pale brown, aseptate, thin-walled conidia. Platychora is unique in producing multi-loculate stromatic tissues and apiospores. The taxonomic placement of Platychora was doubtful for many years. Winton et al. (2007) placed Platychora in Pleosporales, family incertae sedis. Hyde et al. (2013) accommodated Platychora in Didymellaceae based on a multigene analysis of ITS, LSU, RPB2 and BTUB gene. Hyde et al. (2016) illustrated the asexual morph of P. ulmi in culture and confirmed the placement of Platychora in Didymellaceae. Platychora is morphologically and phylogenetically a distinct genus in Didymellaceae. Molecular markers available for Platychora are ITS, LSU, SSU.
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