Didymochaeta Sacc. & Ellis, Bull. Torrey bot. Club 25: 510 (1898)
Facesoffungi number: FoF 07280
Ascomycota, genera incertae sedis
Saprobic on the host plant. Sexual morph: undetermined. Asexual morph: Conidiomata dark brown, pycnidial, solitary to gregarious, semi-immersed to superficial, globose, unilocular, glabrous. Ostiole single, circular, papillate, centrally located. Conidiomatal wall composed of thick-walled, dark brown cells of textura globulosa, often pruinose in the periphery, becoming thinner-walled, paler and then hyaline, small cells of textura angularis towards hymenium. Conidiophores formed from the inner wall of conidiomata, reduced to conidiogenous cells. Conidiogenous cells hyaline, enteroblastic, phialidic, doliiform, determinate, smooth-walled, with minute collarette but prominent channel and thickened periclinal walls. Conidia hyaline, cylindrical, obtuse at both ends, straight, 1–2-septate, constricted at the septa, smooth-walled, guttulate (Sutton 1980).
Type species: Didymochaeta americana Ellis & Sacc., Bull. Torrey bot. Club 25: 510 (1898)
Notes: Sutton (1980) gave a full account of Didymochaeta, and accepted four species in the genus, of which D. fraserae (Ellis & Everh.) B. Sutton, was assigned as the generic type, and D. americana was listed as a synonym of the type species. According to the priority principle (Hawksworth et al. 2012), D. americana is presently selected as generic type. Didymochaeta shares similar form of conidiomata, conidiogenous cells and conidia with Ascochyta. The only difference between these two genera is the conidiomatal wall structure. Didymochaeta has conidiomatal wall of textura globulosa to textura angularis, and often pruinose in the periphery, whereas Ascochyta has conidiomatal wall of textura angularis. Ascochyta and Didymochaeta might be taxonomically congeneric. However, Ascochyta is a polyphyletic genus as Phoma (Aveskamp et al. 2010); no molecular data is available for Didymochaeta. Therefore, fresh collections of D. americana are needed to place Didymochaeta in a natural group.
Distribution: Argentina, USA.
Didymochaeta americana (redrawn from Sutton 1980) a Vertical section of conidioma. b Conidia. c Conidiogenous cells and developing conidia.
Li WJ, McKenZie EHC, Liu JK, Bhat DJ, Dai DQ, Caporesi E, Tian Q, Maharachcikumbura SSN, Luo ZL, Shang QJ, Zhang JF, Tangthirasunun N, Karunarathna SC, Xu JC, Hyde KD (2020) Taxonomy and phylogeny of hyaline-spored coelomycetes. Fungal Diversity 100: pages279–801.