Ascodichaena Butin, Trans. Br. Mycol. Soc. 69(2): 249 (1977) = Polymorphum Chevall., J. Phys. Chim. Hist. nat. Arts 94: 32 (1822)
Leotiomycetes, Leotiomycetidae, Medeolariales, Ascodichaenaceae
Saprobic on the host plant in terrestrial habitat. Sexual morph: see Butin (1977) and Hawksworth (1983). Asexual morph: Conidiomata dark brown to black, pycnidial, gregarious, initially immersed, ultimately become erumpent, hysteriform to irregularly disciform, unilocular, glabrous, ostiolate. Ostiole slit-like, opening by a simple, divided or stellate fissure. Conidiomatal wall composed of thick walled, brown to hyaline cells of textura prismatica at the basal part, becoming thick-walled, dark brown to hyaline cells of textura angularis at lateral upper part. Conidiophores arising from the innermost layers of conidiomata, hyaline, cylindrical, branched near the base, 1–5 septate, becoming swollen towards apex, smooth-walled. Conidiogenous cells hyaline, holoblastic, cylindrical, determinate, smooth-walled. Conidia hyaline, globose to ovoid, unicellular, smooth-walled, guttulate, becoming delimited from the conidiogenous cells either by the formation of a thin septum or breaking off with the conidiogenous cell still attached and appearing pedicellate (Hawksworth and Punithalingam 1973; Butin 1977).
Type species: Ascodichaena rugosa Butin, Trans. Br. Mycol. Soc. 69(2): 249 (1977) = Polymorphum fagineum (Pers.) Chevall., J. Phys. Chim. Hist. nat. Arts 94: 33 (1822) = Polymorphum quercinum (Pers.) Chevall., J. Phys. Chim. Hist. nat. Arts 94: 33 (1822) = Polymorphum rugosum (L.) D. Hawksw. & Punith., Trans. Br. Mycol. Soc. 60(3): 503 (1973)
Notes: Polymorphum is characterized by hysteriform to irregularly disciform conidiomata and globose to ovoid, aseptate conidia. Polymorphum was introduced to accommodate two species, P. fagineum and P. quercinum, but neither was selected as type species. Hawksworth and Punithalingam (1973) discussed the synonym of Polymorphum, and lectotypified P. rugosum as a generic type. Hawksworth (1983) revised the nomenclature of Polymorphum and Ascodichaena, and connected the former to the latter sexual morph. He also applied P. quercinum as a generic type of Polymorphum. However, Polymorphum quercinum is a synonym of P. rugosum (Johnston et al. 2014). Based on “one fungus, one name” principle, Johnston et al. (2014) synonymized Polymorphum under Ascodichaena. No molecular data is available for Ascodichaena.
Distribution: Canada, France, Germany, Mexico, Pakistan, UK (Sutton 1980).
Ascodichaena rugosa (asexual morph, redrawn from Morgan-Jones 1974) a Vertical section of conidioma. b Conidiophores, conidiogenous cells, developing conidia and 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.