Acrocalymma

Acrocalymma Alcorn & J.A.G. Irwin, Trans. Br. mycol. Soc. 88(2): 163 (1987)

= Rhizopycnis D.F. Farr, Mycologia 90(2): 291 (1998)

Citation when using this entry, Chen C. et al. in prep. – An updated monograph of Coelomycetes, Mycosphere

Index Fungorum, Facesoffungi number, MycoBank, GenBank           

Classification: Acrocalymmaceae, Pleosporales, Dothideomycetes, Ascomycota, Fungi

Pathogenic or saprobic on hosts in both terrestrial and freshwater habitats. The sexual morph is characterised by ascomata which are immersed to erumpent, covered with light pale grey hyphae, globose, unilocular, ostiolate with a long break. The ostiole is cylindrical, filled with hyaline periphyses and located in the centre. The peridium is constituted by brown, thick-walled cells forming a textura angularis. The hamathecium is comprised of hyaline, septate, flliform, anastomosed pseudoparaphyses and asci. Asci are 8-spored, bitunicate, cylindrical and short pedicellate. Ascospores are biseriate, narrowly fusiform, straight or slightly curved, hyaline when immature, brown or pale reddish brown at maturity, guttulate, 1–3-septate, constricted at septa, thick-walled, surrounded by 1–2 µm wide hyaline sheath (Shoemaker et al. 1991, Li et al. 2020). The asexual morph is characterised by the dark brown immersed to semi-immersed pycnidial conidiomata, which are dark brown to black, globose to subglobose, pyriform, separate or aggregated, unilocular or multi-locular, and ostiolate. The ostiole is cylindrical, circular, straight or curved, and located in the centre or on the side. The pycnidial wall is comprised of textura angularis to textura globosa or textura prismatica, thick-walled and brown to paler cells. Conidiophores are reduced to conidiogenous cells. Conidiogenous cells are enteroblastic, phialidic, ampulliform to subcylindrical or lageniform, hyaline and smooth-walled. Conidia are hyaline, aseptate or 1–3-septate, cylindrical to fusiform, with helmet-shaped mucoid appendage at each end (Alcorn & Irwin 1987, Li et al. 2020).

Type species: Acrocalymma medicaginis Alcorn & J.A.G. Irwin, Trans. Br. mycol. Soc. 88(2): 163 (1987)

Note: Acrocalymma was introduced by Alcorn and Irwin (1987) based on A. medicaginis as the type species, which was associated with a root and crown rot disease of Medicago sativa. Trakunyingcharoen et al. (2014) considered Rhizopycnis as a synonym of Acrocalymma based on both morphology and phylogeny and introduced A. vagum as a new combination for Rhizopycnis vagum (type species of Rhizopycnis). Trakunyingcharoen et al. (2014) also introduced a new family Acrocalymmaceae in Dothideomycetes to accommodate Acrocalymma. There are five species (A. arengae, A. chuxiongense, A. hongheense, A. pterocarpi, and A. walkeri) in Acrocalymma are described with sexual morphs and the rest are reported as asexual coelomycetous species (Calabon et al. 2023). Li et al. (2020) re-examined the type material of A. medicaginis and provided its description and illustrations. Species Fungorum (September 2024) lists 18 species in Acrocalymma. All species of Acrocalymma have sequences in GenBank (September 2024). The updated taxonomic treatment of this genus is Acrocalymmaceae, in Pleosporales (Dothideomycetes) (Wijayawardene et al. 2022).

For all accepted species: see Species Fungorum, search Acrocalymma.