Pleosporales » Didymosphaeriaceae

Didymosphaeria

Didymosphaeria Fuckel, Jb. nassau. Ver. Naturk. 23–24: 140 (1870).

Index Fungorum number: IF 1562; Facesoffungi number: FoF 00036, 195 morphological species (Species Fungorum 2022), 4 species with molecular data.

Terrestrial, saprobic or parasitic on woody branches and herbaceous stems and leaves, also parasitic on other fungi. Sexual morph: Ascomata solitary, scattered, or in small groups, immersed to erumpent, globose to ovoid, ostiolate. Ostiole papillate with a pore-like opening, ostiolar canal filled with hyaline cells (periphyses). Peridium 1-layered, thin, composed of brown pseudoparenchymatous cells of textura angularis. Hamathecium of dense, trabeculate, pseudoparaphyses, anastomosing mostly above the asci. Asci 2–4-spored, or 8-spored, bitunicate, fissitunicate, cylindrical, with a furcated pedicel, apically rounded with an indistinct ocular chamber. Ascospores uni-seriate, ellipsoid, brown, uniseptate, wall smooth or roughed. Asexual morph: see notes below (adapted from Hyde et al. 2013).

Type species: Didymosphaeria epidermidis (Fr.) Fuckel

Notes: Didymosphaeria is characterised by pycnidial or avervular, separate or aggregated conidiomata, enteroblastic, phialidic conidiogenous cells, and holoblastic, aseptate, falcate, fusiform, ellipsoidal to obovoid conidia. Saccardo (1882) accommodated taxa with only brown ascospores in Didymosphaeria and consequently more than 100 taxa were excluded by several authors (Barr 1989a, b, Hawksworth 1985, Hawksworth & Boise 1985, Hawksworth & Diederich 1988, Scheinpflug 1958, Aptroot 1995). At first, several authors considered Didymosphaeria epidermidis (Fries) Fuckel as the type species for Didymosphaeria but the latter comprised a coelomycete (Aptroot 1995). The type specimen of the original species D. rubi Fuckel was lost (Aptroot 1995). Hawksworth and David (1989) suggested to conserve Didymosphaeria with a lectotype specimen, D. futilis in Fungi Rhenani 1770 and this was followed by Hyde et al. (2013). Aptroot (1995), on the other hand chose Didymosphaeria epidermidis (Fr.) Fuckel as the lectotype specimen and this was followed by Hongsanan et al. (2020a). Aptroot (1995) mentioned seven species in Didymosphaeria without considering differences in host association or geographical distribution, excluded several genera from Didymosphaeriaceae and accepted Didymosphaeria based on the peridium comprising flattened or irregular cells, a hamathecium comprising narrow, trabeculate pseudoparaphyses and brown, thinly distoseptate ascospores. Sivanesan (1984) mentioned that Didymosphaeria has Ascochyta and Periconia asexual morph, while Kirk et al. (2008) linked Fusicladiella-like and Phoma-like taxa to Didymosphaeria. Zhang et al. (2012) described the type of D. futilis (Sphaeria futilis) and maintained Didymosphaeria as a distinct genus in Didymosphaeriaceae based on phylogenetic analyses. Ariyawansa et al. (2014) suggested that linking Didymosphaeria to asexual states must be done cautiously until a lectotype of D. futilis has been sequenced. Didymosphaeria is a well-defined genus in Didymosphaeriaceae but only four species have molecular data. More taxa with sequence data will help to better understand the taxonomy of Didymosphaeria. Molecular markers available for Didymosphaeria are LSU, SSU, Actin, RPB2 and TEF-1.

 

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