Ascochyta Lib., Plantae Cryptogamae, quas in Arduenna collegit Fasc. 1: 8 (1830).

    = Didymochaeta Sacc. & Ellis, Bull. Torrey bot. Club 25: 510 (1898)

MycoBank number: MB 7239; Index Fungorum number: IF 7239; Facesoffungi number: FoF 07121; 723 morphological species (Species Fungorum 2020), 18 species with molecular data.

Saprobic or parasitic on the host plant. Sexual morph: see Chilvers et al. (2009). Asexual morph: Conidiomata dark brown to black, pycnidial, solitary to gregarious or confluent, immersed to semi-immersed, globose or subglobose, unilocular, glabrous, papillate, ostiolate. Ostiole single, circular, papillate or non-papillate, centrally located. Conidiomatal wall composed of thick-walled, dark brown to paler cells of textura angularis. Conidiophores arising all around the cavity of the conidiomata, reduced to conidiogenous cells. Conidiogenous cells hyaline, enteroblastic, annellidic or phialidic, subcylindrical to lageniform or ampuliform to dolliform, determinate, smooth-walled. Conidia hyaline, oblong to cylindrical, straight or slightly curved, 0–2-septate, slightly constricted at the septa, smooth-walled, guttulate (Chen et al. 2015).

Type species – Ascochyta pisi Lib., Pl. crypt. Arduenna, fasc. 1: no. 59. 1830.

Notes – Ascochyta is a well-known pathogenic genus in Didymellaceae. Earlier this genus was described using its sexual morphs and Chen et al. (2015) linked asexual morph to this genus. They are characterised by oblong to ellipsoidal aseptate conidia in Didymellaceae. The host-specificity of the species belonging to this genus is rather restricted, and they occur mostly in the Campanulaceae, Chenopodiaceae, Leguminosae, Poaceae, Solanaceae and Umbelliferae (Valenzuela-Lopez et al. 2018). Some species are associated with one specific host but may also be found on other related species of the same genus or family (Boerema & Bollen 1975). Even though there are 1438 records in Index Fungorum (2020) and 1347 records available in Mycobank (2020), currently only 18 species are accepted including two varieties of Ascochyta medicaginicola (Chen et al. 2017, Jayasiri et al. 2017b, Valenzuela-Lopez et al. 2018, Hyde et al.2018, Wanasinghe et al. 2018b). This genus is often confused with Phoma, as both genera are similar in morphology, physiology, pathogenicity and nucleotide sequences (Boerema and Bollen 1975; Mendes-Pereira et al. 1999; Davidson et al. 2009; De Gruyter et al. 2009, 2010; Aveskamp et al. 2010). Chen et al. (2015) clarified the generic circumscriptions of Ascochyta and Phoma, and emended the generic concept for both genera based on multigene sequence data of ITS, LSU, rpb2 and tub2 and morphology characters. Since then, three additional species have been described, A. boeremae L.W. Hou et al., A. italica Tibpromma et al. and A. rosae Tibpromma et al. (Chen et al. 2017; Tibpromma et al. 2017). However, A. rosae Tibpromma et al. with both sexual and asexual morph is identical to A. herbicola in morphology and phylogeny, and is synonymized under the latter.

Distribution – worldwide.

Species