Chaetodiplodia P. Karst., Hedwigia 23(4): 62 (1884).
Index Fungorum number: IF 9919; Facesoffungi number: FoF 01455, 3 morphological species (Species Fungorum 2022), molecular data available for unknown Chaetodiplodia sp.
Saprobic or endophytic on host. Sexual morph: Unknown. Asexual morph: Conidiomata pycnidial, superficial, dark brown to black, globose, solitary or occasionally gregarious, unilocular, ostiolate. Ostiole single, circular, central. Conidiomata wall composed of thin-walled, brown cells of textura angularis. Setae numerous, covering whole pycnidium, straight or flexuous, smooth, pale brown, usually aseptate, becoming septate at maturity, with obtuse apices, not markedly tapered. Conidiophores reduced to conidiogenous cells. Conidiogenous cells enteroblastic, phialidic, discrete, determinate, hyaline, smooth, ampulliform to doliiform, with narrow channel, minute collarette, periclinal wall thickening. Conidia cylindrical to ellipsoid, obtuse at apex, occasionally truncate at base, uniseptate, with prominent septum, continuous or occasionally slightly constricted, pale brown, eguttulate or guttulate, thin and smooth-walled (adapted from Sutton 1980; Tiwari and Rai 2009; Wijayawardene et al. 2016).
Type species: Chaetodiplodia caulina P. Karst.
Notes: Chaetodiplodia is characterised by pycnidial, superficial, dark brown to black conidiomata, several setae covering the whole pycnidium, enteroblastic, phialidic, discrete conidiogenous cells and cylindrical to ellipsoid conidia. van der Aa and van Kesteren (1979) synonymized Chaetodiplodia caulina as Ascochyta caulina. van der Aa and van Kesteren (1979) described Ascochyta caulina as having ‘sub-hyaline to yellowish green, olivaceous or seldom brownish’ conidia which did not fit the generic concept of Ascochyta s. str., whereby members have hyaline conidia (Sutton 1980). In the phylogenetic analyses of De Gruyter et al. (2009, 2013), comprising two Chaetodiplodia (CBS 568.88, CBS 453.68) and two Ascochyta caulina strains (CBS 2479, CBS 343.78), the Chaetodiplodia sp. (CBS 568.88) grouped in Leptosphaeriaceae, while two Ascochyta caulina strains together with Chaetodiplodia sp. (CBS 453.68) clustered in Pleosporaceae. De Gruyter et al. (2009) mentioned that Ascochyta caulina is the asexual morph of Pleospora calvescens while De Gruyter et al. (2013) considered Ascochyta caulina as a synonym of the latter species. Wijayawardene et al. (2016) maintained Chaetodiplodia caulina as a synonym of Pleospora calvescens based on morphological and phylogenetic analyses. De Gruyter et al. (2013) reported that Phoma betae clustered with other pycnidial taxa pathogenic on Chenopodiaceae, comprising Ascochyta obiones, A. hyalospora, A. caulina and Chaetodiplodia sp. All these taxa are similar in having hairy pycnidia, but are categorized in Ascochyta or Coniothyrium based on the conidial septation or brown conidial pigmentation. Wijayawardene et al. (2014) mentioned that in a personal communication, P.W. Crous pointed out that the strain CBS 453.68 differs from Chaetodiplodia and warrants a new genus rank hence identification of this group of taxa based on names in GenBank is not feasible. Chaetodiplodia is currently in Pleosporales genera incertae sedis and fresh collections with DNA sequence data are needed to confirm the taxonomic placement of the genus. Molecular markers available for Chaetodiplodia are LSU, SSU, RPB2 and Actin.