Chaetosphaeronema Moesz, Bot. Közl. 14: 152 (1915).
Saprobic or pathogenic on host. Sexual morph: Unknown. Asexual morph: Unknown. Conidiomata pycnidial, scattered, immersed to semi-immersed, uniloculate, globose, setose, brown to dark brown, ostiole central, with setose papilla. Conidiomata walls thin, arranged in a textura prismatica, pale brown, outer layers comprising dark brown, thick-walled cells. Conidiophores arising from basal cavity of conidiomata mostly reduced to conidiogenous cells. Conidiogenous cells enteroblastic, phialidic, discrete or integrated, cylindrical, hyaline, smooth-walled, with minute channel or collarette, hardly distinguishable from the inner wall cells. Conidia didymosporous, oblong to cylindrical, with obtuse ends, straight or slightly curved, hyaline, 1-septate, thin and smooth-walled, with guttules (adapted from Sutton, 1980 and Quaedvlieg et al., 2013).
Type species: Chaetosphaeronema hispidulum (Corda) Moesz
Notes: Chaetosphaeronema was introduced by Moesz (1915) with C. hispidulum as type species. Chaetosphaeronema is characterized by pycnidial conidiomata, enteroblastic, phialidic, discrete or integrated, cylindrical, hyaline conidiogenous cells and didymosporous, oblong to cylindrical conidia. Chaetosphaeronema hispidulum was previously known as Sphaeronaema hispidulum but was not congeneric with the type species of Sphaeronaema, S. cylindricum. Sutton (1980) provided a morphological account of Chaetosphaeronema. Petrak (1944) considered Ch. herbarum as a synonym of Ch. hispidulum and accepted three species viz Ch. collivagum (Petr.) Petr., Ch. galii (Petr.) Petr. and Ch. hispidulum (Sutton 1980). Several authors considered Chaetosphaeronema limited only to the type species, C. hispidulum (De Gruyter et al., 2009, 2010; Zhang et al., 2012; Hyde et al., 2013; Quaedvlieg et al., 2013; Phookamsak et al., 2014). In the phylogenetic analysis of De Gruyter et al. (2009), the strain Chaetosphaeronema hispidulum (CBS 216.75) formed a distinct lineage sister to Phoma haematocycla (CBS 175.93) and hence was accommodated in Phaeosphaeriaceae. De Gruyter et al. (2010) added a new species Ch. coonsii and treated Chaetosphaeronema sensu stricto in Phaeosphaeriaceae. This taxonomic placement was followed by subsequent authors (Schoch et al., 2009; Zhang et al., 2009, 2012; Hyde et al., 2013; Quaedvlieg et al., 2013). In the phylogenetic analysis of Phookamsak et al. (2014), Chaetosphaeronema formed a distinct lineage close to Ophiobolus cirsii (MFLUCC13-0218). Petrak (1944) and Zhang et al. (2009) suggested that Chaetosphaeronema might be the asexual state of Ophiobolus but this was not proven with molecular data. Chaetosphaeronema is currently a distinct genus in Phaeosphaeriaceae but more taxa with molecular data is needed to confirm the sexual and asexual relationship of the genus. Molecular markers available for the genus are LSU, SSU, ITS, RPB2 and TEF1.