Chaetomella Fuckel, Jb. nassau. Ver. Naturk. 23-24: 401 (1870) [1869-70]
Leotiomycetes, Leotiomycetidae, Chaetomellales, Chaetomellaceae
Saprobic or parasitic on the host plant in terrestrial habitat or isolated from soil. Sexual morph: undetermined. Asexual morph: Conidiomata two types: pycnidial or sporodochial. Pycnidia initially pale brown, ultimately dark brown to black, superficial, separate or gregarious, oblong, elongate or reniform, rarely globose to irregularly shaped, sessile or short stipitate, unilocular, setose. Pycnidial setae brown, unbranched, straight, curved, or coiled, septate, thick- and smooth-walled, with clavate to acuminate apex. Ostiole absent, dehiscing by an elongate, longitudinal slit in the upper part. Pycnidial wall composed of hyaline, 1-2 layers of thick-walled cellsin the outer region, merging with dark brown, 2–4 layers layers of thick-walled cells in the middle region, become hyaline, 3–4 layers layers of thick-walled cells of textura prismatica to textura angularis in the inner region. Conidiophores arising from all around the cavity of pycnidium, often more numerous toward base, hyaline, filiform, cylindrical, branched,. Conidiogenous cells hyaline, enteroblastic, phialidic, cylindrical, integrated, indeterminate, smooth-walled, forming acropleurogenously singly or in pairs below septa and at apices of conidiophores. Conidia hyaline, ellipsoid to fusiform or falcate, broadly rounded to slightly pointed at both ends, straight or slightly curved, unicellular, smooth-walled. Sporodochia pale brown to dark brown, discoid or crown-like at maturity, stalked, opening irregularly at apices with wavy margin, setose. Conidiophores, conidiogenous cells and conidia in sporodochial state similar to those in pycnidia (Rossman et al. 2004)
Type species: Chaetomella oblonga Fuckel, Jb. nassau. Ver. Naturk. 23-24: 402 (1870) [1869-70]
Notes: Chaetomella is characterized by pycnidial or sporodochial conidiomata with brown, unbranched setae, long, acropleurogenous conidiophores, and hyaline ellipsoid to fusiform or falcate, unicellular conidia (Sutton 1980, Rossman et al. 2004). Rossman et al. (2004) revised Chaetomella and listed the synonyms of the genus. They assigned Chaetomella to Leotiomycetes based on SSU and LSU sequence data and accepted four species and one variety e.g., C. acutiseta B. Sutton & A.K. Sarbhoy, C. circinoseta Stolk, C. raphigera Swift, C. oblonga Fuckel, and C. acutiseta var. nigra. Crous et al. (2014b, 2019) added C. zambiensis Crous on undetermined host (Fabaceae). and C. pseudocircinoseta Crous & Carnegie on on leaves of Eucalyptus microcorys (Myrtaceae). The sexual morph of this genus is undetermined.
Distribution: Australia, Canada, USA, India, Zambia (Rossman et al. 2004, Crous et al. 2014b, 2019)
Chaetomella oblonga (redrawn from Rossman et al. 2004) a Vertical section of pycnidium. b Vertical section of sporodochium c Conidiophores, conidiogenous cells. d Conidiomatal setae. e Conidia.
Li WJ, McKenZie EHC, Liu JK, Bhat DJ, Dai DQ, Caporesi E, Tian Q, Maharachcikumbura SSN, Luo ZL, Shang QJ, Zhang JF, Tangthirasunun N, Karunarathna SC, Xu JC, Hyde KD (2020) Taxonomy and phylogeny of hyaline-spored coelomycetes. Fungal Diversity 100: pages279–801.