Coniozyma Crous, in Marincowitz, Crous, Groenewald & Wingfield, CBS Diversity Ser. (Utrecht) 7: 97 (2008).
Leaf spots amphigenous, irregular, grey to light brown with a raised, dark brown border, frequently associated with tip blight or leaf margins. Sexual morph: Unknown. Asexual morph: Conidiomata pycnidial, subepidermal, substomatal, amphigenous, separate, visible as dark brown spots; in section, globose, apapillate, sometimes surrounded by a stroma comprising host cells and dark brown fungal hyphae; in section in vitro, globose occasionally becoming cupulate at maturity. Peridium consisting of two strata of cells in a slightly compressed textura angularis to globulosa, outer stratum of thick-walled brown cells sometimes having almost occluded lumens, becoming thinner walled and hyaline inwardly; in vitro consisting of two strata of cells of textura globulosa, outer stratum of thick-walled brown cells, becoming thinner walled and hyaline inwardly. Conidiophores reduced to conidiogenous cells, often invested in mucus. Conidiogenous cells discrete, smooth or slightly verruculose, hyaline to light brown, doliiform to ampulliform, proliferating 1–3 times enteroblastically and percurrently. Conidia vary in size, coloration and walled ornamentation, but broadly similar in shape, varying from hyaline to dark red-brown, thick-walled, faintly verruculose to echinulate, aseptate, ellipsoidal to globose, apex obtuse, base bluntly rounded to truncate, initially hyaline and thick-walled, becoming medium-brown, smooth to verruculose, ellipsoidal to globose and often irregularly shaped, apex obtuse, base bluntly rounded to truncate. Conidia show more variation in shape in vitro, but remain more consistent in size (adapted from Swart et al. 1998).
Type species: Coniozyma leucospermi (Crous & Denman) Crous
Notes: Coniozyma is characterised by pycnidial, subepidermal, substomatal conidiomata, doliiform to ampulliform conidiogenous cells, hyaline to dark red-brown conidia. The identification of Coniozyma has been reported as problematic due to inconsistent coloration, ornamentation and variable size of the conidia. Cultures of Coniozyma are olivaceous-black with slimy growth and can be wrongly identified as yeast contaminants. Coniozyma is also unique in producing budding of cells from germ tubes showing direct conidiogenesis from hyphae. Conidia of Coniozyma in culture are more variable in shape and size compared to the conidia on the natural substrate (Swart et al. 1998). Swart et al. (1998) reported that cultures should be kept in dark for a period of 2 to 4 weeks as a standard condition for the growth of the fungus. The taxonomic placement of Coniozyma is doubtful and is currently in Dothideales, genera incertae sedis. Fresh collections and DNA sequence data are needed to confirm the taxonomic placement of the genus.