Sexual reproduction in aflatoxin-producing Aspergillus nomius.

Sexual reproduction was examined in the aflatoxin-producing fungus Aspergillus nomius. Crosses between sexually compatible strains resulted in the formation of multiple nonostiolate ascocarps within stromata, which places the teleomorph in genus Petromyces. Ascocarp and ascospore morphology in Petromyces nomius were similar to that in P. flavus and P. parasiticus, and differences between teleomorphs were insufficient for species separation. Formation of mature ascocarps was infrequent, with only 24% of the 83 crosses producing viable ascospores. The majority of P. nomius strains contained a single mating-type gene (MAT1-1 or MAT1-2), but several strains contained both genes. MAT1-1/MAT1-2 strains were self-sterile and capable of mating with both MAT1-1 and MAT1-2 strains; hence P. nomius appears to be functionally heterothallic.