Sexual reproduction in aflatoxin-producing Aspergillus nomius

Abstract

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.

• Aflatoxin
• ascospores
• Aspergillus flavus
• Aspergillus parasiticus
• heterothallism
• Petromyces

We appreciate the help of Patricia Eckel who prepared the Latin diagnosis, Travis Walk and Bryan Cody for technical assistance and Valerie Knowlton at the Center for Electron Microscopy (NC State University) for assistance with SEM. This work was supported in part by the National Research Initiative of the USDA Cooperative State Research, Education and Extension Service to IC (grant number 2005-35319-16126).