DNA relatedness among wild and domesticated species in the Aspergillus flavus group

The aflatoxin-producing fungi Aspergillus flavus and A. parasiticus show many phenotypic similarities with the nonaflatoxigenic species A. oryzae and A. sojae which are widely used in food fermentations. Absence of teleomorphic states has prevented clarification of relationships through conventional genetic means and molecular comparisons have not been previously reported. Our data show that all four species have high (69-100%) nuclear DNA complementarity and similar genome size. These findings indicate that the four taxa represent a single species. The data support the concept that A. oryzae and A. sojae were derived (domesticated) from the naturally occurring A. flavus and A. parasiticus through their adaptation to a koji environment.