Comparison of Aspergillus flavus and Aspergillus oryzae by amplified fragment length polymorphism

The aflatoxin producer Aspergillus flavus and the koji mold Aspergillus oryzae are morphologically similar species that belong to the Aspergillus section Flavi. We used amplified fragment length polymorphism (AFLP) to differentiate these two species. In this study, we tested thirteen A. flavus, nine A. oryzae, and three A. flavus var. columnaris strains. DNA fragment profiles amplified with each of three selective primer pairs displayed similar patterns for the various A. flavus strains. Different patterns were observed with these primer pairs for the A. oryzae strains. We combined these data to increase the grouping of the various strains within each species and to distinguish between A. flavus and A. oryzae. By unweighted pair group method with arithmetic average (UPGMA) analysis, the AFLP data obtained from the three selective primer pairs, EcoRI-AC/MseI-CAT, EcoRI-TA/MseI-CAT, and EcoRITA/MseI-CTT, differentiated A. flavus from A. oryzae successfully. Three strains of A. flavus received from ATCC grouped outside of the other A. flavus strains we examined. The morphology of these isolates and our results indicated those strains were originally misidentified and they should be classified as A. parasiticus. We found that the AFLP technique is a reliable and reproducible tool with the ability to differentiate A. flavus from A. oryzae and should be generally useful in distinguishing between closely related species or strains.