Mechanisms of Atoxigenicity: Characterizing Genetic Properties of Atoxigenic Aspergillus flavus Isolates

Abstract

Aspergillus flavus is the primary causal agent of aflatoxin contamination in crops. Aflatoxins are highly toxic carcinogens that threaten many agricultural systems throughout the world. Twentyeight genes located in a single aflatoxin biosynthesis gene cluster are required for aflatoxin production. A. flavus isolates that are not capable of producing aflatoxins (atoxigenics) have been utilized commercially as biocontrol agents. Atoxigenicity results from the modification of genes within the aflatoxin biosynthesis cluster. Mechanisms by which A. flavus isolates become atoxigenic are unknown for many atoxigenics. Twelve atoxigenic isolates under development as biocontrol agents in the United States and Africa were subjected to several genetic analyses including multiplex PCR and sequencing of aflatoxin biosynthesis genes. Deletion patterns within the aflatoxin gene cluster varied among the atoxigenics, but certain deletion patterns were shared by multiple isolates. Sequence analysis revealed that either breakpoints or insertions exist in several isolates. The data obtained from this study will be used to develop assays to interrogate large populations of A. flavus for specific DNA features. This will aid the search for elite atoxigenic vegetative compatibility groups with superior value as biocontrol agents and allow for monitoring specific genotypes in the environment for detection of adaptive differences.