Submitted to: American Phytopathological Society Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 6/6/2007
Publication Date: 7/10/2007
Citation: Moore, G.G., Ramirez-Prado, J.H., Horn, B.W., Carbone, I. 2007. Evidence of extensive recombination in the aflatoxin gene cluster of Aspergillus flavus . American Phytopathological Society Annual Meeting. Interpretive Summary: None required.
Technical Abstract: Aflatoxins are toxic compounds produced by several Aspergillus species that contaminate crops worldwide. A. flavus is the most common agent of aflatoxin contamination of corn, peanuts, cottonseed, figs and tree nuts in the US. Extensive studies have elucidated the biochemical and regulatory mechanisms of aflatoxin production, but basic knowledge of the evolutionary processes that maintain toxicity in A. flavus is lacking. We sequenced 21 intergenic regions in the aflatoxin gene cluster for a sample of 43 isolates of A. flavus representing the genetic diversity within a single peanut field in Georgia. Linkage disequilibrium analyses revealed eight distinct recombination blocks that separate eight contiguous genes in the cluster (aflE, aflM, aflN, aflG, aflL, aflI, aflO, and aflP); blocks flanking each gene show a different evolutionary history. This block-like organization is the result of recombination among haplotypes representing distinct vegetative compatibility groups (VCGs). Nonaflatoxigenic A. flavus strains with complete clusters show divergent origins, and at least one distinct lineage is under the influence of balancing selection that is acting to stabilize the nonaflatoxigenic phenotype. Collectively, these evolutionary processes have significant implications for biocontrol strategies, which introduce nonaflatoxigenic strains into native populations.