Submitted to: Mycological Society of America
Publication Type: Abstract only
Publication Acceptance Date: 9/13/2008
Publication Date: 9/13/2008
Citation: Moore, G., Horn, B.W., Elliott, J., Hell, K., Chulze, S., Wright, G., Naik, M., Carbone, I. 2008. Recombination, balancing selection and geographic subdivision among worldwide populations of Aspergillus flavus. Mycological Society of America. Interpretive Summary: NONE REQUIRED
Technical Abstract: Aspergillus flavus is a global agent of aflatoxin contamination of economically important crops such as corn, peanuts, and cottonseed. 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 of 166 isolates of A. flavus representing geographically isolated populations from five countries (Argentina, Australia, Benin, India and United States). Linkage disequilibrium analyses of molecular variation revealed a different block-like organization for each population suggesting that populations are reproductively isolated. Detailed compatibility analyses for a single population from Georgia showed that all blocks, with the exception of aflM/aflN (hypE), shared the same evolutionary history. Further analyses on the entire sample revealed a signature of balancing selection within hypE and aflW/aflX, which acts to stabilize the nonaflatoxigenic phenotype. Although we detected significant geographic differentiation in noncluster regions, balancing selection in hypE and aflW/aflX decreased genetic differentiation among Australia, India and Georgia. These results may offer insight into the stability of potential biocontrol strains as well as those currently in use.