Submitted to: American Phytopathological Society Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 5/4/2009
Publication Date: 8/1/2009
Citation: Moore, G.G., Horn, B.W., Elliott, J.L., Hell, K., Chulze, S.N., Barros, G., Wright, G., Naik, M.K., Carbone, I. 2009. Sexual reproduction influences aflatoxin chemotype diversity in worldwide populations of Aspergillus flavus and A. parasiticus. American Phytopathological Society Abstracts. Interpretive Summary: None required.
Technical Abstract: Aflatoxins are toxic polyketides produced by several Aspergillus species that contaminate food crops worldwide. Aspergillus flavus and A. parasiticus are the most common agents of aflatoxin contamination of oil-rich crops. The genes involved in aflatoxin biosynthesis are clustered and convert acetate and malonate to aflatoxins B1, B2, G1, and G2. We determined the frequency of the MAT1-1 and MAT1-2 mating-type genes in A. parasiticus and A. flavus sampled from single peanut fields in the United States (Georgia), Africa (Benin), Argentina, Australia, and India. To determine whether sexual reproduction influences aflatoxin chemotype diversity, we tested the null hypothesis of an equal number of MAT1-1 and MAT1-2 in populations sampled from each locality/species using a two-sided binomial test. For both A. flavus and A. parasiticus, when the number of MAT1-1 and MAT1-2 was significantly different in both uncorrected and clone-corrected samples, isolates grouped into specific chemotypes, either the nonaflatoxigenic class in A. flavus or the B1-dominant and G1-dominant classes in A. parasiticus. In A. flavus, sexual reproduction suggested by a 1:1 distribution of MAT genes reduces the frequency of nonaflatoxigenic strains and increases the resolution of recombination blocks. In A. parasiticus, sexual reproduction and recombination reduces the frequency of B1-dominant and G1-dominant chemotypes, and isolate G1/B1 ratios show a continuous distribution in the population.