Submitted to: The Scientific World
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/5/2014
Publication Date: 11/12/2014
Citation: Solorzano Torres, C.D., Abbas, H.K., Zablotowicz, R.M., Chang, P., Jones, W.A. 2014. Genetic variability of Aspergillus flavus isolates from a Mississippi corn field. The Scientific World. 2014: 8 pages.
Interpretive Summary: Contamination of food crops with toxins produced by the fungus Aspergillus flavus (aflatoxins) is a major food safety concern. A biological approach to reduce the impact of toxin-producing (toxigenic) Aspergillus is using Aspergillus strains that do not produce toxins (non-toxigenic) to displace the toxin-producing fungi. To understand the ecology of toxin and non-toxigenic Aspergillus, the genes encoding for aflatoxin were sequences in a collection of isolates from a Mississippi field. We found two gene groups (haplotypes) that were predominant in the population, H1 (n=71, 60%) and H49 (n=18, 15%), with other groups being less common. H1 haplotype is a similar to a toxigenic strain and H49 is similar to K49 a non-toxigenic strain being developed for biocontrol. This study provides valuable information on the diversity of Aspergillus from a Mississippi corn field that can be further used to improve the efficacy of biological control strains and be used by researchers, and by biotechnology companies.
Technical Abstract: The fungus Aspergillus flavus represents a major threat to food safety and food security on a worldwide scale. Corn, peanuts, cotton, rice and edible nuts, can be colonized by A. flavus strains that produce carcinogenic aflatoxins. A biological strategy for control of toxigenic A. flavus starins involves the application of non-toxigenic strains to competitively exclude the toxigenic counterparts. Strain K49, a non-toxigenic strain isolated from a Mississippi corn field, is currently being tested in corn fields in the Mississippi Delta. However, little is known about the overall genetic diversity of A. flavus from year to year in corn fields and specifically in Mississippi. Our objective was to assess the temporal genetic variability of A. flavus isolates from different seasons, inoculum sources, and years, from a no-till corn field in Mississippi. The variability of the omtA gene was compared with the non-toxigenic strain K49. High levels of haplotypic diversity (24 omtA haplotypes; n=118; Hd=0.61±0.04) were found. Analysis of the norB-cypA gene region identified type I (1.5 kb) and type II (1.0 kb) deletion patterns from 74 and 97 A. flavus isolates, respectively. Despite the small sample size, two haplotypes were predominant in the overall population, H1 (n=71, 60%) and H49 (n=18, 15%). Haplotype 1 is a toxigenic isolate. Toxigenic isolates seem to be predominant in this natural population of isolates studied and atoxigenic isolates, as represented by H49, were less frequent.