Submitted to: Journal of Food Additives & Contaminants
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/15/2009
Publication Date: 5/10/2010
Citation: Donner, M., Atehnkeng, J., Sikora, R.A., Bandyopadhyay, R., Cotty, P.J. 2010. Molecular Characterization of Atoxigenic Strains for Biological Control of Aflatoxins in Nigeria. Journal of Food Additives & Contaminants. 27(5):576-590. Interpretive Summary: Aflatoxins are toxic fungal metabolites that can inhibit human development, cause cancer, and even induce death. Preventing the occurrence of these toxins in foods is very difficult, but of great concern in West Africa. The use of strains of Aspergillus flavus that do not produce aflatoxins to competitively exclude aflatoxin-producers has become widely accepted as a useful component of aflatoxin management programs. Using DNA sequence, the current study characterized eighteen non-aflatoxin producing A. flavus isolates native to Nigeria. These isolates are currently being developed as tools for limiting contamination in Africa. The sequence information developed provides both insight into the relative stability of the non-aflatoxin production and a basis for rapid molecular monitoring of the atoxigenic VCGs in the environment. The current study demonstrates VCGs of A. flavus in West Africa with diverse mechanisms of lost aflatoxin production and with potential value in aflatoxin management programs.
Technical Abstract: Aflatoxins are highly toxic, carcinogens produced by several species in Aspergillus section Flavi. Strains of A. flavus that do not produce aflatoxins, called atoxigenic strains, have been used commercially in North America as tools for limiting aflatoxin contamination. A similar aflatoxin management strategy is being pursued in Nigeria. Initial efforts in Nigeria have focused on 18 atoxigenic A. flavus Vegetative Compatibility Groups (VCGs). Loci across the 68 kb aflatoxin biosynthesis gene cluster were compared among the 18 atoxigenic VCGs from Nigeria and aflatoxin producers. Five of the VCGs from Nigeria had large deletions (37kb to 65kb) extending from the teleomeric side of the aflatoxin biosynthesis cluster. In one VCG (AV0222) the deletion extended through the cluster to the adjacent sugar cluster. The remaining twelve atoxigenic VCGs, including the VCG used for aflatoxin management in North America, contained all of the aflatoxin pathway genes. However, none of the African VCGs had the SNP known to cause atoxigenicity in the North American VCG. The data support multiple, independent origins of atoxigenicity and reflect diversity among atoxigenics that might be exploited during selection of VCGs for biocontrol of aflatoxin contamination.