Submitted to: International Cotton Advisory Committee Recorder
Publication Type: Book / chapter
Publication Acceptance Date: 8/10/2010
Publication Date: 10/5/2010
Citation: Garber, N.P., Wakelyn, P.J., Cotty, P.J. 2010. Biocompetitive control of aflatoxin in cotton: mycotoxin management in the 21st century. In: Wakelyn, P.J., Chaudhry, M.R., editors. Cotton: Technology for the 21st Century. 1st edition. Washington, DC: International Cotton Advisory Committee. p. 181-201. Interpretive Summary: Aflatoxins are toxic fungal metabolites that can inhibit human development, cause cancer, and even induce death. The most important cause of aflatoxin contamination is the fungal species Aspergillus flavus. Some strains of A. flavus produce no aflatoxins and are called atoxigenic. Atoxigenic strains are being developed as biological agents for limiting aflatoxin contamination. Several types of management strategies are being developed based on atoxigenic strains. One of these utilizes atoxigenic strains to make relatively long-term changes to fungal communities in agricultural areas and in so doing reduce the vulnerability of all crops grown in that area to aflatoxin contamination. This type of biological control offers the potential to reduce the burden of aflatoxin contamination on the sustainability of agricultural enterprise in several regions of the United States. Grower-controlled approaches have led the development of biocontrol technology especially in cotton. The advances in biocontrol of aflatoxin will open new and more valuable markets to cottonseed, as it is seen as a high value source of human and animal nutrition.
Technical Abstract: Aflatoxins are highly toxic Aspergillus metabolites that cause immune-system suppression, growth retardation, cancer, and death in both humans and domestic animals. Aflatoxin contamination of cottonseed can erode crop profitability at concentrations as low as 20 'g/kg. Processing of cottonseed for oil concentrates aflatoxin in the residual meal which is normally a value protein source. Aflatoxin producing fungi have considerable intraspecific variability and the species that causes most aflatoxin contamination of crops, A. flavus, varies widely in aflatoxin production with some individuals producing no aflatoxins (atoxigenic). Biocontrol strategies for reducing aflatoxin contamination have been developed that utilize atoxigenic strains of A. flavus to competitively exclude aflatoxin producers. In commercial practice, atoxigenic strains are applied during crop development on a nutrient source that fuels initial reproduction and dispersal of the biocontrol agent. Although applications alter the composition of A. flavus communities associated with crops and, as a result, reduce crop aflatoxin content, both crop infection by A. flavus and the quantity of A. flavus on the crop at harvest are no different in treated compared to untreated crops. Long-term influences of atoxigenic strain treatments have led to efforts to develop area-wide aflatoxin management programs. For optimal benefits, improved methods for utilizing atoxigenic strains must be envisioned and developed. This likely will include methods that simultaneously utilize multiple, locally adapted atoxigenic strains. In most of the developed world economic incentives to manage aflatoxins in cottonseed are lacking. However, biocontrol in cotton can result in carried over benefits to staple crops either rotated with or grown in close proximity to cotton. Biocontrol programs in cotton have included projects where grower-governed organizations manufacture and distribute the biocontrol agent and then assess the efficacy. To date, grower-controlled approaches allow for lowest cost access to aflatoxin management.