ARS | Publication request: Molecular Approaches to Development of Resistance to Preharvest Aflatoxin Contamination

Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: November 15, 2007
Publication Date: December 30, 2007
Citation: Bhatnagar, D., Rajasekaran, K., Cary, J.W., Brown, R.L., Yu, J., Cleveland, T.E. 2008. Molecular Approaches to Development of Resistance to Preharvest Aflatoxin Contamination. In: Leslie, J.F., Bandyopadhyay, R., and Visconti, A. (eds.) Mycotoxins: Detection Methods, Management, Public Health, and Agricultural Trade. Wallingford, Oxfordshire, UK:CABI Publishing. p. 257-276.

Technical Abstract: Mycotoxins are fungal metabolites that can contaminate foods and feeds and cause toxic effects in higher organisms that consume the contaminated commodities. Therefore, mycotoxin contamination of foods and feeds results is a serious food safety issue and affects the competitiveness of agricultural production in both domestic and export markets. Post-harvest management of these toxins in food and feed is only somewhat effective. Therefore, control of pre-harvest toxin contamination has received increased attention in the last decade, particularly the most economically relevant mycotoxins, namely aflatoxins produced by Aspergillus flavus, trichothecenes produced by various Fusarium spp and fumonisins produced by Fusarium verticillioides. Significant inroads have been made in establishing various pre-harvest control strategies, such as development of atoxigenic biocontrol fungi that can outcompete their closely related, toxigenic cousins in field environments, thus reducing levels of mycotoxins in the crops. Potential biochemical and genetic resistance markers have been identified in crops, particularly in corn, which are being utilized as selectable markers in breeding for resistance to aflatoxin contamination. Prototypes of genetically engineered crops have been developed which: (1) contain genes for resistance to the phytotoxic effects of certain trichothecenes, thereby helping reduce fungal virulence, or (2) contain genes encoding fungal growth inhibitors for reducing fungal infection. Gene clusters housing the genes governing formation of trichothecenes, fumonisins and aflatoxins have been elucidated and are being targeted in strategies to interrupt the biosynthesis of these mycotoxins. Recent advances in the genomics of the toxin producing fungi is providing significant information of host-fungal interactions and the molecular regulation of toxin production, as well as the field ecology of the fungus. Ultimately, a combination of strategies using biocompetitive fungi and enhancement of host-plant resistance may be needed to adequately prevent mycotoxin contamination in the field.