United States Department of Agriculture-Agricultural Research Service research on pre-harvest prevention of mycotoxins and mycotoxigenic fungi in US crops

Abstract

Mycotoxins (ie toxins produced by molds) 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 US agriculture in both domestic and export markets. This article highlights research accomplished by Agricultural Research Service (ARS) laboratories on control of pre-harvest toxin contamination by using biocontrol, host-plant resistance enhancement and integrated management systems. Emphasis is placed on the most economically relevant mycotoxins, namely aflatoxins produced by Aspergillus flavus, Link, trichothecenes produced by various Fusarium spp and fumonisins produced by F verticillioides. Significant inroads have been made in establishing various 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. 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. To achieve this, plants may be developed that resist fungal infection and/or reduce the toxic effects of the mycotoxins themselves, or interrupt mycotoxin biosynthesis. This research effort could potentially save affected agricultural industries hundreds of millions of dollars during years of serious mycotoxin outbreaks.