IDENTIFICATION AND ENHANCEMENT OF SEED-BASED BIOCHEMICAL RESISTANCE IN CROPS TO AFLATOXIN PRODUCING PATHOGENS
Location: Food and Feed Safety Research
Title: Transgenic approaches for pre-harvest control of mycotoxin contamination in crop plants
Submitted to: World Mycotoxin Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 15, 2009
Publication Date: May 4, 2009
Citation: Cary, J.W., Rajasekaran, K., Yu, J., Brown, R.L., Bhatnagar, D., Cleveland, T.E. 2009. Transgenic approaches for pre-harvest control of mycotoxin contamination in crop plants. World Mycotoxin Journal. 2(2):203-214.
Interpretive Summary: Control of preharvest mycotoxin contamination of susceptible crops such as corn, wheat, barley, cotton, and peanut is possible through time consuming and expensive agronomic practices. Breeding for disease-resistant crops is also very time consuming and does not lend itself readily to combat the evolution of new virulent fungal races. More over, availability of known genotypes with natural resistance to mycotoxin-producing fungi is a prerequisite for the successful breeding program. It is possible to identify a few genotypes of corn or wheat that are naturally resistant to mycotoxigenic fungi but in crops like cotton, there are no known naturally resistant varieties to toxigenic fungi like Aspergillus. So far, the best options available to us are through biocontrol and/or genetic engineering. Availability of transgenic varieties with antifungal or anti-toxin traits is extremely valuable as a breeding tool. Use of fungicides or chemicals is costly and can add to the cost of production. Moreover, the growing concerns regarding environmental safety and ground water quality demand less dependence on agrochemicals. Disease resistant transgenic crops would not only control mycotoxin-producing organisms such as A. flavus, A. parasiticus and Fusarium spp. but also several microbial (fungal, bacterial and viral) diseases which cause significant economic losses in crop production. This review explores recent advances regarding genetic engineering approaches towards the control of mycotoxin contamination using native and heterologous genes.
Mycotoxins are fungal metabolites that can contaminate food and feed crops worldwide and are responsible for toxic effects in animals and humans that consume contaminated commodities. Regulatory guidelines and limits for mycotoxins have been set by the U.S. Food and Drug Administration (FDA) and food safety agencies of other countries for both import and export of affected commodities. Mycotoxin contamination of foods and feeds can also cause serious economic hardships to producers, processors, and the consumer. Therefore, there has been a concerted effort by researchers worldwide to develop strategies for the effective control of mycotoxin contamination of crops, particularly at the pre-harvest stage. Strategies currently being utilized to combat pre-harvest mycotoxin contamination include: i) use of non-toxigenic biocontrol strains; ii) improved agricultural practices; iii) application of agrochemicals; iv) plant breeding for resistance; and v) genetic engineering of resistance genes into crop plants. This article highlights research on the genetic engineering of plants for resistance to invasion by mycotoxigenic fungi as well as detoxification of mycotoxins. Emphasis is placed on the most economically relevant fungi and the mycotoxins they produce. These include aflatoxins produced mainly by Aspergillus flavus and A. parasiticus, trichothecenes produced mainly by Fusarium graminearum, and to a lesser extent, fumonisins produced by Fusarium verticillioides. Information is also presented on the use of genomics and proteomics technologies as a means of identifying genes and proteins that can be utilized in transgenic approaches to control the growth of mycotoxigenic fungi and the mycotoxins that they produce in food and feed crops.