Mycotoxin Research Vol. 22, No. 2 (2006), 118-124 Prevention of preharvest aflatoxin contamination through genetic engineering of crops K. Rajasekaran, J.W. Cary, T. E. Cleveland U.S. Department of Agriculture, Agricultural Research Service, Southern Regional Research Center, New Orleans, Louisiana 70124, USA Abstract Current practices on prevention of aflatoxin contamination of crop species include time consuming, expensive agronomic practices. Of all the methods available to-date, conventional breeding and/or genetic engineering to develop host plant-based resistance to aflatoxin-producing fungi appear to be valuable for several reasons. However, breeding for disease-resistant crops is very time consuming, especially in tree crops, and does not lend itself ready to combat the evolution of new virulent fungal races. Moreover, availability of known genotypes with natural resistance to mycotoxin-producing fungi is a prerequisite for the successful breeding program. While it is possible to identify a few genotypes of corn or peanuts that are naturally resistant to Aspergillus we do not know whether these antifungal factors are specific to A. flavus. In crops like cotton, there are no known naturally resistant varieties to Aspergillus. Availability of transgenic varieties with antifungal traits is extremely valuable as a breeding tool. Several antifungal proteins and peptides are available for genetic engineering of susceptible crop species, thanks to the availability of efficient modern tools to understand and evaluate protein interactions by proteomics of host, and genomics and field ecology of the fungus. Transgenic approaches are being undertaken in several industry and academic laboratories to prevent invasion by Aspergillus fungi or to prevent biosynthesis of aflatoxin. Recent trends in reducing aflatoxin contamination through genetic engineering of cultivated crop species with antifungal proteins are summarized in this report. Keywords: aflatoxin prevention, antifungal proteins, biotechnology, disease resistance, genetic engineering, peptides, transgenic crops Introduction Aspergillus flavus and A. parasiticus, that produce aflatoxin in several crop species including cotton, peanuts, tree nuts and corn, are not true plant pathogens but opportunistic, saprophytic fungi. Defense mechanisms elicited in affected crop plants are not specific to these saprophytic fungi. At present, disease manage- ment in crop fields is practiced solely through adaptation of suitable cultural practices such as rotation, use of quality seed and fungicides and altering the time of planting (1). In addition to postharvest procedures through use of chemicals for aflatoxin prevention, several other viable means to prevent the contamination process in crops before harvest are being undertaken in Presented at the EU-USA Bilateral Workshop on Toxigenic Fungi & Mycotoxins, New Orleans, USA, July 5-7, 2005 Correspondence: K. Rajasekaran, Food and Feed Safety Research Unit, USDNARS/SRRC, 1100 Robert E. Lee Boulevard, New OrLeans, Louisiana 70124 USA (krajah@srrc.ars.usda.gov) several laboratories around the world (1-5). These technologies include use of resistant germplasm to breed for resistant varieties, biological control through the use of atoxigenic strains to compete and replace toxigenic strains in the field, and enhancement of resistance in crops through genetic engineering. The later strategy is especially pertinent to cottonseed, which does not possess practical levels of natural resistance to aflatoxin producing fungi in its germplasm base. Conventional breeding for disease-resistant crops, especially perennial crops, is very time consuming and does not lend itself ready to combat the evolution of new virulent fungal races. The steady unraveling of complex interactions between fungal pathogens such as Aspergilli and host plants has already paved the way for production of transgenic disease resistant crop plants (6-9). Transgenic approaches are being undertaken in several industry and academic laboratories to prevent invasion by Aspergillus fungi or to prevent biosynthesis of aflatoxin. We summarize here the recent trends in reducing aflatoxin 118