Submitted to: Journal of Food Additives & Contaminants
Publication Type: Abstract Only
Publication Acceptance Date: 5/22/2007
Publication Date: 4/15/2008
Citation: Abbas, H.K., Zablotowicz, R.M., Bruns, H.A., Abel, C.A. 2008. Development of non-toxigenic strains of aspergillus flavus for control of aflatoxin in corn. Journal of Food Additives & Contaminants. 7:181-192
Technical Abstract: Aflatoxin is a major economic and toxicological problem in Mississippi Delta maize (Zea mays L.) and throughout the Southern United States. In 1998, this problem was particularly severe, resulting in significant losses of the maize crop due to high levels of contamination. Aflatoxin is produced by Aspergillus flavus, and particularly in hot, dry weather conditions. Although there has been considerable research effort directed at reducing aflatoxin contamination in maize, no consistent or reliable control methods are yet available. In peanuts and cotton, the use of A. flavus isolates which do not produce aflatoxin offers potential in reducing aflatoxin contamination. Initially we conducted a survey of A. flavus isolates from Mississippi Delta soil, maize, rice and peanuts and observed that 36% of more than 500 isolates produced less than 20 ppb of aflatoxin. We also observed that isolates which did not produce sclerotia were much less likely to be toxigenic than isolates that produced large sclerotia. From this research, two non-toxigenic strains (K49 and CT3) that suppress aflatoxin when applied to maize as soil inoculants were identified. Over four years of field testing, these non-toxigenic isolates reduced aflatoxin contamination of maize by 60-94%. Following several years of application to maize, the non-toxigenic strains tend to displace toxin-producing isolates. K49 may be a more suitable biocontrol agent than CT3 based on several factors. Although neither isolates produces aflatoxin, strain K49 also does not produce cyclopiazonic acid. In relation to colonization potential of maize and soil, K49 grows faster than CT3 and forms sclerotia, while CT3 does not. We assessed fungal colonization of maize using a pin bar inoculation technique. In two years of testing, K49 showed more rapid colonization of maize than CT3. Studies are in progress to refine delivery techniques for nontoxigenic A. flavus strains in maize, to improve efficiency in reducing aflatoxin contamination and to increase potential for commercial development.