Submitted to: Crop Protection Journal
Publication Type: Book / chapter
Publication Acceptance Date: 4/1/2008
Publication Date: 6/4/2008
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 maize.. Crop Protection Journal. 7:181-192 Interpretive Summary: Aflatoxin, caused by the mold Aspergillus flavus, is a continuing problem challenging corn production in the Mid South area of the United States. Biological control using non toxin producing strains of this mold to compete against natural toxin producing molds is an attractive and scientifically sound approach. This manuscript describes the accomplishments of the Stoneville ARS team in evaluating several approaches to control this problem. The ecology of this mold in the Mississippi Delta corn-cotton production system has been characterized. From these ecological studies, strains of this mold capable for reducing aflatoxin contamination of corn have been identified and their efficiency demonstrated in several years of field trials. If this concept is successfully commercialized, it should provide an economic opportunity for increased profit in Southern US corn production.
Technical Abstract: Aflatoxin (AF), produced by Aspergillus flavus, can be a major problem in Mississippi Delta maize (Zea mays L.) causing economic losses if levels of contamination are high. Although research has been directed at reducing maize AF contamination, no consistent control methods are available. This manuscript summarizes research approaches in development of non-aflatoxigenic A. flavus strains to control maize AF contamination. In a survey of A. flavus isolates from Mississippi Delta soil, 36% of 517 isolates produced less than 20 ppb of aflatoxin. This survey identified two non-toxigenic strains (K49 and CT3) that, when applied to maize as soil inoculants, suppress AF by competitive displacement. Four years of field testing showed these non-toxigenic isolates reduced AF contamination by 60-94%. The non-toxigenic strains displace the toxigenic A. flavus populations in soil. K49 may be a more suitable biocontrol agent than CT3 because K49 also does not produce cyclopiazonic acid. K49 has greater soil colonization potential, based on fast growth and sclerotia formation, than does CT3. Using a pinbar inoculation technique, K49 displayed a more rapid maize colonization than CT3. These results suggest the basic method for reducing AF contamination is by competitive exclusion. Further work to improve biocontrol efficacy in reducing AF contamination is in progress.