Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 23, 2008
Publication Date: April 1, 2009
Citation: Dorner, J.W. 2009. Biological Control of Aflatoxin Contamination in Corn using a Nontoxigenic Strain of Aspergillus flavus. Journal of Food Protection. 2009. V.72 pp 801-804. Interpretive Summary: Aflatoxin contamination of crops compromises the safety of food and feed supplies and causes significant economic losses each year. Aflatoxin contamination can occur when crops are infected with aflatoxin-producing strains of Aspergillus flavus and A. parasiticus, molds that are relatively abundant in agricultural soils. Afla-guard is a product that has been developed in recent years by ARS for biological control of aflatoxin contamination. Its mode of action is to establish a dominant soil population of a nontoxigenic strain of A. flavus that displaces toxigenic strains during crop infection. Afla-guard has been approved by the U. S. Environmental Protection Agency for use on peanuts and is now being used commercially. The purpose of this two-year study was to determine the efficacy of the nontoxigenic strain when applied to corn under three different scenarios. First, afla-guard was applied to soil when corn plants were about 0.8 m tall. Second, afla-guard was applied to the whorls of plants immediately prior to tasseling. Third, the nontoxigenic strain of A. flavus was applied as spores in a liquid spray four times during silking. Results showed that all applications significantly reduced aflatoxin contamination in the second year of the study, with the whorl application producing the greatest reduction. Results were somewhat compromised by the high incidence of the nontoxigenic strain in the untreated, control corn. Nevertheless, results show potential for reducing aflatoxin in corn through application of the nontoxigenic strain with afla-guard.
Technical Abstract: A two-year study was conducted to determine the efficacy of different applications of a nontoxigenic strain of Aspergillus flavus for reducing aflatoxin contamination in corn. Treatments consisted of the nontoxigenic strain in the form of 1) conidia-coated hulled barley applied to soil when corn was about 0.8 m tall; 2) conidia-coated hulled barley applied in plant whorls prior to tasseling; 3) multiple applications of a liquid spray formulation of conidia during silking; and 4) untreated control. Treatments were replicated eight times in individual plots consisting of four rows of 18 m. In year one no significant differences were associated with treatments for aflatoxin, total A. flavus colonization, or incidence of nontoxigenic isolates of A. flavus in corn, which were all relatively high ranging from 83.8 to 93.1%. In year two the whorl application produced a significantly lower mean aflatoxin concentration of 49.5 ppb compared with all other treatments while both the soil (108.3 ppb) and spray applications (173.7 ppb) were significantly reduced compared with control (191.6 ppb). The whorl application was the only treatment that had a significantly higher incidence (86.5%) of nontoxigenic isolates of A. flavus than control, which was still relatively high at 69.1%. Data indicated that applications of the nontoxigenic strain influenced untreated corn, thus reducing the apparent effect of the biocontrol treatments. Larger scale studies with greater separation between treated and untreated fields is warranted.