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United States Department of Agriculture

Agricultural Research Service

Title: Evaluation of Biological Control Formulations to Reduce Aflatoxin Contamination in Peanuts

Authors
item Dorner, Joe
item Cole, R - RETIRED USDA
item Connick, W - RETIRED USDA
item Daigle, Donald
item Mcquire, M - USDA
item Shasha, B - DECEASED

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 17, 2002
Publication Date: December 1, 2003
Citation: -

Interpretive Summary: Aflatoxin contamination of peanuts is a serious food safety issue, and it threatens the economic viability of the U. S. peanut industry. Aflatoxin contamination results from growth in peanuts by Aspergillus flavus and A. parasiticus, fungi that occur naturally in soils. Application of strains of A. flavus and A. parasiticus that cannot make aflatoxin (nontoxigenic strains) to peanut soils has proven effective in significantly reducing aflatoxin contamination of peanuts. The purpose of this study was to evaluate various formulations that might be used to inoculate soils with these nontoxigenic strains. Formulations included: (1) sterile rice on which the nontoxigenic strains were grown (SSF rice); (2) fungal spores extruded in a wheat gluten-kaolin matrix (Pesta); (3) fungal spores encapsulated in pregelatinized corn flour granules. Formulations were applied to peanut plots in 1996 and reapplied to the same plots in 1997. Results showed that all formulations established a large soil population of the nontoxigenic strains for competition with naturally-occurring strains. The percentage of peanuts infected by aflatoxin-producing strains of A. flavus and A. parasiticus was significantly reduced in year one by SSF rice and corn flour granules and in year two by SSF rice. Aflatoxin reductions in year one for all formulation treatments averaged eighty six percent, but they were not statistically significant because of wide variation in the untreated controls. In year two, aflatoxin concentrations in peanuts were significantly reduced by all formulation treatments with an average reduction of ninety two percent. Each of the formulations tested was effective in delivering competitive levels of nontoxigenic strains of A. flavus and A. parasiticus to soil and in reducing subsequent aflatoxin contamination of peanuts.

Technical Abstract: A two-year study was conducted to evaluate the efficacy of three formulations of nontoxigenic strains of Aspergillus flavus and A. parasiticus to reduce preharvest aflatoxin contamination of peanuts. Formulations included: (1) solid-state fermented rice; (2) fungal conidia encapsulated in an extrusion product termed Pesta; (3) conidia encapsulated in pregelatinized corn flour granules. Formulations were applied to peanut plots in 1996 and reapplied to the same plots in 1997 in a randomized design with four replications, including untreated controls. Analysis of soils for A. flavus and A. parasiticus showed that a large soil population of the nontoxigenic strains resulted from all formulations. In the first year, the percentage of kernels infected by wild-type A. flavus and A. parasiticus was significantly reduced in plots treated with rice and corn flour granules, but it was reduced only in the rice-treated plots in year two. There were no significant differences in total infection of kernels by all strains of A. flavus and A. parasiticus in either year. Aflatoxin concentrations in peanuts were significantly reduced in year two by all formulation treatments with an average reduction of 92%. Reductions were also noted for all formulation treatments in year one (average 86%), but they were not statistically significant because of wide variation in the aflatoxin concentrations in the untreated controls. Each of the formulations tested, therefore, was effective in delivering competitive levels of nontoxigenic strains of A. flavus and A. parasiticus to soil and in reducing subsequent aflatoxin contamination of peanuts.

Last Modified: 10/24/2014
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