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United States Department of Agriculture

Agricultural Research Service

Title: Effect of Application of Non-Toxigenic Strains of Aspergillus Flavus and A. Paraciticus on Subsequent Aflatoxin Contamination of Peanuts in Storage

Authors
item Dorner, Joe
item Cole, Richard - USDA,ARS RETIRED

Submitted to: Journal of Stored Products Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 3, 2001
Publication Date: N/A

Interpretive Summary: Aflatoxin contamination of peanuts is a serious problem for the producers of peanuts around the world. Contamination, which results from growth in peanuts by the molds, Aspergillus flavus and A. parasiticus, can occur in the field under drought conditions or in storage when peanuts are not maintained at safe moisture levels. Studies have shown that field contamination can be reduced by applying competitive, nontoxigenic strains of A. flavus and A. parasiticus to soil. In this two-year study, peanuts were treated with the nontoxigenic strains in the field, prior to storage, at both times, or neither time. Peanuts were then subjected to poor storage conditions that would be expected to lead to aflatoxin contamination. In the first year, non-contaminated peanuts were put in storage, but only peanuts that had been treated in the field remained essentially non- contaminated. In the second year, all peanuts were contaminated in the field, but biocontrol-treated peanuts contained 90% less aflatoxin than untreated peanuts. After storage, field-treated peanuts contained about 96% less aflatoxin than peanuts not treated in the field. Spraying peanuts prior to storage was not as effective at reducing aflatoxin contamination in storage as was treating peanuts in the field. Field application of the nontoxigenic strains had a carry-over effect and reduced aflatoxin contamination that occurred in storage.

Technical Abstract: A two-year study was conducted to determine the potential for biological control of aflatoxin contamination of peanuts during storage. Peanuts were treated in field plots by applying nontoxigenic strains of Aspergillus flavus and A. parasiticus, and after harvest, half the peanuts from both treated and control plots was sprayed with an aqueous conidial suspension containing the nontoxigenic strains. Peanuts were placed in separate compartments of a miniature warehouse and stored for 3-5 months under high temperature and relative humidity conditions. In 1998, peanuts were not contaminated with aflatoxin prior to storage. After storage, peanuts that were never treated with the competitive fungi contained an average of 78.1 ppb of aflatoxin. Peanuts not treated in the field but receiving the spray treatment before storage contained 48.8 ppb. Peanuts treated in the field only averaged 1.4 ppb, and peanuts treated both in the field and prior to storage contained 0.8 ppb. In 1999, peanuts suffered from late-season drought and were contaminated with aflatoxin at harvest, with controls averaging 516.8 ppb compared with 54.1 ppb in treated peanuts. After storage, non-field treated peanuts averaged 9145.1 ppb compared with 374.2 ppb for peanuts that had been field-treated, a 95.9% reduction. Field application of the nontoxigenic strains had a carry-over effect and reduced aflatoxin contamination that occurred in storage.

Last Modified: 7/24/2014
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