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United States Department of Agriculture

Agricultural Research Service

Title: Biological Control of Aflatoxin Contamination of Crops

Author
item Dorner, Joe

Submitted to: Journal of Toxicology Toxins Reviews
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 15, 2004
Publication Date: August 31, 2004
Citation: -

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. One promising strategy to prevent aflatoxin contamination is biological control that is achieved by applying a strain of A. flavus to soil that cannot produce aflatoxin. When a very competitive, nontoxigenic strain of A. flavus is applied to soil, it competitively excludes the toxigenic strains and preferentially infects the susceptible crop, such as peanuts. But even though the crop is infected, aflatoxin contamination does not result because the infecting strain cannot produce the toxin. Various formulations have been used to apply the nontoxigenic strain to soil, but the most effective methods have been to combine the desired strain with a carrier/substrate, such as a small grain. This was done either by minimally growing the desired strain on sterilized grain or by coating the surface of the grain with spores of the strain. After application to the field and uptake of moisture, the mold completely colonizes the grain and produces abundant spores that are released into the soil to compete with those of the toxin producers. Significant reductions in aflatoxin contamination have been achieved consistently in peanuts and cottonseed. Efforts are underway to commercialize the process and make this aflatoxin-reducing technology widely available.

Technical Abstract: Aflatoxin contamination of crops compromises the safety of food and feed supplies and causes significant economic losses each year. Of the many research approaches being studied to reduce and, ultimately, eliminate aflatoxin contamination, biological control is one of the more promising, particularly for the near-term. Numerous organisms have been tested for biological control of aflatoxin contamination including bacteria, yeasts, and nontoxigenic strains of the causal organisms, Aspergillus flavus and A. parasiticus. Most of the field successes to date have been achieved by applying certain nontoxigenic strains of A. flavus and A. parasiticus to soil of susceptible crops, such as peanuts, cotton, and corn. The applied strains occupy the same niche as the naturally-occurring toxigenic strains and competitively exclude them when crops are susceptible to infection. Various formulations have been used to apply the nontoxigenic strains to soil, but the most effective methods have been to combine the desired strain with a carrier/substrate, such as a small grain. This was done either by minimally growing the desired strain on sterilized grain or by coating the surface of the grain with conidia of the strain. After application to the field and uptake of moisture, the fungus completely colonizes the grain, and abundant sporulation provides inoculum levels sufficient to achieve a competitive advantage for the nontoxigenic strain. In several years of field studies, particularly with peanuts and cotton, significant reductions in aflatoxin contamination in the range of 70-90% have been achieved consistently. Efforts are underway to commercialize the process and make this aflatoxin-reducing technology widely available.

Last Modified: 12/21/2014
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