Biological control seen as aflatoxin remedy

Most peanut producers recognize the importance of reducing or eliminating aflatoxin in their crops. Less clear is how they should go about accomplishing this.

"We need to eliminate aflatoxin," says Joe Dorner, microbiologist with the National Peanut Research Laboratory in Dawson, Ga. "But in the near term, the best we probably can do is to reduce aflatoxin. This might be possible with the application of biological control technology that we've been working on for the past 13 to 14 years."

This biological control is achieved, he explains, by replacing the strains of aflatoxin found in the soil that make aflatoxin with strains that do not make aflatoxin.

"It's very simple. It's just a matter of taking the A. flavus in the field that makes aflatoxin and replacing it with A. flavus that doesn't make aflatoxin. This strain that doesn't make aflatoxin then dominates the soil environment.

"Whenever you have late-season drought conditions that predispose peanuts to aflatoxin contamination, your peanuts still will be infected by the fungus. However, it'll be a fungus that doesn't make aflatoxin, and the end result will be less aflatoxin in peanuts," says Dorner.

A typical peanut field will be dominated by the toxigenic strain of A. flavus by about a 20 to one margin over the non-toxigenic strains of aflatoxin, he says.

"Our goal is to try and displace a lot of these toxigenic strains by a preponderance of the non-toxigenic strain. We actually deliver these fungi on grain, such as barley. We make up this formulation in the laboratory, so we can treat several acres of peanuts or other crops.

"We associate the fungus that we want added to the field with the grain. Then, when we apply it to the field, it takes up moisture. The fungus grows and produces spores over the surface of the grain, and those spores are disseminated into the soil. This serves as the inoculum to get the fungus into the field."

Putting this relatively small amount of fungus out on the grain results in a large increase in the amount of fungus, notes Dorner. This allows the competition and displacement to occur, he adds.

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