Friendly Fungus Helps Keep Aflatoxin Out ofCotton

In a brutal battle for food andspace, two fungal cousins are currently duking it out across the nation'scotton fields. Thanks to biological control strategies developed by theAgricultural Research Service (ARS), thebetter of these two microscopic relatives is winning.

Plant pathologistPeterCotty, who is part of theARSFood and Feed Safety Research Unit at New Orleans, La., but is located atthe University of Arizona-Tucson,instigated this competition. By pitting a benign strain of Aspergillusagainst its noxious kin, he's helping rid U.S. cotton of a harmful and costlytoxin.

While invisible and odorless, the Aspergillus fungi that Cotty isfocused on can churn out potent poisons called alfatoxins. These carcinogeniccompounds—linked to impaired growth, cancer and death—would threatenhuman health if stringent food safety standards, set by theU.S. Food and Drug Administration, weren't inplace to screen out contaminated products.

When cottonseed becomes infested with toxin-making fungi, it must bediscarded or severely downgraded. That's because the seed is a major feed ofdairy cows, and any toxins that might be present could transfer to the animals'milk. Every year, aflatoxin is responsible for ruining $3 million to $8 millionworth of cottonseed in the American Southwest.

Knowing that few control options exist for farmers, Cotty set out twodecades ago to find an environmentally sound and effective solution.Eventually, he discovered one, in the form of a benign strain of Aspergillusflavus that, when applied correctly to cotton fields, can outgrow andoutlive its more menacing cousins.

After years of rigorous studies with the strain, which is dubbed AF36, ARSobtained approval from the U.S. EnvironmentalProtection Agency in 1996 to test the new biocontrol in Arizona cottonfields.

At that time, only 120 acres of commercial cotton were treated with AF36.Now, more than 100,000 acres of U.S. cotton have been treated, greatly reducinglevels of harmful aflatoxins.

Readmore about the research in the August 2007 issue of AgriculturalResearch magazine.

ARS is the chief scientific research agency of theU.S. Department of Agriculture.