Aflatoxin is a potent carcinogen produced in cottonseed infected by the fungus, Aspergillus flavus .
The aflatoxin content of cottonseed is strictly regulated. Seed lots with aflatoxin levels above 20 ppb cannot be sold for dairy feed and, thus, the economic value of contaminated cottonseed is greatly reduced. A. flavus is a soil-inhabiting fungus that lives off of decaying plant and animal debris. Recent research has shown that not all strains of A. flavus produce aflatoxin and that some strains producing little or no aflatoxin can competitively exclude aflatoxin-producing strains from cottonseed. The strain composition of the A. flavus community in the soil is very important in determining the potential for aflatoxin contamination of cottonseed.