Aspergillus

Aflatoxins are a family of toxic and carcinogenic secondary metabolites produced by five Aspergillus species from section Flavi: A. flavus, A. parasiticus, A. nomius, A. pseudotamarii and A. bombycis. Aspergillus flavus and A. parasiticus are the most extensively studied species because of their agricultural and medical importance.  Soil is the primary reservoir for A. flavus and A. parasiticus and they are frequently isolated from tropical and subtropical latitudes where they commonly infect peanut, corn, cottonseed and tree nuts.  Both species have affinities for oilseeds but differ in the types of aflatoxins produced.

While both A. flavus and A. parasiticus produce the B aflatoxins (B1 and B2), A. parasiticus also produces the G aflatoxins (G1 and G2), and is more frequently associated with peanuts than with cottonseed and corn.  Because of their high toxicity to humans and animals, federally and internationally mandated laws require the destruction or decontamination of the crop when the aflatoxin content exceeds 15 µg/kg, resulting in huge yield losses worldwide.  The degree of economic loss is worse under heat and drought conditions, which favor soil invasion and fungal growth.  Under these stress conditions, the contamination of peanuts, cottonseed and corn with A. flavus and A. parasiticus can be quite extensive and maintaining these agricultural commodities becomes a significant challenge.