AF36 Objectives

Reduce aflatoxin-producing fungi in soil.

Summary

Aflatoxin contamination of cottonseed and other commodities such as corn, pistachios, almonds and figs has, for decades, created a major negative impact on agriculture in Arizona and other southwestern and western states. In order to ensure a healthy food supply in the United States, crops cannot enter select markets if contamination exceeds regulatory limits. Widespread aflatoxin contamination results in sizable annual revenue losses to each of these industries each year.

Technical Review

Aflatoxins are a group of toxic, carcinogenic fungal metabolites produced by specific isolates of Aspergillus flavus. Concern for human and animal health has led to the establishment of regulatory limitations on the quantity of aflatoxins permitted in foods and feeds throughout the world. Aflatoxin contamination creates serious problems for the United States cottonseed industry. This is due to the ability of dairy cattle to readily transmit aflatoxins from feed to milk in slightly modified form. In order to ensure a healthy food supply in the United States, laws prohibit the aflatoxin content of milk from exceeding 0.5 ppb. To ensure this level, cottonseed and corn fed to dairy cattle is mandated to contain less than 20 ppb. Overseas, aflatoxin controls are frequently more stringent than in the U.S. Thus, aflatoxin content can limit export of commodities and aflatoxin regulations can serve as non-tariff barriers to trade. The desert southwest and particularly Arizona is at a serious disadvantage in this area due to aflatoxin.

The fungal isolate AF36 is an atoxigenic member of the species Aspergillus flavus that has been shown to have the ability to competitively exclude aflatoxin-producing fungi and thereby reduce aflatoxin contamination of cottonseed and corn. In greenhouse, field-plot, and commercial field tests, the efficacy of Aspergillus flavus AF36 has repeatedly been demonstrated. Results to date suggest that applications of AF36 reduce the average aflatoxin producing potential of fungal communities within both the treated and nearby fields. Treatments also have been shown to cause long-term reductions in the average aflatoxin producing potential of fungi in treated fields and in so doing provide the opportunity to reduce contamination throughout entire treatment areas and extending beyond treated areas.

Relevance Statement

Mycotoxins have cost USA crop producers annual losses ranging between $300 million and $1.7 billion. Crops containing over 20 ppb of aflatoxin cannot be fed to dairy cows, leading to a large economic loss to the producer.

Facilities and Equipment

The Arizona Cotton Research & Protection Council has two fully equipped laboratories; one for manufacturing and quality control of atoxigenic strain inoculum and one for conducting soil, crop and air sample fungal evaluation.

Field sampling activities necessary to generate soil, crop and air samples for fungal analyses are organized through six district supervisors working out of five field offices geographically located throughout Arizona’s cotton grower regions.