Aflatoxins in Maize: A Mexican Perspective

Aflatoxins are carcinogenic metabolites produced by Aspergillus flavus, a fungal pathogen that infects maize both in the field and during storage. Mexico is the center of origin of maize and its production in most parts in the country is characterized by the employment of a wide diversity of open‐pollinated genotypes adapted to certain environments. In most regions, maize is produced under rain fed conditions with low fertilizer and pesticide input and consequent low yields, probably fostering A. flavus infection in drought‐stressed plants. In addition, poor pest control increases insect damage, facilitating fungal infection and aflatoxin contamination. Ideally, management of aflatoxin contamination should begin with the employment of resistant genotypes as has been demonstrated by several U.S. breeding programs. However, in Mexico the wide genetic diversity of maize has not been fully exploited to identify resistance to aflatoxin contamination in breeding programs, thus impeding the reduction of aflatoxin levels in the field. Additional complications come from the fact that transgenic maize expressing insecticidal protein or any other trait to reduce aflatoxin is not viable in Mexico due to a government prohibition on the use of genetically modified maize. Maize is a staple crop in Mexico with high consumption in forms such as tortillas; thus, aflatoxin contamination is a significant threat to human health. Although aflatoxins are partially destroyed during the alkaline cooking procedure (called nixtamalization) to prepare tortillas, residual levels of aflatoxins might be considerable. Although important research has been conducted in several aspects of aflatoxin contamination of maize by universities, agricultural centers, and some government agencies, a full mycotoxin research program is needed in Mexico to ascertain the extents of aflatoxin contamination in different parts of the country and to develop economically viable technology to reduce aflatoxin exposure.