Aflatoxin in maize: a review of the early literature from "moldy-corn toxicosis" to the genetics of aflatoxin accumulation resistance

Authors: Smith, Jesse; Williams, William; Windham, Gary

Submitted to: Mycotoxin Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/26/2018
Publication Date: 2/7/2019
Citation: Smith, J.S., Williams, W.P., Windham, G.L. 2019. Aflatoxin in maize: a review of the early literature from "moldy-corn toxicosis" to the genetics of aflatoxin accumulation resistance. Mycotoxin Research. 35:111-128. https://doi.org/10.1007/s12550-018-00340-w.
DOI: https://doi.org/10.1007/s12550-018-00340-w

Interpretive Summary: Aflatoxin is a potent toxin produced by Aspergillus flavus, a pathogen of corn (Zea mays L.). After infecting the developing ears of corn plants, A. flavus can contaminate the grain with aflatoxin. A major research focus of USDA-ARS corn breeders in the Southeast is to develop corn varieties that can resist infection by A. flavus and subsequent aflatoxin contamination. However, prior to the discovery of aflatoxin, A. flavus was considered only a minor corn pathogen and was not a priority for breeders. This article reviews the multi-disciplinary research that led to control of aflatoxin accumulation becoming a plant breeding objective. In 1957, “moldy corn” disease in the southeastern U.S. was shown to be associated with A. flavus. Aflatoxin was then discovered in 1961 after a poultry epidemic in England. In the early 1970’s, after surveying crops in the U.S. for aflatoxin contamination, corn grown in the Southeast proved to be especially vulnerable to contamination. The problem was originally thought of as occurring after harvest, but pre-harvest contamination was proven by 1975. The discovery of pre-harvest contamination meant genetically controlled host-plant resistance was a potential strategy to reduce aflatoxin in corn. The southeastern corn crop suffered epidemic aflatoxin contamination in 1977. In 1978 an experiment demonstrated that the differences in aflatoxin contamination between corn genotypes was under genetic control. These events combined to make breeding for resistance to aflatoxin contamination both a priority and a rational strategy. The USDA-ARS then initiated research into breeding corn to resist aflatoxin contamination in 1978 in Mississippi and in Georgia.

Technical Abstract: Aflatoxin is a potent toxin produced by Aspergillus flavus Link:Fr, an opportunistic ear-rot pathogen of maize (Zea mays L. subsp. Mays). Prior to the discovery of aflatoxin, A. flavus was considered a minor pathogen and was not a priority for maize breeders or pathologists. Aflatoxin was discovered in England in 1961 following an epidemic in poultry. By the early 1970s, surveys of agricultural commodities in the U.S. found that maize produced in the Southeast to be especially vulnerable to aflatoxin contamination. The problem was initially treated as a post-harvest issue, but pre-harvest contamination was proven by 1975. Pre-harvest contamination meant that genetically based host-plant resistance was a potential solution. The potential magnitude of the problem became apparent in 1977 when the southeastern maize crop suffered epidemic aflatoxin contamination. The first experiment demonstrating the heritability of host plant resistance to aflatoxin accumulation was published in 1978. These events combined to make breeding for reduced aflatoxin contamination both a high priority and a rational breeding objective. This review surveys the early scientific literature in order to place breeding maize for resistance to aflatoxin accumulation into its historical context. It tells the story of discoveries made by multi-disciplinary research that began with veterinary diseases of unknown etiology and resulted in resistance to a previously minor plant pathogen becoming a central public sector breeding objective.