Environmental influences on maize-Aspergillus flavus interactions and aflatoxin production

Authors: FOUNTAIN, JAKE - University Of Georgia; Scully, Brian; Ni, Xinzhi; KEMERAIT, ROBERT - University Of Georgia; LEE, R - University Of Georgia; CHEN, ZHI-YUAN - Louisiana State University; Guo, Baozhu

Submitted to: Frontiers in Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/21/2014
Publication Date: 1/27/2014
Citation: Fountain, J.C., Scully, B.T., Ni, X., Kemerait, R.C., Lee, R.D., Chen, Z., Guo, B. 2014. Environmental influences on maize-Aspergillus flavus interactions and aflatoxin production. Frontiers in Microbiology. doi: 10.3389/fmicb.2014.00040.

Interpretive Summary: Aspergillus flavus is the major producing fungus of aflatoxins worldwide in corn, peanuts, cottonseed, and other crops. Aflatoxins are highly carcinogenic and can be acutely toxic or fatal if ingested in sufficient quantities for both livestock and humans. Since the early 1960’s, this fungus has been the focus of intensive research due to the production of aflatoxins, particularly in the Southeast U.S. in the 1977 crop year, a severe aflatoxin outbreak in corn. A significant research effort has been put forth to determine the nature of the interaction occurring between Aflatoxin production, A. flavus, environment and its various hosts before harvest. Research has indicated that the interaction and overall resistance phenotype of the host is a quantitative trait with a relatively low heritability. In addition, a high degree of environmental interaction has been noted, particularly with sources of abiotic stress for either the host or the fungus such as drought or heat stress. Here, we review the history of research into this complex interaction and propose future directions for elucidating the relationship between resistance and susceptibility to A. flavus colonization, abiotic stress, and its relationship to oxidative stress in which aflatoxin production may function as a form of antioxidant protection to the producing fungus. Determining the role of oxidative stress in the regulation of aflatoxin biosynthesis as well as the role of host defenses against both A. flavus infection and mycotoxin biosynthesis are critical areas of research for the mitigation of aflatoxin contamination in corn and other crops

Technical Abstract: Since the early 1960’s, the fungal pathogen Aspergillus flavus (Link ex Fr.) has been the focus of intensive research due to the production of carcinogenic and highly toxic secondary metabolites collectively known as aflatoxins following pre-harvest colonization of crops. Given this recurrent problem and the occurrence of a severe aflatoxin outbreak in maize (Zea mays L.), particularly in the Southeast U.S. in the 1977 crop year, a significant research effort has been put forth to determine the nature of the interaction occurring between Aflatoxin production, A. flavus, environment and its various hosts before harvest. Many studies have investigated this interaction at the genetic, transcript, and protein levels, and in terms of fungal biology at either pre- or post-harvest time points. Later experiments have indicated that the interaction and overall resistance phenotype of the host is a quantitative trait with a relatively low heritability. In addition, a high degree of environmental interaction has been noted, particularly with sources of abiotic stress for either the host or the fungus such as drought or heat stress. Here, we review the history of research into this complex interaction and propose future directions for elucidating the relationship between resistance and susceptibility to A. flavus colonization, abiotic stress, and its relationship to oxidative stress in which aflatoxin production may function as a form of antioxidant protection to the producing fungus.