Submitted to: African Journal of Biotechnology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/15/2004
Publication Date: 12/29/2004
Citation: Chen, Z.-Y., Brown, R.L., Cleveland, T.E. 2004. Evidence for an association in corn between stress tolerance and resistance to Aspergillus flavus infection and aflatoxin contamination. African Journal of Biotechnology. 3(12):693-699. Interpretive Summary: Aflatoxins are poisons produced by the fungus Aspergillus flavus after it infects agricultural commodities, such as corn. Contamination of corn with aflatoxins causes financial loss to growers and is a potential health hazard to animals and humans. Field studies found that reducing drought stress through irrigation reduces aflatoxin contamination in corn and peanut, and that drought tolerant corn varieties produced significantly less aflatoxins in the field under drought conditions compared to aflatoxin-resistant lines. This suggests an association between stress-tolerance and aflatoxin resistance in corn. Evidence from genetic studies, and from studies comparing gene and protein expression showed that plant responses to drought and other stresses are similar to plant responses to pathogen infections. These studies also revealed that several common regulatory factors are involved in these responses. The presence of these common regulatory factors in response to drought or fungal infection could provide new approaches for increasing aflatoxin-resistance by enhancing plant tolerance to environmental stresses, such as drought. Providing drought tolerant corn lines to growers could prevent millions of dollars in losses due to aflatoxin contamination, as well as contribute to the safety of food and feed supplies.
Technical Abstract: Aflatoxins are carcinogenic secondary metabolites produced mainly by Aspergillus flavus during infection of susceptible crops, such as corn. A. flavus infection and subsequent aflatoxin contamination is a serious issue in the southern U.S., especially during a drought. Field studies demonstrate that reduction of drought stress by irrigation reduces aflatoxin contamination in corn and peanut. Drought tolerant corn varieties were also found to produce significantly less aflatoxins in the field under drought conditions compared to aflatoxin-resistant controls. Genetic studies to identify QTLs for low levels of aflatoxin accumulation also observed significant environmental effects on the location and number of QTLs between studies conducted at different locations and during different years. Proteomic comparisons of kernel proteins between corn genotypes resistant or susceptible to A. flavus infection have identified stress-related proteins along with antifungal proteins as associated with kernel resistance. Gene expression studies of plants in response to biotic or abiotic stress also found that disease resistance-related genes could be upregulated by abiotic stresses and vise versa. Further examination of host plant and pathogen interactions revealed that plant responses to abiotic stresses and pathogen infections were mediated through several common regulatory genes or factors. The presence of 'cross-talk' between responses to abiotic stress and biotic stress provides new approaches for enhancing host resistance to biotic stresses through the upregulation of key signal transduction factors.