Evidence for an association in corn between stress tolerance and resistance to <i>Aspergillus flavus</i> infection and aflatoxin contamination

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 US, 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 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.

Key Words: Plant hormone, fungal infection, gene regulation, transcription factor.

African Journal of Biotechnology Vol.3(12) 2004: 693-699