Submitted to: American Phytopathological Society Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 4/18/2008
Publication Date: 7/15/2008
Citation: Wang, Z.; Liu, J.; Lee, R.D.; Scully B.; Guo, G. 2008. Postharvest Aspergillus flavus colonization in responding to preharvest field condition of drought stress and oligo-macroarray profiling of developing corn kernel gene expression under drought stress [abstract]. Proceedings from the American Phytopathological Society meeting, July 25-30, 2008, Minneapolis, MN.
Technical Abstract: Drought stress is a major factor known to contribute to preharvest aflatoxin contamination of maize kernels. Aspergillus flavus infection of maize kernels occurs earlier than aflatoxin accumulation in developing kernels. Recent studies have demonstrated higher concentration of defense or stress-related proteins in maize kernels of resistant genotypes compared with susceptible genotypes, suggesting that preharvest field condition influences gene expression differently in different genotypes resulting in different levels of “end product"-PR-proteins. Our goal is to study preharvest gene activities and effects on postharvest fungal colonization and aflatoxin production. The experiment was conducted in the field cages with irrigation system. Total 48 diverse inbreds were planted. Controlled pollination was done manually. Drought stress was imposed at 20 days after pollination (DAP) for stressed treatment. Immature ears were collected at 35 DAP for gene expression analysis. Mature ears were hand harvested and tested for postharvest A. flavus colonization and aflatoxin production in the laboratory. The fungal colonization of kernels and aflatoxin concentration suggest that preharvest drought stress could affect on postharvest host-A. flavus interactions differently in different genotypes, suggesting that different inbred lines with different levels of drought tolerance respond differently to the field condition. Preharvest drought stress increased or decreased postharvest fungal colonization and aflatoxin production. Gene expression analyses of preharvest developing kernels by using oligounclrodide macroarray of 211 genes identified 72 genes significantly up- or down- regulated by drought stress in comparison with irrigation. Sequences homology analysis showed 92% have known functions in constitutive or inducible defense mechanism, and only 8% with functions unrelated to defense or unknown. These results indicate that the genetics of individual line is different in response to drought stress, and maize plants not only regulate general stress-related genes, but also induce specific antifungal genes in reaction to the stress and result in the observed increased or decreased resistance response.