Protection from stored grain insects using transgenic maize hybrids and implications for Aspergillus flavus and aflatoxin contamination

Transgenic insect -resistant maize has been assessed thoroughly in the field but not in storage. The effects of several transgenic Bacillus thuringiensis (Bt) maize hybrids on the interactions between stored -grain insects (Indianmeal moth, Plodia interpunctella, or maize weevil, Sitophilus zeamais) and the storage fungus Aspergillus flavus were evaluated in this study under laboratory conditions. Grain of Bt and non -Bt maize hybrids, with or without the conidia of A. flavus, were infested with P. interpunctella larvae or S. zeamais adults separately and stored at 32 degrees C and 80-85 % relative humidity. In Bt maize hybrids with lepidopteran resistance genes expressing Cry1Ab, Cry1Ab x Cry1F, and Cry1Ab x Cry1F x Vip3Aa proteins, the mortality of P. interpunctella was 100 % at the end of the 28 -day storage period. In Bt hybrids with coleopteran resistance genes expressing mCry3A and mCry3A x Cry34A/35Ab1 proteins, mortality of S. zeamais was 100 %. In the non -Bt grain, aflatoxin levels at the end of the storage period increased by almost two -fold in the presence of either P. interpunctella or S. zeamais (p <= 0.01). Insect infestation did not enhance A. flavus or aflatoxin contamination on transgenic hybrids because of deterred insect activity. In the non -Bt hybrid, A. flavus caused increased mortality, reduced survivorship, and lower growth indices of both insects, limiting their feeding in the A. flavus coated conventional grain. As a result, insect damage and grain weight loss were significantly higher in the absence of A. flavus. Insect infestation only enhanced aflatoxin contamination in the absence of transgenic insect resistance genes. This study demonstrated that Bt proteins were effective against the stored -grain insects P. interpunctella and S. zeamais and suggests that the use of transgenic hybrids can mitigate the risk of insect infestation, and A. flavus and aflatoxin contamination in stored grain.