Enhancing Inherent Fall Armyworm (Lepidoptera: Noctuidae) Resistance of Corn with Bacillus thuringiensis Genes

Abstract

Fall armyworm, Spodoptera frugiperda (J. E. Smith), is a serious pest of corn, Zea mays L., in the southern United States. Larvae feed extensively on leaves and other parts of the plant. Germplasm exhibiting a moderate level of resistance to leaf feeding damage has been identified and released. This germplasm has been used in breeding programs for developing corn hybrids with resistance to fall armyworm and other Lepidoptera. In recent years, much effort has also been devoted to developing corn hybrids with genes from Bacillus thuringiensis (Bt) that encode insecticidal proteins. Some of these hybrids have exhibited moderate resistance to fall armyworm damage. In this investigation hybrids with both native genetic resistance and genes from Bt encoding insecticidal proteins were evaluated for resistance to fall armyworm in field tests and laboratory bioassays. Hybrids with both types of resistance sustained less fall armyworm damage than hybrids that had only native genetic resistance or genes from Bt encoding insecticidal proteins alone. Larvae that fed on hybrids with both types of resistance were significantly smaller after feeding on plants in the field or on lyophilized whorl leaf tissue in a laboratory bioassay for 10 d than larvae fed on susceptible hybrids or hybrids with only one type of resistance. Both traditional host plant resistance and transformation of corn with genes from Bt provide hybrids with moderate levels of resistance, but when used together, they are complementary. Deployment of hybrids with both types of resistance should reduce losses to fall armyworm and also reduce the rate of buildups of resistance to Bt in fall armyworm populations.