Cross-Resistance to Bt Corn and Cotton in a Vip3A Resistant Strain of Fall Armyworm, Spodoptera Frugiperda

Transgenic crops producing Bacillus thuringiensis (Bt) have become a major tool for control of insect pests worldwide. Evolution of insect resistance to the Bt toxins has become a serious threat to the sustainability of this technology. Gene-pyramiding, combining two or more dissimilar Bt proteins in a crop has been used to delay insect resistance. However, the durability of gene-pyramiding can be reduced by cross-resistance. Resistance to Cry1F in the fall armyworm (FAW), Spodoptera fruigiperda (J.E. Smith), has occurred in the Southern U.S. Vip3A is a relatively new Bt protein with a different mode of action and has been introduced into almost all recently released Bt corn and cotton products. In this study, we provided the first documentation of cross crop resistance in FAW selected with Viptera 3111 corn (Vip3A+Cry1Ab) to multiple Bt corn and cotton products. Corn varieties used included SMT (Cry1F+Cry1A.105+Cry2Ab2), VT2P (Cry1A.105+Cry2Ab2), Viptera 3111 (Vip3A+Cry1Ab), HX (Cry1F), and Leptra (Cry1F+Vip3A). Cotton varieties include TL (Cry1Ab+Cry2Ae), TL+ (Cry1Ab+Cry2Ae+Vip3A), WS (Cry1Ac+Cry1F), WS3 (Cry1Ac+Cry1F+Vip3A), BG2 (Cry1Ac+Cry2Ab2), and BG3 (Cry1Ac+Cry2Ab2+Vip3A). Results generated from this study provided important information for insect pest management and resistance management of Bt crops.