TRANSGENIC BROCCOLI EXPRESSING A BACILLUS-THURINGIENSIS INSECTICIDAL CRYSTAL PROTEIN - IMPLICATIONS FOR PEST RESISTANCE MANAGEMENT STRATEGIES

We used Agrobacterium tumefaciens to transform flowering stalk explants of five genotypes of broccoli with a construct containing the neomycin phosphotransferase gene and a Bacillus thuringiensis (Bt) gene [CryIA(c) type] optimized for plant expression. Overall transformation efficiency was 6.4%; 181 kanamycin-resistant plants were recovered. Of the 162 kanamycin-resistant plants tested, 112 (69%) caused 100% morality of 1st-instar larvae of a Bt-susceptible diamondback moth strain. Southern blots of some resistant transformants confirmed presence of the Bt gene. Selected plants that gave 100% mortality of susceptible larvae allowed survival of a strain of diamondback moth that had evolved resistance to Bt in the field. F-1 hybrids between resistant and susceptible insects did not survive. Analysis of progeny from 26 resistant transgenic lines showed 16 that gave segregation ratios consistent with a single T-DNA integration. Southern analysis was used to verify those plants possessing a single T-DNA integration. Because these transgenic plants kill susceptible larvae and F, larvae, but serve as a suitable host for resistant ones, they provide an excellent model for tests of Bt resistance management strategies.