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

We used Agrobacterium tumefaciens to transform flowering stalk explant s of five genotypes of broccoli with a construct containing the neomyc in phosphotransferase gene and a Bacillus thuringiensis (Bt) gene [Cry IA(c) type] optimized for plant expression. Overall transformation eff iciency was 6.4%; 181 kanamycin-resistant plants were recovered. Of th e 162 kanamycin-resistant plants tested, 112 (69%) caused 100% moralit y of 1st-instar larvae of a Bt-susceptible diamondback moth strain. So uthern blots of some resistant transformants confirmed presence of the Bt gene. Selected plants that gave 100% mortality of susceptible larv ae allowed survival of a strain of diamondback moth that had evolved r esistance to Bt in the field. F-1 hybrids between resistant and suscep tible insects did not survive. Analysis of progeny from 26 resistant t ransgenic lines showed 16 that gave segregation ratios consistent with a single T-DNA integration. Southern analysis was used to verify thos e plants possessing a single T-DNA integration. Because these transgen ic plants kill susceptible larvae and F, larvae, but serve as a suitab le host for resistant ones, they provide an excellent model for tests of Bt resistance management strategies.