Survival, development, and oviposition of resistant diamondback moth (Lepidoptera : Plutellidae) on transgenic canola producing a Bacillus thuringiensis toxin

We measured responses of diamondback moth, Plutella xylostella L., to trans genic and nontransgenic canola, Brassica napus L. Transgenic canola express ed a cry1Ac gene of Bacillus thuringiensis Berliner resulting in 238 +/- 29 ng of Cry1Ac protein per milligram of total extractable protein in leaves. We tested 2 Hawaiian strains of diamondback moth: NO-QA was resistant to C ry1Ac and LAB-PS was susceptible. Larval and pupal durations, pupal weights , and adult emergence of the 2 strains were similar on nontransgenic canola , but differed significantly on transgenic canola. Transgenic canola killed all larvae tested from the susceptible strain. In contrast, for the resist ant strain, no differences occurred between transgenic and nontransgenic ca nola in larval survival and head capsule width at day 5, percentage pupatio n, pupal weight, percentage adult emergence, and extent of defoliation. For both the susceptible and resistant strains of diamondback moth, no differe nces were detected between transgenic and nontransgenic canola in feeding i nitiation or oviposition preference. The lack of discrimination between tra nsgenic and nontransgenic canola by neonates and ovipositing females indica tes that host choice behavior is independent from susceptibility to Cry1Ac. Development of resistant diamondback moth on transgenic canola without any adverse effects provides an example of a pest that has completely overcome high levels of a B. thuringiensis toxin expressed by a genetically enginee red plant.