Risk assessment ofBacillus thuringiensisin wildBrassica rapa:A field simulation of introgressed transgenes

Abstract

Brassica crops are able to hybridize with closely related wild and weedy species such as Brassica rapa and therefore these species could become recipients of transgenes from GM brassica crops, such as oilseed rape. Transgenes which protect against herbivory, such as a gene conferring the production of a Bt toxin, could increase the recipient's fitness and therefore enhance its competitiveness. We used microbial Bt and several other pesticides to exclude several guilds of herbivores and thus simulate the effect of transgene introgression on the performance of wild B. rapa . There were only minor negative effects of excluding insect herbivores on the performance of B. rapa and it appears that vertebrate herbivory has a more significant effect. The advantages and disadvantages of simulating the risks associated with GM plants are discussed. If we apply this simulation to GM risk assessment and make inferences from these findings, the implications of this for gene flow from insect-resistant transgenic plants are that it will be of little significance should it occur.

The bucket and the searchlight: formulating and testing risk hypotheses about the weediness and invasiveness potential of transgenic crops

“…The outcome of this experiment is not inevitably higher seed output in the mock-inoculated group because the wild relative may be naturally immune to the pathogen, or may tolerate infection and show no reduction in seed production (Maule et al, 2007;Raybould and Cooper, 2005). In the case of introgression of insect resistance transgenes, the wild relative of the crop could be protected from insect attack with insecticides to simulate the effect of transgenic resistance (e.g., Raybould et al, 1999;Sutherland and Poppy, 2005). Another approach is to assume that the transgene leads to increased seed production and then test the hypothesis that increased seed production does not lead to increased abundance of the wild relative, in other words that the population growth rate is not seed-limited.…”