| Development of resistance in insects
Challenges and competition between living organisms result in selection of mutants capable of facing such challenges and overcoming the competition. Bt toxins and genes of various kind being used in transgenics kill larvae of specific target species and may also have some leaky influence unless selected for high specificity. This precision to kill certain insects and lack of effect in animals and humans is based on the mechanism of action. Exposure to Bt in bacterial spray or transgenics can result in insect resistance in the long run. To delay the emergence of resistance, strategies like plantation of refuge non-transgenic crop along with transgenics or deployment of multiple form of Bt genes have been proposed. Nevertheless, use of Bt genes requires close surveillance and compliance about use of strategies helpful in suppression and delay of resistance development. Despite this, emergence of field resistance in insects against Bt has been observed. This has led to gene stacking in the next generation techniques. In the long run, this entails search for better strategies like use of insect-bite inducible promoter to drive the gene thereby minimizing the exposure, modification of cry genes, introduction of stacked genes, deployment of RNAi against insects or incorporation of Bt as part of IPM strategy.
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