Sustainable and Durable Insect Pest Resistance in Transgenic Crops

Insect pests constitute a major constraint in crop production. Approximately 15 % of agricultural production is lost every year to insects, and consequently farmers spend billions of US $ yearly to provide effective control using chemical insecticides. A number of major crops, for example, cotton, cannot be cultivated without heavy chemical inputs in the form of insecticides. Often such insecticides are highly toxic to non-target animals (and humans), they have serious negative environmental impacts, and increasing numbers of insect pests are capable of evolving resistance against chemical insecticides. Biological control has been pursued; however, results are, in most cases, marginal in row crop situations. We are thus faced with a problem in terms of being able to control damaging insect pests using conventional strategies. Recombinant DNA technology provides a complementary/alternative strategy to combat insect pests. Transgenic plants expressing Bt toxins have been used successfully to provide resistance against a number of insect pests for several years, with insect resistance being the second most widely used trait in transgenic crops (after herbicide resistance) in world agriculture. One potential problem with Bt-based insecticides is that they are very widely used, with up to 90 % of microbiological insect control products based on topically-applied Bt toxins. For this reason, there is concern that insects might evolve resistance to Bt toxins and indeed the diamondback moth (Plutella xylostella) has evolved resistance in some open field populations in response to repeated exposure to foliar sprays containing Bt proteins, while laboratory selection experiments with other insect pests have shown that recessive mutant alleles can confer resistance to multiple Bt toxins