First-Generation Transgenic Cotton Crops

Cotton is an important natural fiber crop and is known as “white gold” due to its economic importance. Its seed is also a source of oil, proteins, and feed for the livestock. Sustaining cotton production has been a major challenge owing to the multitude of biotic and abiotic stresses. Among these, the infestation of insect pests and diseases are the most devastating yield depressing factors. Keeping insect population under control heavily relies on the application of chemicals (pesticides) which may raise serious environmental concerns. Production of insecticidal proteins in the cotton plants through different genetic means opened a new era of insect-pest management. On the basis of number of transgenes introduced, three different generations of the Bt-cotton (cotton expressing genes coding for different insect toxins from the soil bacterium Bacillus thuringiensis) have been developed. The first generation of Bt cotton carried a single Bt gene, while the second- and third-generation Bt cottons contained double and triple genes for a better control over lepidopteran insects. In addition to Bt genes, genes conferring tolerance to different herbicides have also been introduced in cotton for controling weeds more effectively. Cultivation of Bt cotton has been instrumental in controlling bollworms; however, the emergence of resistance in insects against the Bt toxins has been reported in few regions worldwide. In this chapter, current state of the art knowledge on transgenic cotton including generations of Bt cotton, mechanism of action, risk assessment, and prospects has been discussed.