Bt cotton (Gossypium sp.) in India and its agronomic requirements – A review

India has emerged as a major global partner in the production, processing and trade of raw cotton and its finished products. The genetically modified Bt cotton, containing the cry gene sourced from the soil bacterium Bacillus thuringiensis sub-species kurstaki, providing resistance against boll worms, represents a landmark in cotton research and development. The large-scale adoption of Bt cotton by Indian farmers in a span of 7 years is the power of this technology. Introduction of the Bt gene has altered the morphological, phenological and physiological characteristics of these introgressed cultivars. The development and commercialization of Bt cotton varieties like BN Bt and incorporation of herbicide tolerance are likely to further revolutonize the cotton production scenario. To harness the benefits of the Bt cotton and to sustain their yield potential, sound agro-techniques need to be standardized. This review provides an update on the agronomic research undertaken on Bt cotton especially under the diverse growing conditions in India and the effect of these agro-techniques on Cry toxin expression and fibre quality parameters.