Expression of cry genes from Bacillus thuringiensis: Influence on biochemical composition of transgenic cotton

Continuing need to increase agricultural production has spurred the urge for developing cultivars with high productivity and a high degree of resistance to insect pests. One of the factors constraining crop production is losses due to insect pests, estimated at 14% of the total agricultural production (US$ 250 billion), despite application of insecticides valued at $50 billion annually (Oerke 2006). However, many insect species, including cotton bollworm, Helicoverpa armigera (Hubner), have developed high levels of resistance to conventional insecticides. Therefore, there is a need to harness all the technologies, including biotechnology for crop protection for a sustainable growth in agriculture and food security. To achieve a satisfactory control of insect pests, genes encoding d-endotoxins from Bacillus thuringiensis (Bt) have been deployed in a number of crops including cotton, and approved for commercial cultivation in several countries. Because of the potential benefits of growing genetically modified crops, their cultivation has increased from 1.97 million ha in 1996 to over 160 million ha in 2011 (James 2011). Cotton cultivars with Bt genes for resistance to cotton bollworm, H. armigera have resulted in a significant decrease in number of insecticide sprays applied for bollworm control in cotton, and increased cottonseed yield (Sharma et al. 2004, Sharma and Pampapathy 2006, Dhillon et al. 2012). Although, the promise of genetically modified crops has been realized in several crops and in different regions for increasing crop production, it is important to address the concerns related to their impact on non-target organisms, biochemical composition and substantial equivalence to the conventional food