Genetically Modified (GM) Crops Harbouring Bacillus thuringiensis (BT) Gene(S) to Combat Biotic Stress Caused by Insect Pests

Abstract

Insect pests are a menace to the crop plants as they cause 15–22% annual crop loss. Bacillus thuringiensis (Bt) crystal protein toxin(s) have been observed to be effective against lepidopteran, coleopteran, dipteran and hemipteran insect pests. With the emergence of recombinant DNA technology, computational biology and plant transformation procedures, it is now possible to design, modify and transfer any gene (natural or synthetic) into crop plants especially, to cope with insect pests, herbicide tolerance, various abiotic stresses and to enhance the expression level and nutritional quality. Bt-based biopesticides are an alternative to synthetic pesticides and are insect- specific, effective, eco-friendly and cost-effective. Agrobacterium-mediated plant transformation technique utilizes the natural genetic engineering property of Agrobacterium tumefaciens which has played a pivotal role in plant genetic engineering and development of stable transgenics, over conventional breeding procedures. Several stable Bt-transgenics (potato, maize, cotton, soybean, canola, squash, rice, etc.) developed by various companies (Monsanto, Dow AgroSciences, Syngenta, Bayer cropScience, etc.) have been approved by Genetic Engineering Appraisal Committee (GEAC), Environment Protection Agency (EPA), and commercialized. The most successful story of Bt-transgenics is that of Bt-cotton (Bollgard: trade name) harbouring Bt-cry1Ac like gene. In order to avoid the development of insect resistance, various strategies such as use of hybrid gene, Bt-gene pyramiding, refugia strategies, enhanced expression of Bt-gene(s) and use of sterile insects are followed as and when required for maintaining the sustainability of Bt-technology. In the last few years, after analysing the effectiveness and promising future of this ‘green technology,’ there has been a remarkable progress in the list of countries accepting the Bt-GM crops.