Biotechnological interventions in host plant resistance

Abstract

Host plant resistance forms an integral part of integrated pest management. Conventional host plant resistance is slow and difficult to achieve due to the involvement of quantitative traits at several loci. However, recent biotechnological interventions have opened up new opportunities for pest control by providing an access to novel molecules, ability to change the level and pattern of expression of genes and development of transgenic varieties with insecticidal genes. Several transgenics have been developed in a number of crop plants including corn, rice, cotton, canola, soybean, tobacco, apple, potato and many others that have genes for δ-endotoxins from Bacillus thuriengiensis Berliner. The economic and environmental impact of adoption of such crops has been huge and it has led to a significant reduction in the global environmental impact of production agriculture. However, the reports on the development of insect resistance to the δ-endotoxins from Bt have raised questions on the sustainability of Bt-based pest management strategies. Gene-pyramiding, which comprises stacking of multiple genes and leads to simultaneous expression of more than one toxin in the transgenic variety, has been advocated as one of the solutions though it is also associated with problems such as development of cross- and multiple resistances. Further, possible environmental and ecological impacts, particularly gene-flow and effect on non-target organisms pose more serious questions and need to be addressed properly before the commercialization of a transgenic variety. This chapter focuses on the recent developments in insect-resistant transgenic varieties and their impact as well as the problems associated with them.