Genetic Engineering for Insect Resistance

Abstract

Legume crops are the most important source of vegetable proteins in the diet of people in the developing world, especially the Indian subcontinent. These crops are also responsible for nitrogen enrichment of soil through symbiosis with nitrogen fixing bacteria. Legumes have been qualitatively and quantitatively improved by conventional breeding over the past five decades. However resistance to several pests and diseases still remains elusive which is the major limiting factor for productivity. Excessive use of synthetic, organic insecticides resulted in the degradation of environment, adverse effect on human health and development of resistant insects. Recent advances in genetic engineering have clearly demonstrated the possibility of incorporating foreign genes for desired characters while preserving the existing traits of improved genotypes. Reduction in the consumption of insecticides is only possible by introducing the genes encoding insecticidal proteins such as 8-endotoxins of Bacillus thuringiensis (Bt), protease inhibitors, alpha-amylase inhibitors, lectins, enzymes such as chitinase and peroxidase. Genetically modified legume crops carrying insect resistance genes have been shown to exhibit considerable protection against the target insects. It is possible to incorporate the resistance against more than one insect pest in the transgenic plants through genetic engineering. This can be achieved by introducing fusion genes or multiple genes in combination encoding the insecticidal proteins which are toxic against a wide range of target pests. Development of resistance in insects is a possibility which can be circumvented or prevented by deploying suitable resistance management strategies. Such approaches include the usage of multiple toxins, crop rotation practices, high or ultra dosage of toxins and refugia. Use of 8-endotoxins of Bacillus thuringiensis in conjunction with other bioinsecticides in an IPM mode can drastically reduce the consumption of chemical pesticides and pave the way for safe and sustainable agriculture.