ABSTRACT
258Rice (Oryza sativa L.) is an important staple food crop providing a major source of nutritional calories for nearly one-third of world population. One of the major constraints in rice production is the damage caused by biotic stresses such as pest and disease. Among the insects, the major target pests of rice in Asia are the striped stem borer (SSB; Chilo suppressalis Walker), yellow stem borer (YSB; Scirpophaga incertulas Walker) (Lepidoptera; Pyralidae), and leaf folder (Marasmia spp. and Cnaphalocrocis medinalis). Insect pest management by chemicals has brought about considerable protection. Though plant breeders have been successful in developing insect resistant crop plants, their efforts are limited by the availability of insect resistance genes in germplasm and breakdown of resistance. The recent availability of the cloned resistance/defense genes provides additional tools for genetic engineering of improved cultivars by transformation. Among different transformation methods of rice, particle/microprojectile (biolistic) bombardment is now successfully used in many laboratories. The different insecticidal genes used for the control of insect pests include protease inhibitors, lectins, amylase inhibitors, and δ-endotoxins (Bt gene) produced by the soil bacterium, Bacillus thuringiensis. Among them, Bt gene offers a great scope for controlling insect pests.
