Insect resistance in Rice (Oryza sativa L.): overview on current breeding interventions

Breeding for insect resistant varieties has been central to the integrated pest management as it offers an ecologically viable approach agianst biotic constraints. Considerable progress has been made in the past to incorporate resistance to insect pests of rice using conventional breeding approaches. However the diversity in insect pest population, continuous selection of virulent biotypes, lack of resistance sources in cultivated rice (Oryza sativa and O. glaberrima) gene pool, want of efficient insect rearing and varietal screening protocols and inherently complex genetics of resistance further necessitates supplementation of conventional breeding techniques with advanced molecular approaches. Hence, alternative approaches like wide hybridization to introgress resistance from other species of Oryza, transgenic approach to deploy Bt cry, snowdrop lectin and other plant derived genes are being actively pursued. The increasingly identified, mapped, cloned and characterized quantitative trait loci and genes related to insect resistance traits in rice have provided a solid foundation for direct selection and varietal improvement through molecular breeding. Utilization of DNA-based markers provided additional impetus to efficiency and precision of conventional plant breeding via marker-assisted selection to successfully introgress several genes for resistance to insect pests of rice. RNA interference technology has offered another reliable tool in meeting the challenges imposed by crop insects by targeting the enzymes/proteins integral to various biological processes of crop insects. This review briefly discusses the current progress and future prospects in molecular breeding for enhanced varietal tolerance to insect pests of rice.