Executive Summary : | Rice (Oryza sativa) is the staple food for more than half of the world`s population especially in South and South East Asian countries. The world rice crop is attacked by numerous insect pest causing major yield losses every year. Around the world, approximately 37% of rice production is lost annually due to insect pests (Dhaliwal 2015). Among these insects, the phloem sap feeders (plant- and leafhoppers of rice) are responsible for large scale devastation causing major yield losses. Since the early 1970s, rice varieties have been bred for resistance to plant- and leafhoppers especially Nilaparvata lugens (brown planthopper). Breeding for planthopper resistance has resulted in the identification of nearly 48 brown planthopper resistant gene loci/QTLs from wild and cultivated rice varieties and landraces. A few of these resistant gene loci (i.e. Bph1, bph2, Bph3, bph8 and Bph9) have been successfully introgressed into modern rice varieties, however insect biotypes/populations emerge that overcome these plant traits within a few years of varietal deployment. Recent studies state that the rate of planthopper adaptation to resistant rice varieties has been phenomenally rapid (Fujita et al 2013). Unfortunately the exact mechanism of planthopper adaptation to resistant rice is largely under studied. Herbivore salivary components have the ability to modify the innate defense mechanism of host plant aiding in better protection, nutrient access and adaptation. Studies on the salivary components of planthoppers and aphids provide evidence for their role in adaptation to host immunity genes. In the present study, we aim to investigate whether hopper adaption to resistant rice varieties is associated with salivary gland plasticity aiding in better feeding and survival rate on resistant rice by a series of planthopper selection experiment and salivary gland transcriptome and proteomics studies. By comparative analysis, the ubiquitous and specific salivary proteins and effector components facilitating adaptation will be unveiled. The present work will provide insights into the evolutional adaptation of insects to host plant by salivary approach, and would be useful in pest management. |