The Behavioral Response Of Nilaparvata Lugens To Induced Volatiles Of Rice Infected By RGSV

Volatile compounds emitted by plants, act as a communication cue to neighboring plants, insects and pathogens, play a very important role in the interactions between the plant, insect and pathogen. Previous studies have indicated that vector-borne pathogens can affect the frequency of the transmission of pathogens by change the phenotypes of their hosts and vectors, including the release of plant volatiles. In this reserch, we aimed to the interaction of rice, Nilaparvata lugens (BPH), and rice grassy stunt virus (RGSV) to understand whether pathogen-induced plant response may help transmission of the pathogen. We compared the change of plant volatiles of healthy and RGSV-infected rice plants, determined the behavioral response of Nilaparvata lugens to significantly different volatiles, and analysed the expression of the relevant genes involving in terpenoids biosynthetic pathway of RGSV-infected rice compare to that of healthy rice. The results were as follows:(1) Prepare the rough extracts from RGSV-infected and healthy rice, and then attract Nilaparvata lugens using the extracts. We found that Nilaparvata lugens were more attracted to extract from RGSV-infected rice than that from healthy rice. In addition, collect and analyse the volatiles from RGSV-infected and healthy rice by using dynamic headspace trapping analysis combined with GC-MS technique. Both seedling stage and tillering stage (the volatiles of tillering stage is higher quantitatively than that of seedling stage), RGSV induced an increase in total volatile emission from infected rice than healthy rice. Except for a, β-cedrene, other individual volatile increased; rather infected rice released the volatiles qualitatively similar to that of healthy rice, including mainly alcohols, aldehydes, esters, terpenes, alkanes and other compounds.(2) The behavioral responses of Nilaparvata lugens adults to eight rice volatile compounds under five different concentrations were studied with a Y-tube olfactometer. The results showed that acetophenone(1、10、100μg/μL), benzoic acid,methylester(0.1、1、10μg/μL) and cedrol (1、10μg/μL) had significantly attract effects on the adult brown planthopper. However, β-cedrene had significantly repellent effects only on the concentration of 0.1 μg/μL. Nonanal had no significantly attract or repellent effects to Nilaparvata lugens under the tested five concentration. Further compounds spraying experiment indicated rice had significantly attract effects on the adult brown planthopper after sparing than no-sprayed rice.(3) Expression analysis of the relevant genes involving in terpenoids biosynthetic pathway of RGSV-infected rice compare to that of healthy rice by using real-time PCR. The results showed that expression level of the relevant genes were up or down regulated in different stages. The symptom formation-related gene HMGR, SQS were down-regulated; however DXR was up-regulated; PHS was up-regulated in the first stage, then down-regulated in the next stages. STC was down-regulated firstly then up-regulated. MTC was significantly down-regulated. GPPS and DTC were down-regulated firstly then up-regulated.