Control Effect Of Metarhizium Anisopliae And DsRNA On The Brown Planthopper

The brown planthopper(BPH)Nilaparvata lugens is an important migratory pest of rice.In order to develop new methods for controlling this pest,38 Metarhizium anisopliae strains transformed with BPH chitin synthase A dsRNA(dsNlCHSA)were screened,and the best strain was strain 23 based on their control effects against BPH.Aseptic culture and ITS sequence analysis confirmed that strain 23 could invade into the body of BPH.Using qPCR techniques,it was proved that dsNlCHSA transformed into the strain 23 played an interference role after infestion of BPH by M.anisopliae.The bioassay results showed that the half-lethal concentration of the 2nd instar nymph of BPH was 3.9*10^6 spores/ml of the strain 23.In the bioassay experiments on different stages of BPH,the strain 23 showed high lethal effects on young and old nymphs as well as adults of the BPH.In addition,the younger the developmental stage is,the faster the lethal rate;and the older the developmental stage is,the higher the lethal effect.In order to get more target genes for RNAi,we have also screened other dsRNA fragments that can be transferred to M.anisopliae.Kr-h1 is a downstream essential gene in the juvenile hormone signaling pathway,which regulates the growth and development of insects and promotes the formation of neuronal cells.In this study,thefull-length cDNA sequence of the BPH,Kr-h1,was obtained by gene cloning.Six dsRNAs were designed and screened according to the domain structure and database comparison.After synthesized the six dsRNAs and injected each of them into one day4 th instar larvae of BPH,all of the 6 dsRNAs resulted in lower expression of Kr-h1 in BPH.Among those dsRNAs that have homology only with Sogatella furcifera and Laodelphax striatellus,the control effect of K3 was the best.The mortality rate of BPH on the 15 th day reached 80.0%.This paper studied the biological control of thansgenic M.anisopliae mediated by dsRNA on N.lugens.These findings may provide novel clue for better control of the brown planthopper.