Population Genetic Structure Analysis And Wolbachia Detection Of Laodclphax Striafellus (Vector Of RSV)

The rice stripe disease is a kind of virus disease caused by Rice stripe virus (RSV), its prevalenceand outbreak closely linked to the small brown planthopper (SBPH, Laodelphax striatellus Fallén). TheSBPH is one of the most important agricultural pests, can transmit RSV and several other plantvirus, italso could cause economic losses directly by feeding on the crops. The SBPH have a wide rangedistribution and large amounts of host plants, the interactions among the insect, virus, symbionts andnature environments may bring a high genetic variation, which makes it difficult to manage the diseaseand pests. Thus, it is import to find out the population genetic structure of the SBPH populations hostingon rice, analyze its phylogeography and the symbionts in the SBPH. Then it provide clues to researchthe interaction mechanism between the virus and its vector, and the long-term effective pest control.In this study, we amplified two mitochondrial DNA (mtDNA) genes COI/Cyt b and the wsp geneof Wolbchia, combined with the SAM-SSR (Selectively Amplified Microsatellite) technology, analyzedthe SBPH populations and its symbiont (Wolbchia) from12localities in China by using a series ofbioinformatic methods like phylogenetic analysis, genetic variation parameters and so on. The principleachievements of this study are as follows:(1) We amplified two mitochondrial DNA (mtDNA) genes COI/Cyt b from12localities in11provinces, sequenced141individuals of these genes, almost covered all rice growing region in China.The sequences of COI gene have18haplotypes, the haplotype diversity (h) and nucleic diversity were0.74519and0.00304respectively. The Cyt b gene have26haplotypes, the haplotype diversity (h) andnucleic diversity were0.80963and0.00411respectively. The results of two N-J and UPGAM clusteranlysis and networks based on haplotypes show that the haplotypes of COI gene were clustered into twoclusters, the main haplotypes cluster I included from southwest of China (Sichuan) and the haplotypescluster II included from both southwest an non-southwest of China. The analysis of Cyt b gene alsohave the similar results, the haplotypes in cluster I main from southwest of China (Yunnan) and clusterII from both southwest and non-southwest of China. But, the AMOVA analysis of12populationsresults indicated that certain differences exsited in pairwise comparison of genetic distance byclassifying the12populations as one group, there were no significant variation.(2) Successfully developed12SSR markers from the SAM-SSR method, and use three of them toamplify160SBPH individuals from12localities. The UPGAM cluster anlysis showed that the sampleswere clustered into two clusters, cluster I included from southwest of China and cluster II included fromboth southwest an non-southwest, the similar results also gained from mtDNA genes.(3) We detected the Wolbahcia outer surface protein (wsp) gene in SBPH by the PCR method andsequences were analyzed by phylogenetic analysis, the average infection rate of Wolbachia in SBPHcollected from11regions in10provinces was96.41%. There was no geographical geneticdifferentiation for Walachia’s wsp gene. Wolbachia in SBPH and white-backed planthoppers (Sogatellafurcifera, WBPH) shared the same sequence homology of wsp gene, but differences (Similarity83.39%)were found in the brown planthopper (Nilaparvata lugens, BPH). The results gained in this study, SBPH and WBPH were infected by the same strain of Wolbachia, while BPH was by different strain.