Study On Genetic Diversity Of Empoasca Vitis (Go|¨ The) Based On Mitochondrial Genes

Tea leafhopper [Empoasca vitis (G the)] belongs to Hemiptera, Cicadellidae, is the most dominantpest in tea gardens of China. Because of high occurrence quantity and large number of generations withheavy overlapping, Tea leafhoppers severely affect quality and quantity of tea products, which results ina huge economic loss. Leafhoppers are a highly diverse group and there are large amount of host plants,the diversification of leafhopper species using cladistic methods have been hindered by a paucity ofdiscrete, phylogenetically informative morphological characters. To understand tea leafhopper atspecies-level, the mitochondrial DNA16S rRNA and COI gene sequences of leafhoppers from12geological populations were analyzed to determine the genetic diversity and genetic differentiation,molecular phylogenetic tree was constructed to confirm the relationship between genetics and geology.The major research results are described as follows:1.Mitochondrial16S rRNA gene sequences of103individual leafhoppers from12differentgeographical populations were cloned and sequenced, including an outgroup species (Erythroneurasudra D.). We compared the homologous sequences of all the individuals, and then calculated nucleotidecomposition. The median-joining network was constructed by using Network4500. Through thesequential analysis, we found that the value of A+T was about76.8%and56nucleotide sites weresubstituted in the536bp fragment of leafhoppers.56haplotypes were detected in100individuals.Haplotype diversity index (H) and mean nucleotide diversity index (Pi) were0.971and0.006respectively. The gene flow (Nm) among12populations was1.64, and the overall Fst value was0.026.Molecular variance (AMOVA) analysis showed that a high proportion of the total genetic variance wasattributable to variations within populations (97.4%). The median-joining network of the56haplotypeswas not distinguish obviously into12-location groupings of haplotypes and was not correspond to eachgeographic population of leafhoppers.2.Mitochondrial DNA COI gene sequences of84individual leafhoppers from12differentgeographical populations and closely related species were cloned and sequenced. We compared thehomologous sequences and calculated nucleotide compositions of all the indibiduals. Molecularphylogenetic tree was constructed with the Neighbor-Joining and ML method. Based on sequentialanalyseis, we found that the value of A+T was about70.5%and112nucleotide sites were substituted inthe710bp fragment of leafhoppers, and62haplotypes were detected in84individuals. Haplotypediversity index (H) and mean nucleotide diversity index (Pi) were0.954and0.053respectively. Thegene flow (Nm) among the12populations was0.92, and The overall Fst value was0.100. Molecularvariance (AMOVA) analysis indicated that a high proportion of the total genetic variance wasattributable to variations with in populations (90.0%). The NJ and ML tree suggests that differentindividuals from12different geographical populations were located in different clusters and eachcluster are parallel. The genetic distance between tea leafhopper and peach leafhoop. is further thangrape leafhopper. The tree shows the genetic distance between tea leafhooper and Qingdao grapeleafhopper is nearest.3.ML tree suggests that Guizhou tea graden leafhopper contain two branches of clusters. But it isnot clear that Guizhou tea graden leafhoppers exist genetic differentiation or some species leafhopper.The results showed that there was no obvious genetic divergence among Empoasca vitis ofdifferent geographic populations.