The Molecular Phylogeography Of Diaphorina Citri(Hemiptera:Psylloidea)Based On Mitochondrial Cytb And COI Gene Sequences

Diaphorina citri Kuwayama(Hemiptera: Psylloidea)is one of the most common pests impacting citrus orchards in southern China.It mainly damages to the plants of Rutaceae families,spreads Huanglongbing(HLB),and is the main natural vector of HLB.At present,D.citri has been a worldwide distribution,to the global citrus industry has brought a devastating disaster.In recent years,the distribution of D.citri in China has shifted to the north,which brings more challenges to pest control.For this study collected from nine provinces of China,48 populations of D.citri samples.Mitochondrial DNA Cytb genes and COI genes as molecular markers,the genetic diversity and genetic structure of D.citri populations in China were determined and has carried on the phylogenetic analysis,probes into the affect of forty-eight D.citri populations geographical factors of the structure,molecular systems for better prevention and treatment of D.citri provides some basic theory research.The main results of this study are as follows:(1)A total of 234 Cytb sequence fragments of D.citri were obtained,with the length of 786 bp and 229 COI sequence fragments,and the length of 706 bp.There was a significant bias of A+T percentage content in the base composition of the two molecular markers.(2)A total of 12 haplotypes were identified by Cytb molecular markers.Haplotype hap-1 is the most common haplotype.A total of 195 individual samples belong to hap-1 and are distributed in all provinces except Yunnan province.In addition,six private haplotypes were found,and the others shared haplotypes.A total of 15 haplotypes were identified with COI molecular markers.Haplotype hap-1 was also the most common haplotype,with a total of 178 samples.These 178 samples were also distributed in all provinces except Yunnan province,belonging to the most dominant haplotype.In addition,10 haplotypes were identified.(3)The worldwide D.citri sequences were downloaded from GenBank and analyzed with the sequences obtained in this study.Phylogenetic trees(ML tree and BI tree)indicate that there is a certain geographical structure of D.citri in China.D.citri populations in China mostly belongs to branch A,and only haplotype belonging to Yunnan xishuangbanna(XS)population belongs to branch B.The haplotype network based on the two markers also shows that D.citri with two branch lineages exists worldwide.The populations of D.citri in south,southeast and part of southwest China belong to the A lineages,while the B lineages only exist in xishuangbanna,Yunnan province.(4)Tajima's test and Fu's FS test were performed on the overall data of Cytb and COI markers,respectively.The results showed that the two genes were affected by purification selection.Changes in the natural habitat of D.citri greatly increase this selection pressure.Therefore,such selection may result in the loss of haplotypes and the expansion of rare haplotypes with advantages.