Analyses Of The Geographic Population Diversity Of Asian Citrus Psyllid (Diaphorina Citri) In China Based On Complete Mitochondrial Genome

Asian citrus psyllid?ACP,Diaphorina citri Kuwayama?is the vector of huanglongbing?HLB?,which is the most devastating disease in citrus production worldwide.ACP transmits the Asian-form HLB?Candidatus Liberibacter asiaticus?and American-form HLB?Candidatus Liberibacter americanus?.It is the only vector of HLB in vast majority of citrus-growing regions in C hina,and is the most important pest in HLB present regions.?Candidatus Liberibacter spp.?areunculturable,and currently there is no cure method directly to the pathogen of HLB.It is managed mainly through the prevention of spread by ACP.ACP has been found in 13 provinces/regions in C hina.However,the epidemiology and population diversity are still unclear.It is widely believed that ACP has single source and spreads from southern to northern in C hina.In fact,ACP has a history of more than 100years in China and it is possible to havedifferent groups.In this study,we used complete mitochondrial genomes?mitogenomes?of ACP collected from 22 main citrus-growing regions for classifying the population.Specific primers were designed for population detection.The mitogenomes of different populations of ACP wereobtained and the specificity and regularity were analyzed.Methodology and findings are summarized:1.All 26 ACP mitogenomes,including 21 from C hina and 5 from south and south-east Asian countries were enclosed with genome size ranging from14,986 to 15,030 bp.There were no regularities of main CR length ranging from 893 to 936 bp among all mitogenomes.All ACP mitogenomes had the same gene order,gene direction and start/stop codons of each PC Gs as that of mt-GDpsy.2.Based on nucleotide diversity of the 13 PCGs and 2 rRN A genes among the 29mitogenomes of all available ACPs from 7 countries,including China,America,Pakistan,Indonesia,Cambodia,Vietnam and Malaysia in the world.Genes cox2,atp8,nad3,nad1and rrnL displayed the highest variability on average,cox2 and rrnL had the most variable region?window?.For the 22 samples collected from C hina,except for atp8,fourmost variable and variable regionsgeneswere the same as the former.Both cox1wereone of the most conservative PCGs.3.Phylogenetic tree built by 37 mitochondrial genes displayed the same structure as the one which built by the top five variable genes?cox2,atp8,nad3,nad1 and rrnL?.However,higher genetic distances were obtained in China among the subgroups when the tree was built by the top five variable genes.Two geographic ACP populations including five groups were found among the samples in C hina.4.Twenty of the 22 tRN A genes of all the ACP mitogenomes had standard cloverleaf structure.The trnSer^AGN could not form a stem-loop structure in the dihydrouridine arm,and there was no variable loop intrnTrp.Two ACP populations were also identified by the structure of trnAsn.The lengths of rrnL of ACP mitogenomes fromUSA and Pakistan were both 2 bp longer than other regions.5.Based on SNP comparison among 22 ACP mitogenomes fromC hina,11 genome types were showed by 17SNPs.Nad5hadfive SNPs,nad1 and rrnLboth had three,cobhadtwo,and cox2,trnAsp,nad3 and nad4all had one SNP.Thirteen of the 17 SNPs were in PCGs.Only three of them changed the amino acids,including one had conservative nonsynonymous substitution type located in 10908 bp and two locations charged amino acid substitution types,located in 7667 bp and 11726 bp respectively.