Population Genetic Structure Of The Peach Fruit Moth Caposina Sasakii In Main Occurrance Regions Of China

The peach fruit moth,Carposina sasakii Matsumura(Lepidoptera: Carposinidae),is one of the most important orchard pests in China.So far,it remains to be confirmed whether there is genetic differentiation among host-associated populations of this pest.And it is not clear about the geographical population genetic structure of C.sasakii from main regions of China.Using the newly developed microsatellite loci and mitochondrial COI gene reported,we explored population genetic structure of this pest among host-associated and geographical populations.The main results were as follows:(1)Development of microsatellite markers of C.sasakiiIn total,4.70 GB raw data were generated by using the Illumina MiSeq highthroughtput sequencing system.After sequence assembly,about 479 Mb random sequences were obtained.Based on the random sequences of C.sasakii genome,95,153 micrsatellite loci were identified.Of them,dinucleotide is the most frequent motif(57.34%).A total of 64 loci were selected for initial evaluation of amplication efficiency and polymorphism.Thirty-five polymorphic markers were developed after assessing in 63 individuals of two geographical populations collected from Beijing and Hubei.Their allele numbers ranged from 2 to 9 with an average value of 4.60 per locus,while the polymorphism information content ranged from 0.075 to 0.696 with an average value of 0.407.Furthermore,the observed and expected heterozygosity varied from 0.000 to 0.677 and 0.062 to 0.771,respectively.Neutrality test showed that all of the loci were under neutral expectations.Two loci(CS31 and CS33)showed significant linkage disequilibrium across Beijing population(corrected by Holm's correction,p < 0.05),while 5 loci(CS05,CS17,CS21,CS29 and CS82)showed significant deviation form Hardy-Wenberg equilibrium in the both tested populations.(2)Analysis of population genetic structure and its influence factors of C.sasakiiNinteen 19 microsatellite loci and a segment of mitochondrial COI gene were used to assess the genetic diversity and genetic structure of C.sasakii among 363 individuals from seven plant hosts and nine regions.Both molecular markers clustered 7 hostassociated populations from Beijing into 1 group.BAPS and STRUCTURE or DAPC analysises indicated that there is no host-associated genetic differentiation occurred.Mantel test indicated that no significant association between genetic distance and geographical distance or environmental distance was observed among 7 host-associated populations.Based on microsatellite data,geographical populations were clustered into 3 groups(northern,southern and northeast groups).Most of individuals in 7 geographical populations(distributed in Shandong,Shanxi,Ningxia,Liaoning province and Beijing aeras)were dividied into the same cluster named northern cluster.The remaining clusters(southern and northeast)included HBYCM(Yichang of Hubei province)and HLHEP(Haerbin of Heilongjiang province)populations,respectively.Based on microsatellite loci data,strong genetic differentiation was found among geographical populations representing distinct geographical regions,and significant association between genetic distance and geographical distance or environmental distance.SPLITSTREE analysis revealed 4 lineages among 35 haplotypes in C.sasakii.The divergence time of the earliest haplotype was about 1.02 Ma.Approximate Bayesian Computation(ABC)analysis supported that C.sasakii possibly originated from the southern population and dispersed northward before the last glacial maximum during Quaternary.Our analyses showed that of geographical barriers and historical events strongly impact on the genetic structure of C.sasakii,however,the environmental factors and host plants should not be neglected.In this study,random sequences of C.sasakii genome were obtained.Microsatellite markers of C.sasakii were developed based on the sequenced random genome sequences.Population gentetic structure of this pest in main occurrence regions of China and its corresponding influence factors were unvovered.These results are not only important for the interpretation of host-associated genetic differentiation,geographical population structure and its influence factors of C.sasakii in China,but also provide scientific guidance for the development of management strategies for the control of this pest.