Microsatellite Development And Genetic Diversity Of Euzophera Pyriella

Euzophera pyriella belongs to the order of Lepidoptera,class of Pyralidae,and family of Euzophera,which attacks several fruit trees including pear,apple,date,fig,apricot,padan apricot,peach,poplar etc.Its larve drills into the phloem of the tree body and eats fruits.Because the hazard of E.pyriella is hidden and difficult to prevent and control,the pest incidence increases year by year,causing great loss to the pear and date industries in Xinjiang.In this study,method of high-throughput transcriptome sequencing was used to develop microsatellite primers and analyze the genetic diversity of E.pyriella population in Xinjiang,which promoted the forming mechanism study on the disaster of E.pyriella.1.Development of microsatellite molecular markers of E.pyriellaIllumina（HiSeq2000）high-throughput sequencing platform was used to sequence the transcriptome of Euzophera pyriella.After sequence assembly,187,069non-redundant transcriptome sequences were obtained,with a data volume of 117.37Mbp and an average length of 627.42 bp.Among them,144,456 Unigenes sequences were 77.81 Mbp and an average length of 538.66 bp.There were 54,671 annotated Unigenes sequences in NR database,accounting for 37.85%.There were 43094annotations in GO database,accounting for 29.83%.In KEGG database,there were18460 comments,accounting for 12.78%.By SSR screening,the transcriptome data showed that 200 pairs of SSR labeled primers were synthesised randomly among14940 SSR sequences.122 pairs（61%）had amplification products,40 pairs amplified target fragments well,and 25 pairs of amplified primers had high polymorphism.2.Genetic diversity of E.pyriella populationBased on 8 microsatellite primers,genetic diversity analysis was carried out on15 geographic populations of E.pyriella.The average observed heterozygosity was0.2488,the average expected heterozygosity was 0.7512,and the average polymorphic information content（PIC）was 0.7162（>0.5）.These data indicated that the developed SSR markers were suitable for the study of population genetic diversity.The F_stt of the 8 microsatellite sites was 0.0152-0.3278（averaged 0.1530）.The F_stt was very close to 0.15,indicating that there was a medium and low genetic differentiation between the populations of E.pyriella.Among the 15 geographic populations,the number of alleles in the XH group were highest（6.3750）,and the number of alleles in the T24 group were lowest（4.0000）.The number of effective alleles were highest in the XH group（3.6594）,but lowest in the T24 group（2.7170）.The difference of average expected heterozygosity among 15 populations of E.pyriella was small.The average expected heterozygosity was 0.6012-0.6837,which was highest in the SY population.The average polymorphic information content（PIC）was 0.4725 for the ZY population and 0.4941 for the TM population,but the values of other geographic populations were all higher than 0.5.Except for the ZY population and TM population,all the remaining 13 populations had high genetic diversity.The UPGMA method was applied to the cluster analysis of 15 populations of E.pyriella.The 15populations of E.pyriella had no obvious branches.The T24,TK,XH,YC and TM populations were clustered into one group,the CL,MG and HM populations were clustered into one group,and the AS and ZY populations were clustered into one group.The AK,AW,SY,and KC populations were all clustered in the Aksu region as one group,but Alar populations appear on the next level.The regression analysis of the correlation between genetic distance and the corresponding geographic distance between 15 populations of E.pyriella showed that the correlation coefficient（R）was0.08367.In all,the genetic differentiation of E.pyriella is caused by other factors,and the contribution of geographic isolation is weak.