Molecular Identification Establishment And Genetic Relationship Analysis Of Pear Accessions In Northern China Using The Fluorescent-labeled SSR Markers

China is one of the center of origin and the main diversity center of Pyrus and pears were considered to be originated in the southwestern mountain area of China in the third century.Pears had been cultivated for more than 3000 years in China,which cultivated and production were the third in the main fruits of China.According to its original distribution area,Pyrus could be divided geographically into two groups: the occidental pear group and the oriental pear group.China is one of the important oriental pear origin with rich germplasm resources,and there were 130 Pyrus species had been named.Faced with so many new germplasms,classification,phylogenetic relationship and population structure of germplasms of Pyrus were of great significance not only for pear germplasm breeding,but also for protecting intellectual property of these varieties.SSR markers are suitable for the research,since they are quantity,highly polymorph,codominant,specificity,high frequency,repeatability and easily manipulation.A total of 294 pear accessions were analyzed by SSR markers in this study for the construction molecular identity card,phylogenetic relationship analysis and population structure analysis,including one hundred and thirty-seven P.bretschneideri accessions,fifty-seven P.ussuriensis accessions,twenty-five P.pyrifolia accessions,nineteen P.sinkiangensis accession,forty-three hybrid accessions,one P.pashia,three P.betuleafolia,one P.hopeiensis,two P.phaeocarpa,four P.xerophila,two P.communis.The main results of this experiment are as follows:1.17 pairs of fluorescent labeled SSR primers on 294 Pyrus germplasms were amplified 400 alleles,per loci had allele numbers ranged from 15 to 35,with the average number 23.5.The fragment length was ranged from 63 bp to 364 bp.The expected heterozygosity was ranged from 0.710 to 0.904,the observed heterozygosity was ranged from 0.418 to 0.833,the Shannon’s information index was ranged from 1.697 to 2.707.The primers could distinguish the number of germplasms in this research ranged from 42 to 103,with the average 72.The identified rate was ranged from 14.3% to 35.0%,with the average 25.6%.2.Molecular identification and bar code identification of 294 pear germplasms were constructed.294 accessions of pears can be divided into 4 classes by cluster analysis.The result indicated a geographical correlation within the 4 classes.Besides ‘Suizhong xiehuatian’ and ‘Fenhongxiao’,other varieties could be separated,which include the sport mutation accessions ‘Nanguoli’,‘Nanguosihao’ and ‘Dananguo’,‘Jianba’ and ‘Jianbawang’,‘Qiuzi’ and ‘Tianqiuzi’.The sport mutation accessions of pear can be distinguished by SSR markers.Generally,SSR markers can be used as a useful method for pear identification and protection.3.The genetic relationship of pear germplasm in west China was close.The genetic relationship of pear germplasm indicated a geographical correlation.The genetic background of P.bretschneideri is significantly different from other groups,which divided into two types that was the North China Plain white pear and near the Yanshan mountain range white pear.The genetic relationship of Pyrus sinkiangensis and the pears in western region were close.The genetic background of the wild P.ussuriensis accessions and the cultivars P.ussuriensis accessions were distinct distinction and their relationships were far.4.The ‘Korla pear’ was Pyrus sinkiangensis Yü with the complex genetic backgrounds of the white pear near the Yanshan mountain range,the wild P.ussuriensis accessions and the cultivars P.ussuriensis accessions.‘Tiepi’,‘Hongmi’ and ‘Feixian hongli’ should be classified as white pear.The bretschneideri also had brown peel varieties.The ‘Pingguoli’ pear might be introgression from Pyrus bretschneideri and Pyrus ussuriensis.‘Yeli1’ and ‘Yeli2’ should be classified as white pear.