Genetic diversity of cultivated and wild Ussurian Pear (Pyrus ussuriensis Maxim.) in China evaluated with M13-tailed SSR markers

Abstract

Eight genomic SSR markers with a M13 tail attached were used to assess the genetic diversity of 72 Ussurian Pear accessions (Pyrus ussuriensis Maxim.) in China. The M13-tailed method was effective in discriminating all the 32 wild accessions. All the 40 Ussurian Pear cultivars could be successfully discriminated with the exception of 4 sets of synonymies or spots. A total of 108 alleles were obtained with an average of 13.5 per locus. The expected heterozygosity, observed heterozygosity, and power of discrimination were 0.78, 0.63, and 0.86 respectively. Three triploid cultivars (‘Anli’, ‘Ruan’er’, and ‘Pitaiguo’), and one wild accession, P. ussuriensis ‘Xilin-3’, showed three alleles at some SSRs. The number of alleles and observed heterozygosity per locus for 40 Ussurian Pear cultivars were 9.1 and 0.62, respectively, lower than the values of 32 wild accessions which were 11.3 and 0.65, respectively. A dendrogram based on the SSR genotypes was obtained, showing two major groups corresponding to cultivated group and wild group. All the cultivars fell into the cultivated group. Some subgroups (Nanguoli subgroup, Zhibazi subgroup, Xiangshuili subgroup, Balixiang subgroup, Anli subgroup) could be found in the cultivated group. A very close relationship between ‘Huagaili’ and ‘Miansuan’, and a close relationship between ‘Anli’ and a wild accession, P. ussuriensis ‘Huangshanli’ could be found in Anli subgroup. ‘Nanguoli’ and ‘Xiaowuxiang’ showed a close relationship with at least one identical allele at each locus with the exception of NH015a.