Rsearch On The Phylogenetic Relationship Of 96 Tree Peony Cultivars

China has rich resources of peony cultivated varieties, and the genetic relationship between different cultivated groups is very complex. Xinan peony cultivated group is the precious local resource in southwest China, which has high value of garden exploitation and utilization. However there is no research on its genetic diversity and genetic relationship with other peony groups, so it is not clear about its cultivation origin till now. Based on the germplasm resources investigation and the collection of southwest peony cultivars, this study on the genetic relationship and genetic diversity of 96 peony cultivars, which consisted of 20 cultivars of Xinan, 50 cultivars of Zhongyuan, 18 cultivars of Xibei, 1 cultivars of Jiangnan and 1 wild peony Paeonia lutea, 3 cultivars from Japan, 2 from France, 1 from America, was carried out to use SCOT and SRAP molecular markers with morphological characteristics data by the total DNA extraction and PCR reaction system optimization. Finally it can not only provide the basis material for the future orientation breeding and new cultivars breeding and better for the development and utilization of germplasm, but also supplement the genetic background information of Xinan peony cultivars. The results of the study summarized as follows:(1) A modified 2×CTAB method was used to extract the genomic DNA from fresh leaves. The optimal SCOT-PCR reaction system contained 20 ng template DNA, 2.5mmol·L-1 Mg2+, 0.25mmol·L-1 dNTPs, 0.4μmol·L-1 primers and 0.6U Taq DNA polymerase in 10μL volume. Otherwise an optimal SRAP-PCR reaction mixture with 30 ng template DNA, 2.5mmol·L-1 Mg2+, 0.25mmol·L-1 dNTPs, 0.35μmol·L-1 primers and 0.7U Taq DNA polymerase.(2) 18 SCOT primers and 20 pairs of SRAP primer combination were selected to analyze DNA fragments polymorphism. 18 SCOT primers produced 182 bands, among which 172 bands were polymorphic and the polymorphic ratio reached to 94.50%. While a total of 868 bands were obtained by amplifying 96 peony samples from 20 primer pairs of SRAP, among which 854 bands were polymorphic and the polymorphic ratio attained to 98.89%.(3) The result showed that genetic similarity coefficients based on SCOT among all tested 96 samples ranged from 0.5523 to 0.8681, which hybrids 2 and hybrids 3 of P. rockii had the highest similarity coefficient, otherwise P. rockii with P. suffruticosa ‘Doulv’ and ‘Zhongdianzi 2’ had the lowest coefficient. The 96 samples were divided into eight branches at the genetic similarity coefficient of 0.6931.The first branch included 20 samples, which consisted of 15 Zhongyuan peony cultivars, 4 Xinan cultivars and 1 Jiangnan sample, the genetic similarity coefficient between ‘Lijiangfen 1’ and ‘Zhongdianfen’ had the closest phylogenetic relationship, moreover‘Lijiangzi 1’had much closer relationship with Zhongyuan cultivars. The second branch was composed of 2 Xinan samples of ‘Lijiangzi 3’ and ‘Zhaotongfen 1’. The third branch consisted of 35 traditional Zhongyuan samples, which ‘Wanghuasheng’ and ‘Shibahao’ had the highest similarity coefficient, but ‘Doulv’ had the far relationship with other cultivars. The fourth branch was made up of 18 cultivars, which included 3 Japanese samples, 1 French sample and 14 Xinan samples, meanwhile ‘Lijiangfen 2’ and ‘Lijiangfen 3’had the closest phylogenetic relationship and ‘Yanzhilou’ had a closer relationship with ‘Penzhouzi’ than with others in Tianpeng group, three Japanese cultivars clustered into a subbranch, but Franch sample ‘Jinge’ had the closer relationship with ‘Lijiangzi 2’ and ‘Shishanhuangguan’. The fifth branch included 17 hybrids of P. rockii. The sixth branch and the seventh branch involved only one wild species of P. rockii, P. lutea respectively. The eighth branch contained one American sample ‘Haihuang’ and one French cultivar ‘Jinhuang’.(4) The genetic similarity coefficients based on SRAP among all tested 96 cultivars varied from 0.5081 to 0.9173. The closest phylogenetic relationship existed between hybrids 2 and hybrids 3 of P. rockii. While the farthest phylogenetic relationship was between P. lutea and P. suffruticosa ‘Bangningzi’. 96 cultivars were divided into five branches at the genetic similarity coefficient of 0.6419.48 Zhongyuan cultivars formed the first branch, which the closest relationship was with ‘Gejinzi’ and ‘Weihua’, but the farthest relationship in ‘Yaohuang’ and ‘Doulv’ with others. The second branch involved in 27 samples including three subbranches, which 19 Xinan cultivars and Zhongyuan sample ‘Gaoganhong’ comprised of the first subbranch, the second subbranch contained three Japanese samples ‘Huawang’, ‘Daojing’, ‘Chuwu’ and one Xinan sample ‘Xiangyuban’, American cultivar ‘Haihuang’ and French samples ‘Jinhuang’ and ‘Jinge’ clustered into the third subbranch. P. rockii and its 17 hybrids, together with ‘Fendanbai’ clustered into the third branch. The fourth and fifth branch respectively contained one sample, ‘Lanxiuqiu’ and P. lutea.(5) Based on 30 morphology indexes of 50 Zhongyuan cultivars, the clustering results showed that both P. suffruticosa ‘Zhangyuanhong’ with ‘Wanghong’ and ‘Yaohuang’ with ‘Erqiao’ had the closest phylogenetic relationship, and revealed that the cultivars with the same pattern and colors had the closer phylogenetic relationship and that the cultivars with the similar colors or similar pattern also showed a close phylogenetic relationship.(6) According to results of two molecular markers and morphological clustering, it indicated four aspects as followed. Firstly, 96 peony samples was clustered by the geographical provenance, which the cultivars from the same geographical provenance showed a close phylogenetic relationship, moreover the samples with the same or similar colors also showed a close phylogenetic relationship. Secondly, among the different geographical provenance, the peony group from Xinan and Japan had the closer phylogenetic relationship, furthermore they had much more closer relationship with Zhongyuan group than with Xibei peony group. Thirdly, the cultivars with yellow colors had a complicated genetic background. The phylogenetic relationship of Zhongyuan peony with yellow and white colors was close. The wild species P. lutea showed a closer genetic relationship with French group ‘Jin Huang’ and American group ‘Haihuang’. This suggests that P. lutea be involved in the origins of P. suffruticosa ‘Haihuang’ and ‘Jin Huang’, but almost involved in origins of other peony cultivars.