This study examined 63 tree peony specimens, consisting of 3 wild species and 63 cultivars, using sequence-related amplified polymorphism (SRAP) markers for the purpose of detecting genomic polymorphisms. Bulk DNA samples from each specimen were evaluated with 23 SRAP primer pairs. Among the 296 different amplicons, 262 were polymorphic. The maximum parsimony, neighbor-joining, and unweighted pair-group method using arithmetic average trees were largely in congruence. In the three trees, the wild species Paeonia ludlowii and P. delavayi formed separate clusters with strong bootstrap support, and P. ostii was closely related to all cultivars. The cultivars were divided into groups with various corresponding bootstrap values. The genetic similarity among the genotypes ranged from 0.02 to 0.73. These results demonstrate that SRAP markers are effective in detecting genomic polymorphisms in the tree peony and should be useful for linkage map construction and molecular marker assisted selection breeding.

Petal flavonoid compositions of 39 tree peony cultivars from Xibei (northwest China) were investigated in order to study the chemotaxonomic relationship among tree peony species. Six anthocyanins, the 3- O-glucosides and 3,5-di- O-glucosides of three anthocyanidins-pelargonidin (Pg), cyanidin (Cy), and peonidin (Pn)-exist in petals without a blotch at the base. The flowers are classified into three anthocyanidin phenotypes: 'Pn, Pg>Cy'; 'Pn, Cy'; and 'Pn, Cy>Pg'. Furthermore, the yellow pigments are identified as three flavones and three flavonols: apigenin, luteolin, chrysoeriol, and kaempferol, quercetin, and isorhamnetin, respectively. Ward's minimum-variance cluster analysis with principal component analysis produced a dendrogram using standardized scores of 20 pigment variables. Of 39 cultivars, 11 clustered with white flowered Paeonia rockii and 17 with pink flowered P. rockii. The other 11 cultivars matched either P. delavayi or P. potaninii. The result suggests that the Xibei tree peony originated mainly from P. rockii.