Investigation And Evaluation Of Wild Tree Peony(Paeonia Section Mouton DC.) Germplasm Resource In China

Tree peony,belonging to section Moutan DC.of the genus Paeonia L.（Paeoniaceae）,is a perennial woody shrub native to China,including nine wild species and one cultivar.As the important materials for the origin and evolution of cultivated tree peony,wild section Moutan species have important value of academic research and practical application.In recent years,with human disturbances and natural succession,the natural distributions of wild section Moutan species are quite different from those recorded by the predecessors.It was undertaken on the revision of geographical distribution of section Moutan species in China by the field investigation,herbarium specimens and literature record.Based on the field investigation,the phenotypic diversity and population dynamics of typical species were studied in order to provide the theoretical basis for the scientific protection of wild section Moutan species.Moreover,functional components of the seeds collected directly from the natural habitats of wild section Moutan species were evaluated,which would lay the foundation of further development and utilization of wild section Moutan species.The main results are shown as follows:1.Existing natural populations of nine species belonged to Section Mouton DC.distribute in 93 towns of 60 counties of 8 provinces in China.Four species,P.jishanensis,P.qiui,P.ostii,and P.rockii,are found in Shaanxi Province,while only P.jishanensis is found in Shanxi Province.P.rockii,found in Shaanxi,Gansu,Henan and Hubei Province,is the most widely distributed species,while P.potaninii is only found in Yajiang County,Sichuan Province.Subsection Vaginatae F.C.Stern is mainly distributed in the thickets and forest from 700 to 3000m in Ziwuling,Qinling-Daba Mountains and Eastern Tibetan Plateau,and Subsection Delavayanae F.C.Stern is mainly found in the limestone and thickets from 2000to 3600m in Northern Yunnan-Guizhou Plateau and Southern and Eastern Tibetan Plateau.From horizontal and vertical perspectives,the natural distribution areas of two subsections are different.2.Seven populations of P.rockii in Qinling and Ziwuling Mountain areas of Shaanxi Province were selected to analyze the phenotypic diversity based on 20 phenotypic traits from leaves,flowers and fruits by nested ANOVA,correlation analysis and cluster analysis.The results showed that there were highly significant differences in 20 phenotypic traits among populations.Plant height,Leaf length and seed diameter were highly significant differences within populations.The mean phenotypic differentiation coefficient of the 20 phenotypic traits was 71.07%,which indicated that the phenotypic variation mainly occurred among populations.The average variation coefficient of phenotype traits ranged from 7.04%in seed average weigh to 21.66%in seed number in a fruit,which showed that there was low variation of phenotypic traits in P.rockii populations.The average variation coefficient of traits on fruits was 14.45%,higher than that of leaves（13.19%）and flowers（11.40%）.Correlation analysis showed that reproductive growth was slightly affected by vegetative growth.The correlation analysis between geo-ecological factors and phenotypic traits showed that the latitude and longitude had significant effect on flower traits,and the average annual rainfall had the maximum influence on fruits.The cluster analysis on the phenotypic traits showed that 7 populations were divided into 3 groups associated with environmental factors,which were not strictly classified according to the geography distance.3.Numeric dynamics of P.qiui population were studied using the static life table,the survival curve,the fecundity schedule and the Leslie matrix model.It indicated that the P.qiui underwent environmental screening during its first 6 years and competitive self-thinning at the age between 9 to 15 years,the physiological life span of the species was about 12 years,and its maximum life span was about 27 years.The survival rate of P.qiui population exhibits as the Deevey-I type.The net reproductive rate（R₀=0.8005）,the intrinsic rate of increase（r_m=﹣0.0205）and the finite rate of increase（λ=0.9797）of P.qiui were relatively low,indicating that population of the species belongs to the type of decline.Results obtained by using the Leslie matrix model shows that total plant numbers of the species declined by 78.8%during the past 30 years.At present,the population is maintained mainly by suckers.Thus,the possible factors leading to the species being in an endangering state are biological characteristics,the population size,the habitat conditions and the disturbances from human activities.4.Four phenotypic characteristics of the seeds from 19 populations from nine wild tree peony species were examined,and five major fatty acids（FAs）in seed oils were quantitatively measured using gas chromatography-mass spectrometry.The results showed that the phenotypic seed characteristics,such as thousand seed weight（244.01-1772.91 g）,seed volume（91.31-1000.79 mm³）,weight rate of kernel and coat（1.29-3.62）and oil extraction ratio（20.32-34.69%）,dramatically varied.The unsaturated FAs contents were dominant,of whichα-linolenic（ALA）acid,linoleic acid,and oleic acid（OA）contents ranged from 14.84 to 42.54 g/100 g,7.33 to 19.66 g/100 g,and 15.07-35.31 g/100 g crude oil,respectively.These results suggested wild tree peony species could be selectively exploited for edible oil production.Based on the contents of the five FAs,the nine species were classified into two groups.The species belonging to subsection Vagiatae were arranged in cluster I and were characterized by high ALA content.Cluster II,consistent with subsection Delavayanae,had a high OA content.The FAs composition could be used as a chemotaxonomic marker for tree peony species.5.Phenolic content,antioxidant compounds and antioxidant activity of seeds from nine tree peony species were determined.Among the seed samples,P.rockii had the highest total flavonoid content,strongest DPPH and ABTS radical scavenging activities,and strongest cupric reducing capacity;P.decomposita subsp.rotundiloba had the highest total phenolic and flavanol contents,as well as the strongest hydroxyl radical scavenging activity.Sixteen individual phenolic compounds were quantitatively measured,with（+）-catechin being the most abundant component.Nine individual phenolic compounds previously unknown to be present in tree peony seeds were detected.The content of the phenolic compounds luteolin,paeonol,and the total flavonoid content were significantly correlated with four antioxidant activities.Hierarchical cluster analysis showed that P.rockii and P.decomposita subsp.rotundiloba could be clustered in a group having a high phenolic content and strong antioxidant activity.These results suggest P.rockii and P.decomposita subsp.rotundiloba are the most promising candidates as useful sources of natural antioxidants.