Search

Tree peony (Paeonia Sect. Moutan) is an economically important ornamental plant, but little is known about the genetic architecture of important ornamental traits. To effectively improve ornamental value, we require a better understanding of genetic architecture in the complex traits of the tree peony. Association mapping is a powerful tool for detection of variation associated with traits. Thus, we examined the genetic diversity and the population structure of 462 unrelated cultivated P. rockii individuals, then performed association mapping to identify simple sequence repeat (SSR) markers associated with 12 floral traits. We observed a moderate level of genetic diversity (PIC = 0.459) and low linkage disequilibrium (LD) between markers, demonstrating that the potential value of an LD approach in elucidating the molecular basis of the quantitative variation in this species. An analysis of population structure revealed three subgroups in the association population. Subsequent single-marker association analysis identified 46 significant associations, involving the 11 traits with 37 SSRs. These loci explained a small proportion of the phenotypic variance, ranging from 2.68 to 23.97% (mean 5.50%). We also validated 15 of the 46 associations in a linkage mapping population of 159 individuals. Finally, five associations were further confirmed in the linkage mapping population, involving the four traits with four SSRs. These results can serve as a foundation for further analyses of the genetic architecture of floral traits, and the SSRs associated in this work have potential applications in marker-assisted breeding in tree peony.

Paeonia jishanensis, one of the most important ancestral species of cultivated tree peonies, is an endangered ornamental and medicinal plant endemic to China. A total of 236 individuals of P. jishanensis from 10 extant populations were analysed using 21 EST-SSR markers to assess their genetic diversity and population structure. Moderate genetic diversity levels (HE = 0.340) and high genetic differentiation among populations (FST = 0.335) were revealed. Combining the results of STRUCTURE, PCoA and neighbour-joining analyses, the 10 populations were divided into four genetic groups that were significantly related to their geographical origins, which was further supported by hierarchical AMOVA showing the highest variation of 17.9% among groups. The Mantel test showed a significant positive correlation between genetic distance and geographic distance among populations (r = 0.873, P

Tree peony (Paeonia sect. Moutan) is a famous ornamental crop worldwide that is difficult to propagate. The present study provides efficient protocols for the micropropagation of three economically important tree peony cultivars (Paeonia suffruticosa ‘Jin Pao Hong’, P. suffruticosa ‘Wu Long Peng Sheng’, and P. × lemoinei ‘High Noon’). For optimal shoot multiplication, different concentrations of GA3 were added into woody plant medium (WPM) (double strength Ca2+) containing 1.0 mg l−1 BAP; 0.5 mg l−1 GA3 yielded the highest multiplication rate with more than 4 shoots per explant for the three cultivars. For better rooting, different polyamines (putrescine, spermine, or spermidine) were added individually to half-strength MS medium containing 1.0 mg l−1 IBA. 5.0, 1.0, and 1.0 mg l−1 putrescine produced the optimal rooting for ‘Jin Pao Hong’ (100%), ‘Wu Long Peng Sheng’ (100%), and ‘High Noon’ (80%), respectively; each rooted shoot had 4–6 roots measuring 4–6 cm in length. Poor survival rates during acclimatization were obtained for ‘Jin Pao Hong’ (52.6%), ‘Wu Long Peng Sheng’ (40.1%), and ‘High Noon’ (64.0%) when the plantlets were grown in uninoculated vermiculite/peat/perlite sterilized substrate; in contrast, ‘High Noon’ plantlets inoculated with Glomus mosseae showed a high survival rate (83.4%) and vigorous growth. The protocols reported in this study can be used for rapid and large-scale propagation of the three tree peony cultivars. Furthermore, this study raises interesting possibilities for stimulating the in vitro rooting of tree peony cultivars through polyamine application and for improving the ex vitro establishment of tree peony plantlets through arbuscular mycorrhizal fungi inoculation.

The list of authors and affiliations in the original article was incomplete. The correct information is shown here.

Arabidopsis thaliana Flowering locus T (FT) homologs have been shown to be sufficient to trigger flowering and to regulate flowering time in a wide range of plants. However, such a homologue for the perennial ornamental shrub tree peony has not yet been characterized. In this study, we isolated PsFT, which is a closely related FT homolog from reblooming [Paeonia ×lemoinei ‘High Noon’ (HN)] and nonreblooming [P. ×suffruticosa ‘Luo Yang Hong’ (LYH)] cultivars of tree peonies, and identified its potential role in the regulation of flowering time. The PsFT alleles from the two cultivars encode the same protein, which indicates that the polymorphisms observed in the coding region do not contribute to the distinct flowering phenotypes of HN and LYH. Comparative analyses of the PsFT expression patterns in HN and LYH indicated that PsFT might be associated with reblooming. Transgenic A. thaliana plants ectopically expressing PsFT exhibited a phenotype that included significantly early flowering compared with the wild-type (WT) plants. Taken together, our data provide valuable clues for shortening the juvenile periods and extending the flowering periods of perennial woody plants, such as tree peonies.

Paeonia ostii is a traditional ornamental and medicinal species that has attracted considerable interest for its high oil value. To facilitate the effective and rational cultivation and application of P. ostii in China, it is necessary to determine its potential spatial habitat distribution and environmental requirements. Using high-resolution environmental data for current and future climate scenarios, the potential suitable area and climatic requirements of P. ostii were modelled. Among the 11 environmental variables investigated, growing degree days, precipitation of the wettest month, mean temperature of the coldest quarter, global UV-B radiation, annual precipitation, and soil pH played major roles in determining the suitability of a habitat for the cultivation of P. ostii. Under the current environmental conditions in China, a total area of 20.31 × 105 km2 is suitable for growing P. ostii, accounting for 21.16% of the country’s total land area. Under the two future climate scenario/year combinations (i.e., representative concentration pathways [RCPs], RCP2.6 and RCP8.5 in 2050), this species would increase its suitable area at high latitudes while decrease at low latitudes. These results present valuable information and a theoretical reference point for identifying the suitable cultivation areas of P. ostii.

Tree peony is a well-known ornamental and medicinal plant in China, as well as a new crop that has been recently demonstrated to exhibit a great potential for edible oil production. However, only limited molecular markers are currently available in this species, which hinders its genetic and breeding studies. The objective of this study was to develop expressed sequence tag (EST)-simple sequence repeat (SSR) markers based on transcriptome sequences in tree peony. A total of 4,373 EST-SSRs were identified from 3,787 unigene sequences with an average of one SSR per 9.24 kb. Di-nucleotide repeats (46.26 %) were the most abundant type followed by tri-, hexa-, tetra-, and penta-nucleotide repeats. Moreover, 788 primer pairs were synthesised, out of which 373 primer pairs (47.3 %) produced successful amplifications, and 149 primer pairs (39.9 %) were polymorphic in both parents of one mapping population. The 30 polymorphic EST-SSR markers were randomly selected to assess polymorphism further in 36 tree peony accessions, in which the polymorphism information content values ranged from 0.36 to 0.85 with a mean of 0.69, thereby indicating a high level of informativeness. Transferability studies indicated that 95.3 % EST-SSR markers were transferable to nine other Paeonia species, thereby expanding their utility. In addition, as a demonstration of utility, a genetic relationship study was performed in 56 accessions. Cluster analysis using the neighbour-joining tree method demonstrated that major clusters corresponded to known pedigree trees. Thus, these newly developed markers will be valuable in facilitating marker-assisted selection breeding in tree peony and its related species.

The measurements of air temperature, relative humidity, and canopy structural characteristics were performed on calm sunny summer days in the Populus tomentosa community and the sun in the Beijing Olympic Forest Park, China. The aim of this study was to investigate in detail the correlations between the detailed cooling and humidifying effects and the canopy structural characteristics of the community. Hourly values of air temperature and relative humidity, canopy density, leaf area index and mean leaf angle were analysed statistically. The cooling effect reached its maximum by 13:00 h, whereas the humidifying effect reached its peak at 09:00 h. Compared with the control open space site, the community seemed to lower the air temperature by 1.0 °C–5.0 °C and to increase the relative humidity by 4%–15% during the daytime. Furthermore, the canopy density had a greater impact in terms of cooling and humidifying effects from 08:00 h to 13:00 h. In addition, these effects were more controlled by the canopy density and by the leaf area index than by the mean leaf angle from 15:00 h to 18:00 h. The results also suggest that the nature of the correlations will vary at different times of the day. Overall, these findings provide new insights into the relationships between canopy structural characteristics and diurnal variations in microclimatic parameters in urban forests, which could be studied in greater detail in future studies.

The tree peony belongs to section Moutan of Paeonia , known as the ‘King of Flowers’ in China and has great ornamental, medicinal and economic value. In this study, 12 novel polymorphic microsatellite markers from Paeonia ostii were developed and characterized by constructing a simple sequence repeat (SSR)-enriched genomic library. In total, 42 alleles across 48 tree peony accessions were detected, with an average of 3.5 alleles per locus, the number of effective alleles ranged from 1.4 to 4.7 with an average of 2.4 per locus, the observed and expected heterozygosity per locus ranged from 0.333 to 1.000 (an average of 0.785) and from 0.298 to 0.795 (an average of 0.541), respectively. The polymorphism information content (PIC) varied from 0.257 to 0.794, with an average of 0.468. Shannon Index was ranged from 0.594 to 1.771 and the mean value was 0.906. Moreover, these markers can also be amplified in herbaceous peonies Paeonia lactiflora and Paeonia veitchii of section Paeon . A neighbor-joining (NJ) tree was constructed using the proportion of shared alleles coefficient to assess the genetic relationships among species and cultivars. In the NJ tree, the accessions in the section Paeon spanned the extremes of the dendrogram and were used as an outgroup. The accessions in the section Moutan primarily grouped into two clusters. In cluster I, Paeonia rockii and Xibei Group cultivars clustered into one branch, indicating that P. rockii was the main ancestor of the Xibei cultivars. P. rockii and its cultivars were closely related to Paeonia decomposita . All Zhongyuan Group cultivars, Paeonia × lemoinei hybrids and P. ostii formed clusterII. P. ostii grouped with Zhongyuan cultivars, indicating that P. ostii contributed significant genetic information to Zhongyuan cultivars. Zhongyuan cultivars and P. × lemoinei hybrids were divided into groups with various corresponding bootstrap values. Principal component analysis (PCA) based on gene frequency further illustrated these genetic relationships. PCA supported the results of the clustering analysis, and it is easily discernable that cultivars from the same group distributed together, while wild accessions with a close relationship to cultivars were distributed with the cultivars. The results show that these SSR markers are very powerful in studying genetic relationships and that they have the ability to cross-amplify in other Paeoniaceae family members. Furthermore, the new SSR markers will be useful tools in assessing genetic diversity, detecting quantitative trait loci (QTL) and finally in facilitating marker-assisted selection (MAS).

An understanding of plant domestication history provides insights into general mechanisms of plant adaptation and diversification and can guide breeding programmes that aim to improve cultivated species. Cultivated tree peonies (genus Paeonia L.) are among the most popular ornamental plants in the world; yet, the history of their domestication is still unresolved. Here, we explored whether the domestication in China of historically cultivated peonies, that is, the common and flare cultivated tree peonies, was a single event or whether independent domestications occurred. We used 14 nuclear microsatellite markers and a comprehensive set of 553 tree peonies collected across China, including common tree peonies, flare tree peonies and the wild species or subspecies that are potential contributors to the cultivated tree peonies, that is, Paeonia rockii ssp. rockii, P. rockii ssp. atava, P. jishanensis and P. decomposita. Assignment methods, a principal component analysis and approximate Bayesian computations provided clear evidence for independent domestications of these common tree and flare tree peonies from two distinct and allopatric wild species, P. jishanensis and P. rockii ssp. atava, respectively. This study provides the first example of independent domestications of cultivated trees from distinct species and locations. This work also yields crucial insight into the history of domestication of one of the most popular woody ornamental plants. The cultivated peonies represent an interesting case of parallel and convergent evolution. The information obtained in this study will be valuable both for improving current tree peony breeding strategies and for understanding the mechanisms of domestication, diversification and adaptation in plants.

Herbaceous peony (Paeonia lactiflora) is a globally important ornamental plant. Spontaneous floral mutations occur frequently during cultivation, and are selected as a way to release new cultivars, but the underlying evolutionary developmental genetics remain largely elusive. Here, we investigated a collection of spontaneous corolla mutational plants (SCMPs) whose other floral organs were virtually unaffected. Unlike the corolla in normal plants (NPs) that withered soon after fertilization, the transformed corolla (petals) in SCMPs was greenish and persistent similar to the calyx (sepals). Epidermal cellular morphology of the SCMP corolla was also similar to that of calyx cells, further suggesting a sepaloid corolla in SCMPs. Ten floral MADS-box genes from these Paeonia plants were comparatively characterized with respect to sequence and expression. Codogenic sequence variation of these MADS-box genes was not linked to corolla changes in SCMPs. However, we found that both APETALA3 (AP3) and PISTILLATA (PI) lineages of B-class MADS-box genes were duplicated, and subsequent selective expression alterations of these genes were closely associated with the origin of SCMPs. AP3-PI obligate heterodimerization, essential for organ identity of corolla and stamens, was robustly detected. However, selective down-regulation of these duplicated genes might result in a reduction of this obligate heterodimer concentration in a corolla-specific manner, leading to the sepaloid corolla in SCMPs, thus representing a new sepaloid corolla model taking advantage of gene duplication. Our work suggests that modifying floral MADS-box genes could facilitate the breeding of novel cultivars with distinct floral morphology in ornamental plants, and also provides new insights into the functional evolution of the MADS-box genes in plants.

The endangered species Paeonia rockii is the most important ancestral species of the cultivated tree peonies. These well-known ornamental plants are termed the ‘King of Flowers’ in China. In this study, we investigated the genetic diversity and phylogeographic structure of 335 wild samples from 20 populations throughout the entire distributional range of the species based on three chloroplast DNA sequences (petB–petD, rps16–trnQ and psbA–trnH). At those loci, high levels of genetic differentiation (G ST = 0.94) and low levels of genetic variation (θ = 0.00185) were detected. The intraspecific phylogeny revealed four groups, the western group, the Taibai mountain group, the northern group and the eastern group, which closely coincided with the geographic distribution of the species. A phylogeographic structure of this kind could result from a number of integrated factors, such as allopatric fragmentation, climatic fluctuations, increased abortion and declining germination of seeds, or lack of gene flow among populations, especially across the geographic barrier of the high Qinling Mountains, and it could also result from adaptive evolution. For conservation purposes, each extant population of P. rockii should be recognized as a conservation-significant unit, and a more stringent conservation strategy should incorporate in situ and ex situ methods.

In Paeonia, hybridization is an important path for both the development of new cultivars and species formation in nature, but the characterization of hybrids has long been a problem. To establish the relationship among Paeonia yananensis, P. jishanensis, and P. rockii, we sampled 159 individuals from 11 populations around the core population of P. yananensis. Samples were subjected to morphological analysis of 22 characters and molecular analysis of three chloroplast DNA (cpDNA) fragments and 14 microsatellites. Paeonia yananensis was distinguishable from the other two species on the basis of morphological characteristics. The phylogenetic tree based on three intergenic spacers in the chloroplast genome (petB‐petD, rps16‐trnQ, and psbA‐trnH) demonstrated that P. yananensis was very closely related to P. jishanensis. However, analysis of 14 microsatellite loci revealed that P. yananensis shared a considerable number of alleles with both P. jishanensis and P. rockii. These results demonstrated that P. yanan...

To investigate the diurnal variation of the correlations between the cooling and humidifying effects and canopy structural characteristics of the Koelreuteria paniculata community, the measurements of air temperature, relative humidity, canopy density, leaf area index (LAI) and mean leaf angle (MLA) were performed on calm sunny summer days in the community in Beijing Olympic Forest Park, China. There were significant correlations between the canopy density, LAI and MLA, which affected the cooling and humidifying effects together. The cooling effect reached its maximum by 12:00, whereas the humidifying effect reached its peak at 10:00. Compared with the control open space site, the community appeared to lower the air temperature by 0.43 to 7.53 °C and to increase the relative humidity by 1%-22% during the daytime. However, the cooling and humidifying effects seem to be not effective during the night. The canopy density and LAI were better for determining the cooling and humidifying effects from 9:00 to 12:00. However, these effects were largely controlled only by the canopy density from 12:00 to 14:00 and were significantly correlated with the canopy density and LAI afterwards until 18:00.

 Premise of the study : Microsatellite (simple sequence repeat, SSR) primers were developed for the Chinese peony, P. lactifl ora , to investigate the diversity within Chinese peony germplasm resources.  Methods and Results : Using an SSR-enriched genomic library, a set of 10 unique polymorphic genomic SSRs was developed and characterized. The primers amplifi ed 61 alleles in all 10 loci, including di-, tri-, and tetranucleotide repeats. The primers were also effective for P. veitchii and P. obovata .  Conclusions : The new primers will be useful for genetic research of the Chinese peony and extend the repertoire of SSR markers available to study the herbaceous taxa in Paeonia .

Morphological development of forced tree peony (Paeonia suffruticosa) was observed in 17 Chinese and 3 Japanese cultivars (cvs) and the effects of pre-chilling on the growth and development in the Chinese and Japanese cv groups were compared. The development from bud swelling to flowering was divided into 8 stages. The leaves, stem and flower buds mainly grew during stages IV-VII, and stage VI was the longest showing the most vigorous growth. Stages III, IV and V were very complicated in morphology and varied with the cv, but could be identified easily by the leaf development. The pre-chilling promoted the growth and advanced the flowering, but the stage sensitive to the chilling in the Chinese cvs differed from that in Japanese cvs, which indicated the existence of different growth mechanisms. The pre-chilling was effective at the early stages in the Chinese cvs, but at the later stages in the Japanese cvs. The Chinese cvs grew more rapidly and responded to low temperature at an earlier stage, but their cut flower quality was inferior to the Japanese cvs. These results corresponded to a smaller requirement of cumulative temperature for flowering in the Chinese cvs. The pre-chilling decreased the stem length and foliage extension, but promoted the flower size and advanced the flowering date. Non-flowering cvs had normal leaves developed a normal stem and responded to pre-chilling as well as did the flowering cv. These results suggested that the vegetative growth is somewhat independent of the generative growth.

Background Tree peonies are great ornamental plants associated with a rich ethnobotanical history in Chinese culture and have recently been used as an evolutionary model. The Qinling Mountains represent a significant geographic barrier in Asia, dividing mainland China into northern (temperate) and southern (semi–tropical) regions; however, their flora has not been well analyzed. In this study, the genetic differentiation and genetic structure of Paeonia rockii and the role of the Qinling Mountains as a barrier that has driven intraspecific fragmentation were evaluated using 14 microsatellite markers. Methodology/Principal Findings Twenty wild populations were sampled from the distributional range of P. rockii. Significant population differentiation was suggested (FST value of 0.302). Moderate genetic diversity at the population level (HS of 0.516) and high population diversity at the species level (HT of 0.749) were detected. Significant excess homozygosity (FIS of 0.076) and recent population bottlenecks were detected in three populations. Bayesian clusters, population genetic trees and principal coordinate analysis all classified the P. rockii populations into three genetic groups and one admixed Wenxian population. An isolation-by-distance model for P. rockii was suggested by Mantel tests (r = 0.6074, P