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• The new LC-MS/MS strategy detects polyphenol metabolites in edible flowers. • The pseudo-targeted screening method enables accuracy and quantification. • Using the new strategy, 43 polyphenol metabolites were detected in 27 edible flowers. • Significant variations in polyphenol types and levels among the 27 flowers. • Enriched research on polyphenols in edible flowers;model applicable to other species. Edible flowers, as a food ingredient, are rich in bioactive substance and have received a lot of attention. In this study, we have established a pseudo-targeting method based on Multi Reaction Monitoring (MRM) - Enhanced Product Ions (EPI) in the Information Dependent Acquisition (IDA) mode. The results showed that a total of 43 metabolites, including flavonoids, phenolic acids, and terpenes were detected in 27 edible flowers using integrated liquid chromatography-tandem mass spectrometry (LC-MS/MS) strategy. Rutin was measured in all edible flowers, but the levels varied significantly among the different varieties of flowers, with the highest being about 3500 times the lowest. Albiflorin and paeoniflorin are polyphenolic substance unique to Paeonia suffruticosa. The cyanidin 3-O-glucoside chloride content in reddish-purple flowers is higher than that of other colors. Dicoumarin and 4-hydroxycoumarin were discovered in edible flowers for the first time. This study established a pseudo-targeted detection method to reveal the distribution of polyphenolic metabolites and enriched the research on polyphenolic metabolites in edible flowers. It can also serve as a general strategy to detect metabolites in other agricultural products, providing valuable information about potential metabolites for consumers. [ABSTRACT FROM AUTHOR]

• The tree peony cultivar 'High Noon' contains 49 compounds of floral volatiles. • The linalool content is significantly higher than other floral volatiles. • The PsuLIS gene was successfully cloned from the tree peony cultivar 'High Noon'. • The expression of the PsuLIS gene was consistent with that of linalool emission. • The PsuLIS regulates linalool synthesis through in vivo and in vitro experiments. The floral volatiles, many of which have fragrances, are one of the important quality characteristics of ornamental plants. Tree peony (Paeonia suffruticosa) is a famous traditional Chinese flower that is well-known in many countries around the world. However, the composition and formation mechanism of volatiles in tree peony flowers is unclear. Here, we analyzed the pattern of floral volatiles emitted and further cloned and analyzed the function of the PsuLIS (linalool synthetase) gene in cultivated tree peony cultivar 'High Noon' cultivated in the field. 49 compounds of floral volatiles were detected by using GC–MS in cultivated tree peony cultivar 'High Noon', with linalool having the highest content among all substances, which is much higher than that of other substances. Their relative content was separately highest at full blooming during the flowering process and at petals in various floral organ. The diurnal change of floral volatiles is highest during 10:00–12:00 and lowest during 16:00–18:00. Furthermore, the PsuLIS gene was cloned with an open reading frame of 1698 bp and encodes 565 amino acids. The phylogenetic analysis showed that the protein of PsuLIS has the closest evolutionary relationship with LIS in Actinidia arguta. The expression pattern of the PsuLIS gene, which exhibits its highest expression during the full blooming stage, in petals and from 10:00–12:00, demonstrated consistency with the emission pattern of linalool and displayed a significant positive correlation. Additionally, tree peony cultivar 'High Noon' plants were obtained through knockdown using the virus-induced gene silencing (VIGS) system. The relative expression of the PsuLIS gene in transient overexpression plants and knockdown plants were separately increasing by 3.8 times and decreasing by 74.7% compared to wild type plants, and the expression pattern of the PsuLIS gene was consistent with the variation trend observed in linalool content across different genotype cultivated tree peony cultivar 'High Noon' plants. The recombinant PsuLIS protein can convert geranyl diphosphate (GPP) to linalool in vitro. The aforementioned findings indicate that the PsuLIS gene plays a crucial role in regulating linalool synthesis in cultivated tree peony cultivar 'High Noon', and laying the foundation for cultivating different fragrance types of peonies. [ABSTRACT FROM AUTHOR]

• ClO 2 increased the flower diameter and extended the vase life of tree peony. • ClO 2 treatment slowed sugar starvation and protein degradation in cut flowers. • ClO 2 treatment increased antioxidant enzyme activity in cut flowers. • ClO 2 treatment prevented bacterial growth to prevent xylem clogging in cut flowers. • ClO 2 reduced ethylene release and regulated ethylene-related gene expression. Chlorine dioxide (ClO 2) is an effective fungicide that can be used to mitigate post-harvest mechanical damage and bacterial contamination that can negatively affect the quality and longevity of fresh-cut flowers. To further explore the role of ClO 2 in the preservation of peony cut flowers, we set different concentrations of ClO 2 (0, 0.025, 0.050, 0.075, and 0.100 g·L−1), and we found that the 0.100 g·L−1 ClO 2 treatment extended the vase for 3.2 days longer than CK. The ClO 2 treatment increased water uptake of cut flowers by 37.5 % compared to CK, thus maintaining a higher fresh weight. It also retarded the reduction of soluble sugars and proteins. In addition, ClO 2 treatment increased the activities of antioxidant enzymes such as superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) by 30.9 %, 31.5 %, and 10.0 % each, respectively, and decreased the levels of malondialdehyde and hydrogen peroxide, respectively, when compared with CK. To further investigate its mechanism of action, the morphological characteristics of the stem bases of treated and untreated peony cut flowers were analyzed by using a bacterial inhibition assay and scanning electron microscopy (SEM), and ClO 2 not only inhibited the growth of stem-end bacteria but also reduced the lignin content and the activities of related enzymes. In addition, ethylene production decreased after 0.100 g·L−1 ClO 2 treatment, which might be related to the down-regulation of the ethylene synthase gene PsACO1. The expression of ethylene signaling genes PsETR1, PsEIL3 , and PsERF1 was also affected. Therefore, the ClO 2 treatment might be used as a bactericide to enhance the vase life of P. suffruticosa 'Luoyang Hong' cut flowers. [ABSTRACT FROM AUTHOR]

• Multi-omics (transcriptomics, proteomics, and metabolomics) were used to analyses the mechanism of flower color formation in bicolor P. suffruticosa 'Erqiao'. • The 6 bp insertion mutation of PsF3′H existed only in 'Erqiao' and was stably expressed in the pink-white petals, not other P. suffruticosa cultivars or 'Erqiao' tissues. • The insertion mutation of PsF3′H gene which only stably expressed in pink-white petals reduced the synthesis of the PsF3′H protein and led to the obstruction of anthocyanin synthesis, which further changed the synthesis direction of the entire metabolic pathway. The bicolor phenotype is conducive to revealing the changes in plant flower color and an important scientific model for studying the regulatory mechanism of flower color. The flowers of Paeonia suffruticosa 'Erqiao' have two colors, pink-white and purple-red, and bicolor flowers are rare, possessing unique ornamental value. The distribution of the two colors in a bicolor 'Erqiao' flower is similar to a pie chart and can be divided into two distinct parts, with the percentages of the two parts varying. We analyzed the mechanism of flower color formation in 'Erqiao' using transcriptomics, proteomics, and metabolomics. The results showed that the differentially abundant metabolites (DAMs), differentially abundant proteins (DAPs), and differentially expressed genes (DEGs) in the two petal types were primarily enriched in phenylpropanoid and flavonoid biosynthesis. Compared with purple-red petals, the PsF3′H protein content in pink-white petals was lower than that in purple-red petals. The content of PsF3′H 's downstream metabolites decreased, while that of some metabolites in the collateral branch of phenylpropanoid biosynthesis increased. The PsF3′H sequence analysis of different P. suffruticosa cultivars and 'Erqiao' tissues revealed that the 6 bp insertion mutation of PsF3′H existed only in 'Erqiao' and was stably expressed in the pink-white petals. Using virus-induced gene silencing to silence PsF3′H in 'Erqiao' petals, the color of the petals faded significantly. Therefore, through multi-omics analysis, we found that the insertion mutation of PsF3′H reduced the synthesis of the PsF3′H protein and led to the obstruction of anthocyanin synthesis; furthermore, other branches and metabolic pathways of the upstream pathway were more active, thus changing the synthesis direction of the entire metabolic pathway. The 6-bp insertion mutation of PsF3′H may be a reason for the rare appearance of bicolor flowers and the unstable ratio of two-colored petals in 'Erqiao'. This study provides new insights into the formation of the bicolor flower phenotype in 'Erqiao'. [ABSTRACT FROM AUTHOR]

• Triploidization of the first found allotriploid tree peony, P. × lemoinei 'Oukan' (2 n =3 x =15, AAB), were contributed by 2 n gametes produced by its seed parent, P. × lemoinei 'High Noon' (2 n =2 x =10, AB). • Weak 45S rDNA signals were newly detected at terminal region in the short arm of certain chromosome 1 in A-genome (P. suffruticosa), and at interstitial-distal region in the long arm of chromosome 5 in both A- and B-genome (P. delavayi). • The dual in series sites of 5S rDNA, colocalized with a 45S rDNA site, located on the short arm of chromosome 3 in both A- and B-genome. Polyploid breeding is one of the most important approaches to improve the traits of cultivated plants, but there has been no feasible method to get polyploid tree peony. In this study, we revealed a sexual triploidization approach from a diploid intersubsectional hybrid tree peony, Paeonia × lemoinei 'High Noon', to an allotriploid one, P. × lemoinei 'Oukan', by accurate karyotyping based on genomic in situ hybridization (GISH) and fluorescence in situ hybridization (FISH). The ancestor genomes from P. suffruticosa and P. delavayi , which were defined as A-genome and B-genome respectively, were clearly distinguished by GISH in 'High Noon' and 'Oukan'. Nonhomologous chromosomes were successfully recognized by means of 5S and 45S rDNA FISH. Karyotype comparation based on GISH and FISH indicated that the B-genome and one of the two A-genomes in 'Oukan' (2 n =3 x =15, AAB) were highly consistent to the corresponding genomes in 'High Noon' (2 n =2 x =10, AB), implying the triploid origination via 2 n gametes produced by first division restitution (FDR). In addition, it was demonstrated for the first time that the dual in series sites of 5S rDNA located on the short arm of chromosome 3 in both A and B-genomes. Besides the familiar strong 45S rDNA signals observed at terminal region of short arms, single weak 45S rDNA signal was newly detected at terminal region in the short arm of certain chromosome 1 in A-genome, and at interstitial-distal region in the long arm of chromosome 5 in both genomes. These findings provide a proof and theoretical support for tree peony polyploid breeding, and an accurate karyotyping method for genetic research of plants in Paeonia. [ABSTRACT FROM AUTHOR]

Highlights • The high density genetic map from a cross of ' P. ostti "Fengdan Bai" × P. suffruticosa 'Xin Riyuejin' was constructed. • A total of 3868 markers were mapped covering a genome length of 13175.5 cM. • We detected 6 QTLs of flower-related traits, including 1 QTL for flower number, 2 QTLs for petal length, 2 QTLs for petal number, and 1 QTL for flowering stage in tree peony. • The research will provide guidance for the molecular breeding of the tree peony. Abstract Tree peony (Paeonia suffruticosa Andrews.) is an important ornamental and medicinal plant in China. However, the genetic mechanisms controlling the traits of interest have not been extensively investigated. In this study, an F1 hybrid population, derived from the cross of P. ostti ('Feng Dan') as the female parent and P. suffruti cosa ('Xin Riyuejin') as the male parent, was used to construct the genetic linkage map using genotyping-by-sequencing (GBS) technique. From the high–throughput sequencing, a total of 243.35 Gb raw data were generated. And then 257,335,738 high-quality GBS markers were detected. Finally, an integrated genetic map containing 3868 markers was constructed, which distributed on 5 linkage groups (LGs). The genetic linkage map spanned 13175.5 cM with an average distance of 3.406 cM between adjacent markers. Based on this map, QTL analysis was performed. A total of 6 QTLs for 4 phenotypic traits of flower number, petal length, petal number and flowering stage were detected. This high-density genetic linkage map and QTL mapping for important flower-related traits using GBS with an F1 population of tree peony in this study will provide a solid foundation for gene positional cloning and molecular marker-assisted breeding in the near future. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Pollen sources affect the accumulation of fatty acid during seed development. • FAD3 plays an important role in biosynthesis of α -linolenic acid (ALA). • The action of sequential desaturase genes could be enhanced by suitable pollen. • The impacts of pollen sources were at morphological, chemical and molecular levels. Abstract Tree peony has been widely planted as an excellent oil crop with high proportion of α -linolenic acid (ALA) in its seeds. It was reported that pollen sources have clear effects on fatty acid (FA) composition of its kernels. Nevertheless, the molecular basis of this novel phenomenon is poorly understood. In this study, four Paeonia suffruticosa cultivars whose pollen caused significant differences in ALA content of Paeonia rockii were selected as pollen donors and grouped under high and low ALA groups. After pollination, total FAs content, composition and expression profiles of 10 genes involved in the FA and triacylglycerol (TAG) biosynthetic pathways were investigated during seed development. During the rapid oil accumulation in seeds, three desaturase genes (SAD, FAD2, FAD3) showed much higher expression in high ALA group, and their differential expression profiles corresponded well with the variations in ALA content among different pollen sources. Overall, pollen sources could affect the expression level of genes associated with fatty acid modification and subsequently affect the composition of FA in the kernels. [ABSTRACT FROM AUTHOR]

• Biochar application conferred high-temperature tolerance to tree peony. • Biochar application increased rhizosphere microbial abundance. • Biochar application enhanced reactive oxygen species scavenging capacity. • Biochar application decreased membrane lipid peroxidation and increased photosynthetic capacity. High temperatures due to global warming threaten agricultural production. The application of biochar may enhance plant growth and soil fertility, but whether it exerts an influence on plants under high-temperature stress has not been confirmed. In this study, the effects of biochar on physiological and biochemical indices of high-temperature tolerance were evaluated in the tree peony. It was found that biochar application reduced temperature-induced injury, especially 50% biochar, which was significantly better than 100% biochar in terms of phenotypic changes, stress physiological index and rhizosphere microbial abundance. First, biochar application prevented the decreases in chlorophyll content, and restrained the increases in relative electrical conductivity, malondialdehyde content and reactive oxygen species. Moreover, four antioxidant enzymes showed increased activation in response to biochar application. Furthermore, biochar application enhanced photosynthesis and maintained intact anatomical structures. Additionally, the related physicochemical properties and soil enzyme activities, together with nitrogen, phosphorus and kalium content of cultivation substrate were improved in response to biochar application, while the rhizosphere microbial abundance was increased, which promoted the root of tree peony to grow. These results revealed that biochar could improve high-temperature tolerance of plants, suggesting that the use of biochar is feasible for enhancing plant growth under high-temperature stress. [Display omitted] [ABSTRACT FROM AUTHOR]

Tree peony is a well-known ornamental plant, and its dormancy is a biological characteristic and a necessary process before bud sprouting and flowering. Carbohydrate metabolism plays an important role in regulating many physiological processes of plants. With the extension of chilling treatment, morphology changes indicated that the percentages of sprouting and blossom increased, and nearly 100 percentages of the apical buds sprouted and then blossomed after 21 d 0–4 °C artificial chilling duration. Sufficient chilling fulfillment significantly increased the total respiration rate. Ten putative respiratory metabolism and starch degradation-related genes including PsAMY , PsBMY , PsHK , PsPFK , PsPK , PsPDH , PsIDH , PsOGDH , Ps6PGDH and PsG6PDH were isolated, and the qPCR results indicated that chilling duration induced their expressions and most of them reached the maximum value after 21 d chilling exposure. The activities of the three key enzymes of EMP, TCA and PPP pathway, HK, IDH and G6PDH, were consistent with the expression levels of the corresponding genes ( PsHK , PsIDH and PsG6PDH ). Although the related genes of EMP were up-regulated and the activities of key enzymes increased, but the contribution of EMP gradually decreased during dormancy release in tree peony, and the increasing contribution of PPP pathway was higher than that of TCA pathway. Our results suggested that the activation of PPP pathway might play an important role in chilling-induced dormancy release of tree peony. [ABSTRACT FROM AUTHOR]

• Adventitious root formation of tree peony can be divided into three stages: induction (0–10 d), initiation (10–15 d) and extension (15–30 d). • IAA is the most important promoting hormone, and changes in its content are closely related to adventitious root primordia. • ZR and GAs may act synergistically with IAA to regulate the formation and differentiation of adventitious root primordia. • ABA is related to the stress resistance of in vitro shoots. • Genes like GH3.6, SAUR23, PYL4, PYL11, PIF4, GDP1 and CRD regulate adventitious root formation through the combined regulation of endogenous IAA, GAs, ZR and ABA contents. The difficulty of rooting is the bottleneck of micropropagation in tree peony. Endogenous hormone is the key factor to regulate adventitious roots formation, but the research on the exploration of its related mechanisms is still lagging. In this study, the changes in endogenous hormone content during adventitious root formation were investigated in Paeonia × lemoinei 'High Noon'. Transcriptome sequencing was carried out at five key time points of rooting. The results showed that the in vitro adventitious roots of tree peony formed from induced root primordium, which mainly originated from vascular bundles. However, a few roots originated from the callus. The progress of adventitious root formation can be divided into three stages. IAA (3-Indoleacetic Acid), ZR (trans-Zeatin-riboside), and GAs (Gibberellins) were positively correlated with adventitious root primordia. The trend of ABA (Abscisic Acid) and IAA was opposite, and ABA is related to the stress resistance of in vitro shoots. Plant hormone signal transduction was identified as a key metabolic pathway regulating adventitious root formation. Twenty-eight key genes were mined in this pathway. Using weighted gene co-expression network analysis, 17 hub genes were identified in the co-expression network of hormone trait-related modules. Through a comprehensive analysis, a hypothesis model of endogenous hormones regulating adventitious root formation in tree peony was preliminarily constructed. The results of this study can provide rich genetic resources and a direction for further exploring the molecular mechanism of adventitious root formation in tree peony. [ABSTRACT FROM AUTHOR]

Phenolic acids, the most common plant secondary metabolites, are involved in controlling adventitious root formation and development. Plantlets of tree peony ( Paeonia suffruticosa ), a phenolic acid-rich plant, are generally difficult to root in vitro . In this study, 12 phenolic acids were detected in seedlings of tree peony; the most abundant was paeonol, followed by acetovanillone, paeoniflorin, benzoic acid, methyl gallate, gallic acid, shikimic acid, 4-hydroxybenzoic acid, 2,3-dihydroxy-4-methoxyacetophenone, caffeic acid, chlorogenic acid, and catechol. Paeonol, catechol, and 2, 3-dihydroxy-4-methoxyacetophenone were not detected in tree peony plantlets in vitro . During rooting, caffeic acid, methyl gallate, and paeoniflorin contents remained at high levels, whereas the acetovanillone content remained low. Treatment with caffeic acid (1 mg L −1 ) had the strongest effect on rooting percentage, resulting in an increase from 10% to 64.03%. High indole-3-acetic acid levels were required for root induction in tree peony plantlets in vitro . We concluded that changes in the contents of endogenous phenolic acids (caffeic acid, methyl gallate, paeoniflorin, and acetovanillone) are closely related to rooting of tree peony in vitro , and that exogenous triphenols and especially diphenols are advantageous for rooting in vitro . [ABSTRACT FROM AUTHOR]

In this study, an F 1 population derived from a cross of P. ostti ‘Feng Dan’ × P. suffruticosa ‘Xin Riyuejin’ was used to construct a genetic map for tree peony based on simple sequence repeat (SSR) markers. A total of 705 pair primers were used and finally 124 pair polymorphic primers were screened for the construction of the genetic map. The constructed map contained 35 SSR markers with total length of 338.2 cM, covering 5 linkage groups, of which ranging from 29.8 cM to 120.9 cM in length and including 3–14 markers, .the average distance between each marker was 9.7 cM. Finding the shortest and longest distance between two adjacent markers were 1.4 cM and 37.5 cM, respectively. Furthermore, by the interval mapping (IM) method, 11 QTLs were detected that were related to the phenotypic traits which were investigated among nineteen phenotypic traits of the F 1 progenies in 2014 and 2015, and the range of explained the phenotypic variance was from 9.60% to 46.2%. Among 11 QTLs, the number of characters that were associated with the shoot number, leaf length, flower number, pod height, pod diameter and flower diameter was range from 1 to 4 loci. In conclusion, this genetic map constructed with simple sequence repeat (SSR) markers would be a base for the further molecular breeding study in tree peony. [ABSTRACT FROM AUTHOR]

• The flowering time related gene PoFLC encoded 178 amino acids was cloned in Paeonia ostii 'Fengdan'. • PoFLC presented higher expression levels at initial flowering and half opening stage in Paeonia ostii 'Fengdan'. • Subcellular localization analysis revealed PoFLC was localized in nucleus. • Overexpression of PoFLC in Arabidopsis demonstrated that the bolting and flowering time of transgenic plants were significantly later than wild type. • It is speculated that PoFLC might play an important role in delaying flowering in Paeonia ostii 'Fengdan'. Tree peony is a traditional ornamental flower, but the extremely short flowering period greatly limits their ornamental value. Flowering time related gene PoFLC encoded 178 amino acids was cloned from petals of Paeonia ostii 'Fengdan' based on the third-generation full-length transcriptome sequence. Then, expression profiles of PoFLC in different flower developmental stages and different tissues were analyzed using quantitative real-time PCR (qRT-PCR). The half opening stage showed the highest relative expression level of PoFLC during different flower developmental stages, while the petal showed the highest relative expression level of PoFLC in different tissues. Subcellular localization analysis presented PoFLC was localized in the nucleus. The overexpression vector of PoFLC was constructed and T 2 generation transgenic Arabidopsis were obtained. The bolting time and flowering time of transgenic plants were significantly later than wild type. It is speculated that the formation of late-flowering phenotype in transgenic Arabidopsis might relate to the overexpression of PoFLC. It is anticipated that PoFLC might play an important role in delay flowering, and the results might provide a theoretical basis for further study on the role of PoFLC in regulation flowering period, and benefit the future molecular breeding researches of tree peony. [ABSTRACT FROM AUTHOR]

• Early-flowering mutant of Paeonia ostii 'Fengdan' was observed. Flowering phenotype of early-flowering mutant of Paeonia ostii 'Fengdan', Paeonia ostii 'Fengdan' and Paeonia suffruticosa 'Lianhe' were investigated and characterized. • SNP and InDel Variants associated with early-flowering phenotype using early- and late-flowering tree peony genotypes were conducted by Whole genome re-sequencing and transcriptome integrated analysis. • DEGs harboring SNPs and Indels variants mainly enriched in phenylpropanoid biosynthesis, flavonoid biosynthesis, plant hormone signal transduction, RNA degradation, and MAPK signaling pathways were identified and validated. Tree peony, a traditional ornamental flower and candidate national flower of China, has thousands of varieties with different flower colors and types after a long history of natural selection and artificial breeding. However, the short and concentrated florescence period and a shortage of early- and late-flowering varieties limit the enhancement of ornamental values. Single nucleotide polymorphisms (SNPs) and insertion/deletion mutations (InDels) are important factors for mutant genotypes generation. Whole genome resequencing and transcriptome integrated analysis was conducted using early-flowering genotype Paeonia ostii 'Fengdan' (FD), early-flowering mutant of Paeonia ostii 'Fengdan' (MU), and late-flowering genotype Paeonia suffruticosa 'Lianhe' (LH) to identify variants related to the early-flowering phenotype. Comparison of FD vs LH, MU vs LH, and MU vs FD revealed 1,488 SNPs, 1,261 InDels, and 1,912 differential expressed genes (DEGs) specific to early-flowering genotype FD and MU, respectively. Additionally, 329 DEGs affected by SNPs and InDels variants were differentially expressed in three tree peony genotypes at the full-blooming stage. Furthermore, 37 DEGs affected by SNP variants and 44 DEGs affected by InDel variants were identified in the early-flowering genotype FD and its corresponding MU at the full-blooming stage. Most of these genes were related to phenylpropanoid biosynthesis, flavonoid biosynthesis, plant hormone signal transduction, RNA degradation, and MAPK signaling pathway. Additionally, four SNPs were validated in FD, MU, and LH by Sanger sequencing. Expression profiles of 25 DEGs containing SNP/Indels associated with the early-flowering trait were verified by RT-qPCR. The abundant genetic variations identified in this study offer valuable genomic resources for ongoing functional and molecular breeding research for the early-flowering breeding of tree peony. [ABSTRACT FROM AUTHOR]

• Partial defoliation fails to trigger bud development or reflowering in tree peony. • Complete defoliation triggers sucrose metabolism and rebalances of source-sink relationship. • The reflowering inducing was scarcely related to stress signal. • Photosynthesis itself may be not involved in this process, neither. • Transcriptional regulation of SUTs, SWEETs and INVs is involved in the process. Tree peony (Paeonia suffruticosa Andr.) has a short and concentrated natural fluorescence, and forcing culture is frequently used for its annual production. We previously found that defoliation is critical for tree peony to reflower in the autumn. In this study, we investigated how defoliation induced this process in more detail. We found that partial defoliation with only three top leaves remaining failed to trigger bud development or reflowering. Furthermore, complete defoliation, but not partial defoliation, decreased the contents of sucrose in buds, as well as increasing the contents of glucose and fructose in buds and leaves. Therefore, sucrose metabolism, particularly its hydrolysis, may function as a switch for tree peony reflowering, which is triggered by complete defoliation. Since the complete and partial defoliation treatments produced similar physical damage to plants, the induction of reflowering was unlikely to be related to a stress signal. In addition, the net photosynthetic rates of mature and newly grown young leaves in partial and complete defoliation groups, respectively, were lower than those of the control. Thus, photosynthesis itself may not be involved in this process. At the transcriptional level, defoliation treatment, but not partial defoliation, significantly induced PsSUT1 and PsSWEET12 expression. This was accompanied by the reduction of PsSWEET7 at 24 d in buds, which could facilitate the transfer of sucrose from the leaves to buds. PsCIN3, PsVIN1 and PsVIN2 were also substantially induced by defoliation treatment rather than partial defoliation, which should be mainly involved in sucrose metabolism. In short, complete defoliation is essential for tree peony reflowering in the autumn by triggering sucrose metabolism, as well as rebalancing the source-sink relationship in buds and leaves. [ABSTRACT FROM AUTHOR]

• Rooting response was not affected by stem girding and strangulation. • Strangulation (A) is easy and convenient as compared to stem girdling (B).▪ • The number and length of the primary roots of 'Xiang Yu' is increased responding to the interaction between stem wounding and IBA treatments. • Strangulation and 500–1200 mg/L IBA is recommended to increase the efficacy of mass propagation. • New plants of 'Luoyang Hong' (A) and 'Xiang Yu' (B) following separating shoots after root formation showing terminal flower bud (insert).▪ The tree peony (Paeonia suffruticosa Andr.) is a deciduous woody perennial endemic to Central Plains, Northwest, and Southern Yangtse, China, and is loved by the general public, horticulturists and gardeners all over the world. Tree peonies cultivars are usually propagated vegetatively by grafting and division; however, these methods are inefficient for mass-propagation. Two stem wounding methods (stem girdling and strangulation) and four concentrations of 4-(1 H -Indol-3-yl) butanoic acid (IBA) (0, 500, 1200, and 2000 mg/L) treatments were evaluated in 'Luoyang Hong', 'High Noon', 'Xiang Yu' and 'Fugui Mantang' to find an effective and easy method of mass-propagation. Shoots that rooted while attached to the branches were separated from the branches and transplanted to access the success rates of propagation. The cultivar had significant effects on all root rooting responses. However, stem girdling and strangulation did not affect the root formation responses. Root formation parameters (the number, length, and diameter of the primary roots), especially of 'Xiang Yu', were improved in response to the interaction between stem wounding and IBA treatments. The survival percentage exceeded 61% when rooted plants were transplanted, except for 'High Noon'. It is recommended to propagate tree peonies with stem strangulation and 500–1200 mg/L IBA to increase the efficacy of mass propagation. [ABSTRACT FROM AUTHOR]

The seeds of tree peony have a strict dormancy characteristic, which seriously affects seed germination rate and seedling emergence uniformity. Abscisic acid (ABA) is one of the most important plant hormones regulating seed maturation and dormancy. In this study, the seeds of tree peony ( Paeonia ostii ‘Feng Dan’) were collected at different days after pollination (DAP), and the morphological, physiological and hormonal changes as well as five ABA biosynthetic genes expression were determined in seeds. The results indicate that the soluble sugar, starch and soluble protein contents as well as rooting rate were increased to different degrees; whereas, ABA content increased in the early and middle stages and then decreased later. At transcriptional levels, PoNCED1 and PoZEP1 probably together have a rate-limiting function in ABA biosynthesis with a division of roles, and PoSDR1 may induce substantial ABA biosynthesis in the middle and late development stages; furthermore, PoCHY1 should have multiple functions and PoAAO1 acts as a drought induced gene. This is the first report of ABA biosynthesis in the seeds of tree peony, and it will enable the role of ABA in seed dormancy and germination to be better understood. Furthermore, it may offer help by enhancing tree peony breeding efficiency. [ABSTRACT FROM AUTHOR]

The genetic diversity and relationships among 64 tree peony (Paeonia suffruticosa) germplasm of different colors were analyzed using conserve DNA-derived polymorphism (CDDP) markers. Of 16 primers screened, 13 primers could produce unambiguous and reproducible bands. Using 13 designed CDDP primers, 152 bands were generated with an average of 11.69 bands per primer among 64 accessions, with 149 (98.03%) being polymorphic. Further, accession-specific markers were observed in eight accessions. There was a significant positive correlation between the resolving power (Rp) of each primer and the number of accessions identified (r=0.96, **P<0.01). 64 accessions were clustered by UPGMA into 5 major groups at a similarity index value of 0.69 based on the CDDP marker data. Clustering of tree peony germplasm corresponded to origins and Zhongyuan group cultivars mainly based on flower color. The results demonstrated that the CDDP marker system and designed primers were efficient for the identification and genetic relationship analysis of tree peony genotypes. It is the first time that CDDP marker targeted flower color by gene-targeted primers and successfully made tree peony accessions cluster based on flower color. The results provide useful information for the utilization of gene-targeted molecular markers on cultivar identification and genetic relationship analysis in plants. [ABSTRACT FROM AUTHOR]

Highlights: [•] Glucose delays senescence and extends vase life of cut P. suffruticosa flowers. [•] Glucose inhibits climacteric ethylene production of cut P. suffruticosa flowers. [•] Glucose impairs ethylene biosynthetic activities by repressing PsACS1 expression. [•] Glucose reduces the sensitivity of cut P. suffruticosa flowers to ethylene. [ABSTRACT FROM AUTHOR]

Highlights: [•] This is the first attempt to use Paeonia ostii as materials to develop SSR markers in Paeonia. [•] We developed 12 novel polymorphic SSR markers in tree peonies and test their cross-amplification in two herbaceous peony species (Paeonia veitchii and Paeonia lactiflora). [•] Genetic relationships among 53 accessions, including 8 species and 40 cultivars of tree peonies and 5 accessions of herbaceous species/cultivars, were studied based on the 12 polymorphic SSR markers. [ABSTRACT FROM AUTHOR]

Abstract: With rich germplasm resources, species of the genus Paeonia are exceptionally diverse in their flower color, flower type, plant height and so on. It is also well known that the genus has important ornamental and medicinal values. Hence, many researches especially Chinese take great efforts to study the genetic diversity. Even so, complex genetic backgrounds, vague genetic relationships and mixed cultivars still give rise to severe restrictions in breeding programmes. This review discusses recent literature on genetic diversity of Paeonia sect. Moutan DC and sect. Paeonia, which contain relatively rich germplasm resources from the level of comparative morphology, palynology, cytology, isozyme and molecular markers and DNA sequence analysis. Meantime, the advance research direction of genetic diversity in Paeonia is proposed. Comprehensively utilizing evidence in many levels and balanced development between tree peony and herbaceous peony are highlighted. [Copyright &y& Elsevier]

• Oil tree peony self-compatibility, low seed setting rate, highly dependent on bee pollination. • Bee pollination is a more effective way to increase oil tree peony production than artificial pollination (fruit yield increased by 56.28% and oil yield increased by 12.24%). • Bee pollination accelerates fruit growth and produces bigger and heavier fruits. Insufficient pollination reduces the fruit and seed setting rate and limits the chance of outcrossing in crop plants that are highly dependent on insect pollination, thus affecting the quality and growth rate of progenies. To investigate the effect of pollination methods on the fruit growth rate, fruit yield, oil yield and seed oil quality, four pollination methods, such as (1) in cages with honeybees (Apis mellifera L.), the control in cages with (2) hand pollination, (3) wind pollination, and (4) self-pollination were used to pollinate the flowers of oil tree peony (Paeonia ostii T. Hong et J.X. Zhang). Results showed that the mean growth rate and cumulative growth rate of fruit diameter, follicle length and diameter pollinated by honeybees were significantly higher than that of the control group (hand, wind and self-pollination). Fruit development ratio, seed setting rate and the number of seeds per fruit pollinated by honeybees were significantly higher than self-pollination. Moreover, pollination by honeybees increased yield per fruit by 56.28%, 59.42% and 126.27% compared to the hand, wind and self-pollination, respectively. Compared with hand pollination, the oil yield of honeybee-pollinated tree peony increased by 12.24%. However, the total unsaturated fatty acidcontent of seed oil was not significantly changed with different pollination methods. Our study demonstrated that bee pollination is essential to reach rapid fruit development and high seed yield in oil tree peony. [ABSTRACT FROM AUTHOR]

Abstract: Bud sports have been widely exploited for creating novel cultivars in vegetatively propagated plants. However, bud sports of tree peony have rarely occurred nor been applied to breeding. We used sequence related amplified polymorphism (SRAP) markers to characterize two tree peony groups with bud sports. ‘Er Qiao’ and ‘Luo Yang Hong’ formed group I and are derived from Chinese cultivars, while ‘Shima-nishiki’ and ‘Taiyō’ formed group II and are related to Japanese cultivars. The DNA samples were evaluated with 25 different primer pairs. This resulted in a total of 149 different amplicons in Group I, of which 80.5% were polymorphic. Group II generated a total of 57 amplicons, of which 63.2% were polymorphic. The two groups shared 43 amplicons. The genetic similarity among the cultivars ranged from 0.33 to 0.60. The two bud sports groups were apparently separated on the unweighted pair-group method with arithmetic averages cluster analysis tree. The results demonstrated that this marker system appeared effective in detecting molecular differences between original parents and their bud sports in tree peony. This study provides a technical base for characterizing plants with bud sports, which are valuable genetic resources for further breeding. [Copyright &y& Elsevier]

Abstract: A comparison in non-blotches and blotches of 35 cultivars of Xibei tree peony was investigated to explore flower coloration of Xibei tree peony (the second cultivar group in Chinese tree peony). With high performance liquid chromatography (HPLC) analysis, six anthocyanins including peonidin 3,5-di-O-glucoside (Pn3G5G), peonidin 3-O-glucoside (Pn3G), cyanidin 3,5-di-O-glucoside (Cy3G5G), cyanidin 3-O-glucoside (Cy3G), pelargonidin 3,5-di-O-glucoside (Pg3G5G), and pelargonidin 3-O-glucoside (Pg3G) were detected in non-blotches and blotches of petals. Total anthocyanins (TA), total flavones and flavonols (TF), and the copigmentation index (CI) were also analyzed. Cyanidin-based glycosides, which accumulated abundantly at the basal petal, resulted in blotch formation. Some peculiar cultivars with only one kind of anthocyanins or without anthocyanins in non-blotches were found in this study. For example, ‘Feng Zi Xiu Se’, ‘Ou Duan Si Lian’, and ‘Xi Wang’ contained only Pn3G5G; ‘Bing Shan Cang Yu’ and ‘Jin Bo Dang Yang’ contained only Cy3G; while no anthocyanins were found in ‘Bing Shan Xue Lian’. Several cultivars were rich in Pg-based glycosides, such as ‘Ni Hong Huan Cai’, and ‘Ju Yuan Shao Nv’. These cultivars would be excellent parents for creating new cultivars with novel flower color in the future. [Copyright &y& Elsevier]

Tree peony (Paeonia Sect. Moutan) is widely grown as an ornamental plant and is known for its 'National Beauty and Heavenly Fragrance '. However, the genetic improvement of floral scent traits is fundamentally limited by the paucity of genomic marker resources. Given the large-scale development of microsatellite markers using transcriptome sequences, we conducted an association analysis to identify microsatellite markers associated with main floral components. A total of 8,443 EST-SSRs were identified, with an average of one SSR per 15.55 kb. Di-nucleotide repeats were the most plentiful repeat type, followed by tri-, tetra-, penta- and hexa-nucleotide repeats. Among 969 synthesized primer pairs, 499 were successfully amplified and 136 showed polymorphism which exhibited relatively high levels of transferability were observed across 12 individuals in the genus Paeonia , thus expanding their utility. Subsequently, 31 polymorphic EST-SSR markers were selected for the analysis of genetic diversity and population structure, resulting in 176 alleles; the polymorphism information content (PIC) varied from 0.31 to 0.87. According to the population structure analysis, the association varieties were divided into three subgroups. Finally, single marker-trait association analysis based on mixed linear model (MLM) identified 29 significant associations, involving five floral components with 18 SSRs and a low proportion of phenotypic variance ranging from 4.57 to 23.46%. The newly developed markers were valuable resources that could provide a powerful genomic tool for genetic studies and accelerate the process of molecular marker-assisted breeding of tree peony floral scent. [ABSTRACT FROM AUTHOR]

Abstract: The effect of a new light source, cold cathode fluorescent lamps (CCFLs), on the growth of peony (Paeonia suffruticosa cv. ‘Wu Long Peng Sheng’) plantlets in vitro was examined in six different light quality ratios: 100% red (R), 80% R+20% blue (B), 70% R+30% B, 60% R+40% B, 100% B and white CCFLs. Control illumination was provided by conventional heat-generating plant growth fluorescent lamps (PGFLs). All plantlet growth parameters were as effective under 70% R+30% B (the best performing CCFL ratio) as they were under PGFLs. Chlorophyll content (a, b and total) was greater in the range of 60–80% R+20–40% B, although in general there were no significant differences between the best performing R:B ratio and PGFLs. This study indicates that CCFLs can be used as effectively – if not better – than conventional PGFLs to micropropagate this woody ornamental. [Copyright &y& Elsevier]