Search

Tree peonies native to China are a precious crop with ornamental, medicinal and edible oil properties, of which flare tree peony (Paeonia rockii) is one of the most significant germplasms in Paeonia. The development and application of expressed sequence tag-simple sequence repeat (EST-SSR) markers are very valuable for genetic and breeding applications, but EST-SSR resources for the genus Paeonia are still limited. In this study, we first reported the development of SSRs within transcription factors (TFs) in P. rockii based on next-generation sequencing (NGS) and single-molecule long-read sequencing (SMLRS). A total of 166 EST-SSRs containing six nucleotide repeat types were identified from 959 candidate TFs associated with yield, with an average of one SSR per 5.83 unigenes. In total, 102 (61.45%) pairs of primers produced amplification products in the two RNA-seq cultivars. Among them, 58 (56.86%) pairs of primers from 18 gene families (AP2, bHLH, HSF, etc.) were identified to be polymorphic both in the parents of a linkage mapping population and in eight randomly selected accessions of P. rockii. Further, the 58 EST-SSRs indicated a high level of informativeness with PIC values ranging from 0.32 to 0.91 (mean 0.70) after assessment in 37 tree peony accessions. Transferability studies indicated that the amplification ratio of the 58 pairs of primers ranged from 89.66 to 100% across seven species of Paeonia. In addition, a genetic relationship study was performed in 62 accessions. Cluster analysis using the neighbour-joining (NJ) tree demonstrated that major clusters corresponded to the known pedigree trees. Taken together, these newly developed EST-SSRs have a potential use in the conservation of tree peony germplasm and marker-assisted selection (MAS) breeding.

Abstract Determining the factors promoting speciation is a major task in ecological and evolutionary research and can be aided by phylogeographic analysis. The Qinling–Daba Mountains (QDM) located in central China form an important geographic barrier between southern subtropical and northern temperate regions, and exhibit complex topography, climatic, and ecological diversity. Surprisingly, few phylogeographic analyses and studies of plant speciation in this region have been conducted. To address this issue, we investigated the genetic divergence and evolutionary histories of three closely related tree peony species (Paeonia qiui, P. jishanensis, and P. rockii) endemic to the QDM. Forty populations of the three tree peony species were genotyped using 22 nuclear simple sequence repeat markers (nSSRs) and three chloroplast DNA sequences to assess genetic structure and phylogenetic relationships, supplemented by morphological characterization and ecological niche modeling (ENM). Morphological and molecular genetic analyses showed the three species to be clearly differentiated from each other. In addition, coalescent analyses using DIYABC conducted on nSSR variation indicated that the species diverged from each other in the late Pleistocene, while ecological niche modeling (ENM) suggested they occupied a larger area during the Last Glacial Maximum (LGM) than at present. The combined genetic evidence from nuclear and chloroplast DNA and the results of ENM indicate that each species persisted through the late Pleistocene in multiple refugia in the Qinling, Daba, and Taihang Mountains with divergence favored by restricted gene flow caused by geographic isolation, ecological divergence, and limited pollen and seed dispersal. Our study contributes to a growing understanding of the origin and population structure of tree peonies and provides insights into the high level of plant endemism present in the Qinling–Daba Mountains of Central China.

Abstract 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.

Abstract Paeonia ostii, a member of tree peony, is an emerging oil crop with important medical and oil uses and widely cultivated in China. Dissolving the genetic diversity and domestication history of this species is important for further genetic improvements and deployments. We firstly selected 29 simple sequence repeats (SSRs) via transcriptome mining, segregation analyses and polymorphism characterizations; then, 901 individuals from the range-wide samples were genotyped using well-characterized SSR markers. We observed moderate genetic diversity among individuals, and Shaanxi Province was identified as the center of genetic diversity for our cultivated plants. Five well-separated gene pools were detected by STRUCTURE analyses, and the results suggested that multiple independent domestication origins occurred in Shaanxi Province and Tongling City (Anhui Province). Taken together, the genetic evidence and the historical records suggest multiple long-distance introductions after the plant was domesticated in Shandong, Henan and Hunan provinces. The present study provides the first genetic evaluation of the domestication history of P. ostii, and our results provide an important reference for further genetic improvements and deployments of this important crop.

Genetic linkage maps, permitting the elucidation of genome structure, are one of most powerful genomic tools to accelerate marker-assisted breeding. However, due to a lack of sufficient user-friendly molecular markers, no genetic linkage map has been developed for tree peonies (Paeonia Sect. Moutan), a group of important horticultural plants worldwide. Specific-locus amplified fragment sequencing (SLAF-seq) is a recent molecular marker development technology that enable the large-scale discovery and genotyping of sequence-based marker in genome-wide. In this study, we performed SLAF sequencing of an F1 population, derived from the cross P. ostti 'FenDanBai' × P. × suffruticosa 'HongQiao', to identify sufficient high-quality markers for the construction of high-density genetic linkage map in tree peonies. After SLAF sequencing, a total of 78 Gb sequencing data and 285,403,225 pair-end reads were generated. We detected 309,198 high-quality SLAFs from these data, of which 85,124 (27.5%) were polymorphic. Subsequently, 3518 of the polymorphic markers, which were successfully encoded in to Mendelian segregation types, and were in conformity with the criteria of high-quality markers, were defined as effective markers and used for genetic linkage mapping. Finally, we constructed an integrated genetic map, which comprised 1189 markers on the five linkage groups, and spanned 920.699 centiMorgans (cM) with an average inter-marker distance of 0.774 cM. There were 1115 'SNP-only' markers, 18 'InDel-only' markers, and 56 'SNP&InDel' markers on the map. Among these markers, 450 (37.85%) showed significant segregation distortion (P < 0.05). In conclusion, this investigation reported the first large-scale marker development and high-density linkage map construction for tree peony. The results of this study will serve as a solid foundation not only for marker-assisted breeding, but also for genome sequence assembly for tree peony.

Tree peonies are important ornamental plants worldwide, but growing them can be frustrating due to their short and concentrated flowering period. Certain cultivars exhibit a reblooming trait that provides a valuable alternative for extending the flowering period. However, the genetic control of reblooming in tree peonies is not well understood. In this study, we compared the molecular properties and morphology of reblooming and non-reblooming tree peonies during the floral initiation and developmental processes. Using transcriptome sequencing technology, we generated 59,275 and 63,962 unigenes with a mean size of 698 bp and 699 bp from the two types of tree peonies, respectively, and identified eight differentially expressed genes that are involved in the floral pathways of Arabidopsis thaliana. These differentially regulated genes were verified through a detailed analysis of their expression pattern during the floral process by real time RT-PCR. From this combined analysis, we identified four genes, PsFT, PsVIN3, PsCO and PsGA20OX, which likely play important roles in the regulation of the reblooming process in tree peonies. These data constitute a valuable resource for the discovery of genes involved in flowering time and insights into the molecular mechanism of flowering to further accelerate the breeding of tree peonies and other perennial woody plants.

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.Twenty wild populations were sampled from the distributional range of P. rockii. Significant population differentiation was suggested (F(ST) value of 0.302). Moderate genetic diversity at the population level (H(S) of 0.516) and high population diversity at the species level (H(T) of 0.749) were detected. Significant excess homozygosity (F(IS) 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

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. yananensis (=P. × yananensis) is of hybrid origin, with P. jishanensis as a maternal parent and P. rockii as a paternal parent. Our success in documenting the hybrid origin of P. yananensis suggests that combined evidence from morphology, maternally inherited cpDNA, and biparentally inherited microsatellites could serve as a powerful tool in hybrid studies. [ABSTRACT FROM AUTHOR]

Premise of the study: Microsatellite (simple sequence repeat, SSR) primers were developed for the Chinese peony, P. lactiflora, 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 amplified 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. [ABSTRACT FROM AUTHOR]