Genetic Diversity of Phyllanthus emblica From Two Different Climate Type Areas

Suitability mapping of native tree species in dry-hot valleys of Yunnan based on InVEST-MaxEnt coupled modeling: model validation framework with native tree species actual distribution and seed germination

Introduction

The target valleys along the Jinsha, Nujiang, Lancang, and Yuanjiang Rivers exhibit acute human-land conflicts and ecosystem vulnerability. Predicting the distribution of potential suitable habitats for native tree species in Yunnan Province provides basin-scale insights for the management of ecosystems in dry and hot valleys, thereby advancing restoration planning in dry-hot valleys.

Methods

This study investigates native tree species suitability in Yunnan's dry-hot valleys using an integrated MaxEnt-InVEST modeling framework.

Results

Temperature and precipitation emerged as dominant bioclimatic controls, with optimal species occurrence (1 000-2 500 m) showing negative elevation correlation. Four native tree species (Osteomeles schwerinae, Phyllanthus emblica, Quercus francetii and Sapindus delavayi) displayed fragmented suitable areas along mountainous riparian zones, while habitat quality hotspots mainly covered non-urbanized regions, avoiding central urban clusters and northeastern/southeastern karst zones. The coupled model demonstrated significantly improved accuracy compared to the standalone MaxEnt by incorporating land-use impacts, with Yuanmou County case analysis confirming the enhanced predictive capability through actual distribution patterns. Spatial prioritization identified core planting clusters in central/southeastern valleys, though fragmented by agricultural encroachment.

Discussion

This methodology provides a cost-effective solution for vegetation restoration planning in ecologically fragile dry-hot ecosystems. The research results can provide scientific support for the restoration of degraded ecosystems in dry-hot valleys of Yunnan Province, the national Afforestation program and soil and water conservation projects.

Chromosome-scale genome assembly of Phyllanthus emblica L. 'Yingyu'

Phyllanthus emblica L. is an edible plant with medicinal properties native to the dry-hot valley of Yunnan, China. Here, we report a de novo chromosome-scale genome of P. emblica wild type 'Yingyu'. 'Yingyu' is an octopoid plant with a total of 104 chromosomes. In total, we assembled and clustered 480 Mb of the genome and constructed 26 pseudochromosomes (haplotypes) of P. emblica wild type 'Yingyu' that encompass 97.9% of the genome and demonstrate to have relatively high integrity. We annotated 31,111 genes found in the genome of P. emblica. We screened 5 different tissues for searching the tissue-specific expression candidate genes. Four unknown function candidate genes were expressed at high levels in the flowers while genes relating to the biosynthesis of gibberellins and cellulose were specifically expressed in the fruits. The ascorbate biosynthesis-related genes were screened on P. emblica 'Yingyu' genome. The high expression level of 2 GDP-mannose epimerases and one L-galactono-1,4- lactone dehydrogenases in the fruit may be related to the activity of absorbate biosynthesis in the fruit. The chromosome-level genomic data for P. emblica we report will be important for the development of molecular markers to facilitate the selection of superior cultivars for processing and pharmaceuticals.

Genetically and chemically intraspecific variations of Ficus hirta provide novel insights into its protection and utilization

BACKGROUND

Radix Fici Hirtae, the dry root of Ficus hirta, is a famous ethnomedicine and food that has been widely used by Yao and Zhuang nationalities in southern China for its potent antitumor, antifungal, and hepatoprotective effects. Recently, owing to over-exploitation and habitat destruction, F. hirta has been pushed to the brink of depletion. In addition, cultivation and breeding have resulted in severe intermixing and degeneration over the past 20 years. However, little is known about the genetic background and medicinal quality of F. hirta across populations, which restricts its protection and utilization. In this study, we conducted an evaluation of the chloroplast DNA (cpDNA) genetic diversity and population structure of F. hirta in southern China, and further evaluated its medicinal quality based on HPLC fingerprinting and the content determination of the active components.

RESULTS

F. hirta presented high overall genetic diversity (Hd = 0.792) for cpDNA but low genetic diversity (Hd = 0.000 ~ 0.467) within populations. All seventeen populations were genetically assigned into two groups, most of which were not geographically clustered together. Mantel test revealed no significant isolation by distance pattern for F. hirta (P = 0.233), which might be related to its habitat fragmentation. High population differentiation (FST = 0.912) was detected in F. hirta, and AMOVA revealed that 91.17% of cpDNA variation occurred between populations. HPLC fingerprint analysis indicated that most F. hirta samples derived from 14 geographic origins had highly similar components (similarity = 0.828 ~ 0.975). Fourteen origins of F. hirta were clustered into three groups by HCA, PCA and OPLS-DA. Psoralen and bergapten were the differentiated quality markers among the groups. The medicinal quality of the populations NN, SD and HZ within southwestern group was much greater than that of the ND and GZ populations within southeastern group, which is consistent with the comprehensive quality scores for each origin (Y = 1.78 ~-0.82). The medicinal quality formation of F. hirta was highly correlated with geographical environment but not with cpDNA genetic variation.

CONCLUSIONS

F. hirta presented high overall genetic diversity and population differentiation, but without significant isolation by distance, which might relate to its habitat fragmentation. Different geographic origins' Radix Fici Hirtae were chemically clustered into three groups, which were mainly differentiated by psoralen and bergapten. The medicinal quality of Radix Fici Hirtae exhibited a southwest to southeast variation pattern across southern China, and its quality formation was influenced mostly by geographical environments. Our results provide references for the conservation, core collection construction and improvement of F. hirta.

Comparative Chloroplast Genomes and Phylogenetic Relationships of True Mangrove Species Brownlowia tersa and Brownlowia argentata (Malvaceae)

Brownlowia tersa and Brownlowia argentata are two true mangroves in the genus Brownlowia in Malvaceae, and they are a near-threatened and a data-deficient species, respectively. However, the genomic resources of Brownlowia have not been reported for studying their phylogeny and evolution. Here, we report the chloroplast genomes of B. tersa and B. argentata based on stLFR data that were 159,478 and 159,510 base pairs in length, respectively. Both chloroplast genomes contain 110 unique genes and one infA pseudogene. Sixty-eight RNA-editing sites were detected in 26 genes in B. argentata. A comparative analysis with related species showed similar genome sizes, genome structures, and gene contents as well as high sequence divergence in non-coding regions. Abundant SSRs and dispersed repeats were identified. Five hotspots, psbI-trnS, trnR-atpA, petD-rpoA, rpl16-rps3, and trnN-ndhF, were detected among four species in Brownlowioideae. One hotspot, rps14-psaB, was observed in the two Brownlowia species. Additionally, phylogenetic analysis supported that the Brownlowia species has a close relationship with Pentace triptera. Moreover, rpoC2 was a candidate gene for adaptive evolution in the Brownlowia species compared to P. triptera. Thus, these chloroplast genomes present valuable genomic resources for further evolutionary and phylogenetic studies of mangroves and plant species in Malvaceae.

Investigation of the hypoglycemic bioactive components of Phyllanthi Fructus through biological assessment combined with ultrafiltration affinity mass spectrometry

Phyllanthi Fructus (PF) is a tropical fruit with the potential to effectively reduce postprandial blood glucose. However, the lack of quantitative evaluation methods and comprehensive understanding of hypoglycemic active compounds has hindered the development and application of functional foods and dietary supplements derived from PF. In this study, based on the "mass reaction parallel line method", with acarbose as the control and PF extract as the test material, a biological evaluation method for PF hypoglycemic activity based on α-glucosidase inhibition was established for the first time. The in vitro and in vivo validation experiments showed that the coefficient (r) of correlation between the biological evaluation results and the AUC of rat postprandial blood glucose concentration was as high as 0.866, which confirmed the reliability of the evaluation method. The analysis of 20 batches of PF samples showed that the hypoglycemia potency of PF ranged from 2.66 to 8.39 U mg-1, with an average value of 4.00 U mg-1, and the standard deviation was 1.5. UF-LC-MS was used to identify 36 components of PF capable of binding to α-glucosidase. Molecular docking results showed that the binding energy was between -3.5 and -14.3 kJ mol-1. The hypoglycemic activity of 17 available control products was tested, and 8 inhibitors were found, including hyperoside, gallic acid, and corilagin. Dose-effect analysis suggested that flavonoids and polyphenols with a phenolic hydroxyl structure could inhibit α-glucosidase. In short, this study provides a basis for the development of PF hypoglycemic functional foods.

Climatic factors, but not geographic distance, promote genetic structure and differentiation of Cleistogenes squarrosa (Trin.) Keng populations

Climate can shape plant genetic diversity and genetic structure, and genetic diversity and genetic structure can reflect the adaptation of plants to climate change. We used rbcl and trnL-trnF sequences to analyze the genetic diversity and genetic structure of C. squarrosa under the influence of different environmental factors in Inner Mongolia grassland. The results showed that the genetic diversity of this species was low. (The trnL-trnF sequences have higher genetic diversity than rbcl sequences.) C. squarrosa had low genetic diversity compared to other prairie plants, but had a more pronounced genetic structure. The haplotype network diagram of the combined sequences could be divided into two categories, and the results of the NJ, MP, and ML trees also showed that the haplotypes were divided into two branches. The results of genetic structure analysis showed that that the populations located in the desert steppe fall into exactly one cluster, and the populations located in the typical steppe fall into exactly another cluster. The neutrality tests were all negative and the mismatch distribution also showed a single peak across the population, suggesting that C. squarrosa had undergone population expansion and was well adapted to the local environment. The results of the mantel test showed that climate had a greater influence on the genetic distance of C. squarrosa, with annual precipitation having a higher influence than mean annual temperature. This study provided basic genetic information on the genetic structure of C. squarrosa and contributes to the study of genetic adaptation mechanisms in grassland plants.

Recent advances in the potential of Phyllanthus emblica L. and its related foods for combating metabolic diseases through methylglyoxal trapping

Methylglyoxal (MG) serves as the primary precursor for the nonenzymatic glycation of proteins and DNA, leading to advanced glycation end products (AGEs). Regular intake of dietary MG is strongly correlated with low-grade inflammation, potentially accelerating the pathogenesis of metabolic diseases, including obesity, diabetes, cancers, liver diseases, Alzheimer's disease, cardiovascular diseases, aging, and bone loss. Although pharmaceutical agents (pimagedine and candesartan) have been developed to inhibit MG formation, they often come with serious side effects (nausea, diarrhea, headache, gastrointestinal disturbance, symptomatic hypotension, abnormal renal and liver function tests, development of antinuclear antibody, pernicious-like anemia, and hyperkalemia), highlighting the need for an efficient and safe approach to scavenging MG. Phyllanthus emblica Linn fruit, a nutritious edible fruit, and medicinal plant contains over 300 bioactive compounds. Among twenty-three herbals, 100 μg/mL of the aqueous extract of Phyllanthus emblica fruit (APF) exhibits the highest potency in trapping MG, achieving an 87.3 % reduction under d-fructose induced BSA-AGEs formation. However, there are few reports detailing APF and its related foods' specific impact on disease prevention through MG trapping. This review summarizes the mechanisms through which MG is linked to the development of metabolic diseases and provides several strategies for reducing MG levels using APF and its bioactive compounds. The potential antiglycation properties of APF may offer new applications in the food industry and pharmacological research.

Study on the white frost formation mechanism during storage of Phyllanthus emblica Linn. fruit based on component analysis and spatial metabolomics

The Phyllanthus emblica Linn. fruit (PEF) is a well-known medicinal and food homologous item in tropical Southeast Asian. During the drying and storing processes, some PEF will grow white frost on its surface, which is typically taken as a sign of greater quality. However, the material basis and formation mechanism of white frost on PEF surfaces are currently unclear, and there is no sufficient evidence to support the correlation between white frost on PEF surfaces and their quality. In this paper, high-performance liquid chromatography (HPLC) was used to study the differences in active ingredient content of PEF medicinal materials with and without frost. The microstructure and elemental composition of white frost were studied using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The Fourier transform infrared spectroscopy (FT-IR) was used to analysis the main functional groups in white frost. The ultra-performance liquid chromatography quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS/MS) combined with UNIFI database, EDS and FT-IR results, and reference materials were used to identify the chemical composition of white frost. The exocarp of PEF before and after drying and storage was analyzed by spatial metabolomics using desorption electrospray ionization (DESI) mass spectrometry imaging system to reveal the formation mechanism of white frost on the surface of PEF. The results found that the PEF with frost have higher levels of active ingredients than those without frost. EDS and FT-IR results show that white frost is mainly composed of C, O, K elements, and contains a large number of phenolic hydroxyl, carboxyl etc. UPLC-Q-TOF-MS/MS results found that the main components of white frost were organic acids, fatty acids, and tannins, including quality markers such as gallic acid and ellagic acid etc. Spatial metabolomics research found that the white frost formation mechanism mainly involved in the ascorbate and aldarate metabolism, cutin, suberin and wax biosynthesis, citrate cycle (TCA cycle) and biosynthesis of unsaturated fatty acid. This study reveals the material basis, formation mechanism, and relationship between the surface white frost of PEF and the quality of medicinal materials, providing valuable information for the quality evaluation of PEF.

De novo transcriptome profiling and development of novel secondary metabolites based genic SSRs in medicinal plant Phyllanthus emblica L. (Aonla)

Phyllanthus emblica (Aonla, Indian Gooseberry) is known to have various medicinal properties, but studies to understand its genetic structure are limited. Among the various secondary metabolites, ascorbic acid, flavonoids, terpenoids, phenols and tannins possess great potential for its pharmacological applications. Keeping this consideration, we assembled the transcriptome using the Illumina RNASeq500 platform, generating 39,933,248 high-quality paired-end reads assembled into 1,26,606 transcripts. A total of 87,771 unigenes were recovered after isoforms and unambiguous sequences deletion. Functional annotation of 43,377 coding sequences against the NCBI non-redundant (Nr) database search using BlastX yielded 38,692 sequences containing blast hits and found 4685 coding sequences to be unique. The transcript showed maximum similarity to Hevea brasilensis (16%), followed by to Jatropha curcas (12%). Considering key genes involved in the biosynthesis of flavonoids and various classes of terpenoid compounds, thirty EST-SSR primer sequences were designed based on transcriptomic data. Of which, 12 were found to be highly polymorphic with an average of 86.38%. The average value for marker index (MI), effective multiplicity ratio (EMR), resolution power (Rp) and polymorphic information content (PIC) was 7.20, 8.34, 8.64 and 0.80, respectively. Thus, from this study, we developed newly EST-SSRs linked to important genes involved in the secondary metabolites biosynthesis that will be serving as an invaluable genetic resource for crop improvement including the selection of elite genotypes in P. emblica and its closely related Phyllanthaceae species.

Effects of Climatic Change on Phylogeography and Ecological Niche of the Endemic Herb Elymus breviaristatus on the Qinghai-Tibet Plateau

Past climatic and topographic variations have created strong biogeographic barriers for alpine species and are key drivers of the distribution of genetic variation and population dynamics of species on the Qinghai-Tibet Plateau (QTP). Therefore, to better conserve and use germplasm resources, it is crucial to understand the distribution and differentiation of genetic variation within species. Elymus breviaristatus, an ecologically important rare grass species with strong resistance, is restricted to a limited area of the QTP. In this study, we investigated the phylogeography of E. breviaristatus using five chloroplast genes and spacer regions in natural populations distributed along the eastern QTP. We identified a total of 25 haplotypes among 216 individuals from 18 E. breviaristatus populations, which were further classified into four haplogroups based on geographical distribution and haplotype network analysis. Notably, we did not observe any signs of population expansion. High genetic diversity was exhibited at both species and population levels, with precipitation being the main limiting factor for population genetic diversity levels. Higher genetic diversity was exhibited by populations located near the Mekong-Salween Divide genetic barrier, suggesting that they may have served as a glacial refuge. The significant pattern of genetic differentiation by environmental isolation highlights the influence of heterogeneous environments on the genetic structure of E. breviaristatus populations. Additionally, the results of ecological niche models indicated that the geographic distribution of E. breviaristatus populations has decreased rapidly since the Last Glacial Maximum but is not threatened by future global warming.

Genome of Phyllanthus emblica: the medicinal plant Amla with super antioxidant properties

Phyllanthus emblica or Indian gooseberry, commonly known as amla, is an important medicinal horticultural plant used in traditional and modern medicines. It bears stone fruits with immense antioxidant properties due to being one of the richest natural sources of vitamin C and numerous flavonoids. This study presents the first genome sequencing of this species performed using 10x Genomics and Oxford Nanopore Technology. The draft genome assembly was 519 Mbp in size and consisted of 4,384 contigs, N50 of 597 Kbp, 98.4% BUSCO score, and 37,858 coding sequences. This study also reports the genome-wide phylogeny of this species with 26 other plant species that resolved the phylogenetic position of P. emblica. The presence of three ascorbate biosynthesis pathways including L-galactose, galacturonate, and myo-inositol pathways was confirmed in this genome. A comprehensive comparative evolutionary genomic analysis including gene family expansion/contraction and identification of multiple signatures of adaptive evolution provided evolutionary insights into ascorbate and flavonoid biosynthesis pathways and stone fruit formation through lignin biosynthesis. The availability of this genome will be beneficial for its horticultural, medicinal, dietary, and cosmetic applications and will also help in comparative genomics analysis studies.

Phyllanthi Fructus: A modal medicinal and food homologous item in quality evaluation

Phyllanthi Fructus is a highly unique medicine and food homologous item, which exhibits distinctive flavor, notable nutritional value, and abundant pharmacological activity. It has enormous potential in the creation of health products and pharmaceuticals. However, due to the unique laws of quality formation and transfer of Phyllanthi Fructus, its appearance, shape, chemical compositions, nutrients, and sensory flavors are frequently greatly influenced by botanical resources, the processing and storage conditions. As a result, the current quality evaluation model is difficult to meet the needs of Phyllanthi Fructus as a medicine and food homologous item in the development of diversified products. This paper constructs the hierarchical utilization mode of Phyllanthi Fructus based on its unique quality formation and transmission laws, explores the quality evaluation model for food-oriented use and medicinal-oriented use, respectively, and systematically describes the quality evaluation idea under diversified application scenarios. This paper aims to serve as a reference for the construction of a quality evaluation model suitable for the medicine and food homologous item of Phyllanthi Fructus.

Dextran-Sulfate-Sodium-Induced Colitis-Ameliorating Effect of Aqueous Phyllanthus emblica L. Extract through Regulating Colonic Cell Gene Expression and Gut Microbiomes

The anti-inflammation effect of aqueous Phyllanthus emblica L. extract (APE) and its possible underlying mechanism in dextran sulfate sodium (DSS)-induced mice chronic colonic inflammation were studied. APE treatment significantly improved the colitic symptoms, including ameliorating the shortening of the colon, increasing the DSS-induced body weight loss, reducing the disease activity index, and reversing the condition of colon tissue damage of mucus lost and goblet cell reduction. Overproduction of serum pro-inflammatory cytokines were suppressed by the treatment of APE. Gut microbiome analysis showed that APE remodeled the structure of gut bacteria in phylum and genus levels, upregulating the abundance of phylum Bacteroidetes, family Muribaculaceae, and genus Bacteroides and downregulating the abundance of phylum Firmicutes. The reshaped gut microbiome caused metabolic functions and pathway change with enhanced queuosine biosynthesis and reduced polyamine synthesis pathway. Colon tissue transcriptome analysis further elucidated APE-inhibited mitogen-activated protein kinase (MAPK), cytokine-cytokine receptor interaction, and tumor necrosis factor (TNF) signaling pathways and the expressions of the genes that promote the progress of colorectal cancer. It turned out that APE reshaped the gut microbiome and inhibited MAPK, cytokine-cytokine receptor interaction, and TNF signaling pathways as well as the colorectal-cancer-related genes to exert its colitis protective effect.

Determination of the Content of Phenolic Compounds and the Changes of Polyphenol Oxidase and Each Index during Browning of Phyllanthus emblica at Different Storage Temperatures

In order to further study the early browning of P. emblica marker and mechanism, it is necessary for us to measure the changes in the content of some substances to find quality markers during the browning process of P. emblica. So, we simulated the storage conditions under different temperatures, including 5°C, 25°C, and 35°C. And, the contents of some of its phenolic compounds were determined by RP-HPLC. Polyphenol oxidase (PPO) activity was determined by PPO reagent kits, and pH was determined with a pH measuring instrument, etc. The experimental results showed that 1-galloyl-glucose was the smoothest at 5°C among the three storage temperature conditions. It fluctuates and decreases in a curve at 35°C and 25°C. The content changes of gallic acid (GA) fluctuated more obviously at 35°C, and it showed a maximum value on the 7th day. The content changes of 1,3,6-tri-O-galloyl-β-D-glucose (TGG) all showed a peak on the 5th day and then showed a gradual decrease. The content changes of ellagic acid (EA) fluctuated more at 35°C. The peak of the content of rutin at both 35°C and 25°C appeared on the 3rd day, and that showed a gradually decreasing trend. The PPO activity varied more significantly at 25°C and 35°C. The browning index increased with time at both 35°C and 25°C. The complete browning of P. emblica was already observed on the 13th day. Tips for experimental results 5°C are effective in preventing browning of P. emblica. The contents of TGG, 1-galloyl-glucose, and rutin in P. emblica are greatly affected by temperature and time, and its contents had a linear relationship with time and temperature and can be used as one of the indicators of early browning, which provides a reference for the storage and transportation of fresh fruit in Chinese herbals.

Comparative chloroplast genome and transcriptome analysis on the ancient genus Isoetes from China

Isoetes is a famous living fossil that plays a significant role in the evolutionary studies of the plant kingdom. To explore the adaptive evolution of the ancient genus Isoetes from China, we focused on Isoetes yunguiensis (Q.F. Wang and W.C. Taylor), I. shangrilaensis (X. Li, Y.Q. Huang, X.K. Dai & X. Liu), I. taiwanensis (DeVol), I. sinensis (T.C. Palmer), I. hypsophila_GHC (Handel-Mazzetti), and I. hypsophila_HZS in this study. We sequenced, assembled, and annotated six individuals' chloroplast genomes and transcriptomes, and performed a series of analyses to investigate their chloroplast genome structures, RNA editing events, and adaptive evolution. The six chloroplast genomes of Isoetes exhibited a typical quadripartite structure with conserved genome sequence and structure. Comparative analyses of Isoetes species demonstrated that the gene organization, genome size, and GC contents of the chloroplast genome are highly conserved across the genus. Besides, our positive selection analyses suggested that one positively selected gene was statistically supported in Isoetes chloroplast genomes using the likelihood ratio test (LRT) based on branch-site models. Moreover, we detected positive selection signals using transcriptome data, suggesting that nuclear-encoded genes involved in the adaption of Isoetes species to the extreme environment of the Qinghai-Tibetan Plateau (QTP). In addition, we identified 291-579 RNA editing sites in the chloroplast genomes of six Isoetes based on transcriptome data, well above the average of angiosperms. RNA editing in protein-coding transcripts results from amino acid changes to increase their hydrophobicity and conservation in Isoetes, which may help proteins form functional three-dimensional structure. Overall, the results of this study provide comprehensive transcriptome and chloroplast genome resources and contribute to a better understanding of adaptive evolutionary and molecular biology in Isoetes.

High genetic diversity and low population differentiation of a medical plant Ficus hirta Vahl., uncovered by microsatellite loci: implications for conservation and breeding

BACKGROUND

Wuzhimaotao (Radix Fici Hirtae) originates from the dry root of Ficus hirta (Moraceae), which is widely known as a medical and edible plant distributed in South China. As the increasing demand for Wuzhimaotao, the wild F. hirta has been extremely reduced during the past years. It is urgent to protect and rationally develop the wild resources of F. hirta for its sustainable utilization. However, a lack of genetic background of F. hirta makes it difficult to plan conservation and breeding strategies for this medical plant. In the present study, a total of 414 accessions of F. hirta from 7 provinces in southern China were evaluated for the population genetics using 9 polymorphic SSR markers.

RESULTS

A mean of 17.1 alleles per locus was observed. The expected heterozygosity (He) varied from 0.142 to 0.861 (mean = 0.706) in nine SSR loci. High genetic diversity (H_e = 0.706, ranged from 0.613 to 0.755) and low genetic differentiation among populations (G'_ST = 0.147) were revealed at population level. In addition, analysis of molecular variance (AMOVA) indicated that the principal molecular variance existed within populations (96.2%) was significantly higher than that among populations (3.8%). Meanwhile, the three kinds of clustering methods analysis (STRUCTURE, PCoA and UPGMA) suggested that the sampled populations were clustered into two main genetic groups (K = 2). Mantel test showed a significant correlation between geographic and genetic distance among populations (R² = 0.281, P < 0.001). Pollen flow, seed flow and/or geographical barriers might be the main factors that formed the current genetic patterns of F. hirta populations.

CONCLUSIONS

This is a comprehensive study of genetic diversity and population structure of F. hirta in southern China. We revealed the high genetic diversity and low population differentiation in this medicinal plant and clarified the causes of its current genetic patterns. Our study will provide novel insights into the exploitation and conservation strategies for F. hirta.

Genetic diversity and structure of Rhododendron meddianum, a plant species with extremely small populations

Rhododendron meddianum is a critically endangered species with important ornamental value and is also a plant species with extremely small populations. In this study, we used double digest restriction-site-associated DNA sequencing (ddRAD) technology to assess the genetic diversity, genetic structure and demographic history of the three extant populations of R. meddianum. Analysis of SNPs indicated that R. meddianum populations have a high genetic diversity (π = 0.0772 ± 0.0024, H _E  = 0.0742 ± 0.002). Both F _ST values (0.1582-0.2388) and AMOVA showed a moderate genetic differentiation among the R. meddianum populations. Meanwhile, STRUCTURE, PCoA and NJ trees indicated that the R. meddianum samples were clustered into three distinct genetic groups. Using the stairway plot, we found that R. meddianum underwent a population bottleneck about 70,000 years ago. Furthermore, demographic models of R. meddianum and its relative, Rhododendron cyanocarpum, revealed that these species diverged about 3.05 (2.21-5.03) million years ago. This divergence may have been caused by environmental changes that occurred after the late Pliocene, e.g., the Asian winter monsoon intensified, leading to a drier climate. Based on these findings, we recommend that R. meddianum be conserved through in situ, ex situ approaches and that its seeds be collected for germplasm.