Deciphering the effects of genotype and climatic factors on the performance, active ingredients and rhizosphere soil properties of Salvia miltiorrhiza.

Introduction: Salvia miltiorrhiza Bunge is an important medicinal herb, which is widely cultivated in most parts of China. It has attracted considerable attention because of its pharmacological properties and potential health benefits. Methods: We used a field experiment to determine the effects of different genotypes and climatic factors on the performance (plant biomass, morphological parameters), active ingredients, rhizosphere soil physicochemical properties and microbial composition of S. miltiorrhiza at five cultivation locations. Results: The results showed that these parameters were significantly different in the six different genotypes of S. miltiorrhiza from five producing areas. Genotype and soil physicochemical properties were the main factors affecting the growth traits of S. miltiorrhiza, while genotype, climate and soil physicochemical properties were the main factors affecting the content of active components of S. miltiorrhiza. Microbial phospholipid fatty acid analysis showed that the biomass of Gram-positive and Gram-negative bacteria was affected by the genotypes of S. miltiorrhiza plants, while the biomass of arbuscular mycorrhizal fungi, fungi, Gram-positive and Gram-negative bacteria was affected by climate factors. Discussion: Based on the main results, DS993 was the most suitable genotype for S. miltiorrhiza in the five producing areas from the perspective of comprehensive growth traits and medicinal components, while DS993 and DS2000 were suitable for planting in Shandong province from the perspective of origin. DS996 is not suitable for all of the above production areas. These results are helpful to understand the ecological adaptability of different genotypes of S. miltiorrhiza resources, and to select appropriate S. miltiorrhiza genotypes for specific planting areas, so as to maximize yield and quality.

Untargeted Metabolomics Analysis Revealed the Major Metabolites in the Seeds of four Polygonatum Species.

Most Polygonatum species are widely used in China as a source of medicine and food. In this study, a UPLC-QTOF-MS/MS system was used to conduct an untargeted metabolomics analysis and compare the classes and relative contents of metabolites in the seeds of four Polygonatum species: P. sibiricum (Ps), P. cyrtonema (Pc), P. kingianum (Pk), and P. macropodium (Pm). The objectives of this study were to clarify the metabolic profiles of these seeds and to verify their medicinal and nutritional value via comparative analyses. A total of 873 metabolites were identified, including 185 flavonoids, 127 lipids, 105 phenolic acids, and 36 steroids. The comparative analysis of metabolites among Polygonatum seed samples indicated that flavonoids, steroids, and terpenoids were the main differentially abundant compounds. The results of principal component analysis and hierarchical clustering were consistent indicating that the metabolites in Ps and Pm are similar, but differ greatly from Pc and Pk. The data generated in this study provide additional evidence of the utility of Polygonatum seeds for producing food and medicine.

Transcriptome profiles revealed molecular mechanisms of alternating temperatures in breaking the epicotyl morphophysiological dormancy of Polygonatum sibiricum seeds.

BACKGROUND: To adapt seasonal climate changes under natural environments, Polygonatum sibiricum seeds have a long period of epicotyl morphophysiological dormancy, which limits their wide-utilization in the large-scale plant progeny propagation. It has been proven that the controlled consecutive warm and cold temperature treatments can effectively break and shorten this seed dormancy status to promote its successful underdeveloped embryo growth, radicle emergence and shoot emergence. To uncover the molecular basis of seed dormancy release and seedling establishment, a SMRT full-length sequencing analysis and an Illumina sequencing-based comparison of P. sibiricum seed transcriptomes were combined to investigate transcriptional changes during warm and cold stratifications. RESULTS: A total of 87,251 unigenes, including 46,255 complete sequences, were obtained and 77,148 unigenes (88.42%) were annotated. Gene expression analyses at four stratification stages identified a total of 27,059 DEGs in six pairwise comparisons and revealed that more differentially expressed genes were altered at the Corm stage than at the other stages, especially Str_S and Eme. The expression of 475 hormone metabolism genes and 510 hormone signaling genes was modulated during P. sibiricum seed dormancy release and seedling emergence. One thousand eighteen transcription factors and five hundred nineteen transcription regulators were detected differentially expressed during stratification and germination especially at Corm and Str_S stages. Of 1246 seed dormancy/germination known DEGs, 378, 790, and 199 DEGs were associated with P. sibiricum MD release (Corm vs Seed), epicotyl dormancy release (Str_S vs Corm), and the seedling establishment after the MPD release (Eme vs Str_S). CONCLUSIONS: A comparison with dormancy- and germination-related genes in Arabidopsis thaliana seeds revealed that genes related to multiple plant hormones, chromatin modifiers and remodelers, DNA methylation, mRNA degradation, endosperm weakening, and cell wall structures coordinately mediate P. sibiricum seed germination, epicotyl dormancy release, and seedling establishment. These results provided the first insights into molecular regulation of P. sibiricum seed epicotyl morphophysiological dormancy release and seedling emergence. They may form the foundation of future studies regarding gene interaction and the specific roles of individual tissues (endosperm, newly-formed corm) in P. sibiricum bulk seed dormancy.

Comparative transcriptomic analysis reveals genes regulating the germination of morphophysiologically dormant Paris polyphylla seeds during a warm stratification.

We previously analyzed the expression of genes associated with Paris polyphylla var. yunnanensis seed maturation and dormancy release; however, we were unable to clarify the relationship between gene expression levels and these processes. To reveal the molecular mechanisms underlying P. polyphylla var. yunnanensis seed dormancy release during a warm stratification, the transcriptomes of dormant and germinating P. polyphylla var. yunnanensis seeds were separately analyzed by RNA sequencing and were also compared with the transcriptomes of stem-leaf and root tissues harvested during the seed maturation stage. The RNA sequencing of five tissues generated 234,331 unigenes, of which 10,137 (4.33%) were differentially expressed among the analyzed tissues. The 6,619 unigenes whose expression varied among mature dormant, sprouted, and germinated seeds included 95 metabolic and 62 signaling genes related to abscisic acid, gibberellin, auxin, brassinosteroid, cytokinin, ethylene, jasmonic acid and salicylic acid. Additionally, 243 differentially expressed genes were annotated as known seed dormancy/germination-related genes. Among these genes, 109 were regulated by hormones or involved in hormone signal transduction. Finally, 310 transcription factor unigenes, including 71 homologs of known seed dormancy/ germination-related genes, were observed to be differentially expressed during a warm stratification. These results confirm that multiple hormones and transcription factors influence P. polyphylla var. yunnanensis seed dormancy release and germination during a warm stratification. This study identified candidate genes (e.g., ABI5) that should be cloned and functionally characterized regarding their effects on the release of P. polyphylla var. yunnanensis seed morphophysiological dormancy.

Quality evaluation of Panax quinquefolium from different cultivation regions based on their ginsenoside content and radioprotective effects on irradiated mice.

Ginsenosides are one of major types of bioactive compounds in American ginseng (AG) and utilized to assess the quality of various AG samples. The contents of ginsenosides showed cultivation region-related variation, which is possibly associated with AG's pharmacological effect difference. Therefore, to reveal the quality difference of AGs in different cultivation regions, AG samples from seven cultivation regions were evaluated via analyzing their contents of nine ginsenosides and the biochemical parameters in AG-treated irradiated mice. Pre-administration of AG decoctions could reversely modulate the irradiation-induced changes of antioxidant enzymatic activity, cytokine level and hormone level in irradiated mice, which demonstrated that AG had the radioprotective effects due to its antioxidative, immunomodulatory and anti-inflammatory properties. However, this radioprotection effect varied among different cultivation regions of AGs. Collectively, Beijing and Canada-cultivated AGs had the best radioprotection. Heilongjiang and Jilin-originated AGs had the similar pharmacological effects while USA, Shandong and Shaanxi-grown AGs had closer pharmacological effects. This biochemical measurements-based PCA and heatmap clustering of AGs from seven cultivation regions was nearly consistent with ginsencoside content- and the previous serum metabolome-based analyses. However, the pearson correlation analysis revealed that only Rb3 and Rd were significantly correlated with some of assayed biochemical parameters in irradiated mice pretreated with different cultivation regions of AG extracts.

A Widely Metabolomic Analysis Revealed Metabolic Alterations of Epimedium Pubescens Leaves at Different Growth Stages.

Epimedium folium is the major medicinally-used organ of Epimedium species and its metabolic changes during the leaf growth have not been studied at the metabolomic level. E. pubescens is one of five recorded species in the Pharmacopoeia of the People's Republic of China and widely grows in China. A UPLC-ESI-MS/MS-based targeted metabolomic analysis was implemented to explore the metabolite composition in E. pubescens leaves under the cultivation condition and further to investigate their temporal variations among four representative growth stages. A total of 403 metabolites, including 32 hitherto known in Epimedium species, were identified in E. pubescens leaf, of which 302 metabolites showed the growth/development-dependent alterations. Flavonoid-type compounds were the major composition of the metabolites identified in this study. Most flavonoids, together with tannin-type and lignans and coumarin-type compounds, were up-regulated with E. pubescens leaf growth and maturation after the full flowering stage. Our results not only greatly enriched the existing Epimedium phytochemical composition database and also, for the first time, provided the metabolomics-wide information on metabolic changes during E. pubescens leaf growth and development, which would facilitate in the choice of an optimum harvest time to balance a higher biomass yield of Epimedium folium with its better medicinal quality.

UPLC-Q/TOF-MS-Based Serum Metabolomics Reveals Hypoglycemic Effects of Rehmannia glutinosa, Coptis chinensis and Their Combination on High-Fat-Diet-Induced Diabetes in KK-Ay Mice.

Diabetes is a worldwide severe health issue which causes various complications. This study aimed to evaluate the hypoglycemic effects of Rehmannia glutinosa (RG), Coptis chinensis (CC) alone and their combination on high-fat-diet-induced diabetes in mice via biochemical assays and UPLC-Q/TOF-MS-based serum metabolomic analysis. Diabetic KK-Ay mice were induced by high-fat diet and treated for eight weeks, separately with RG, CC and their combination and the positive control drug metformin. Administration of RG and CC alone, and their combination could decrease the fasting blood glucose level, ameliorate the tolerance of glucose, and recover the levels of total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C) in sera of diabetic mice. Orthogonal partial least squares discriminant analysis (OPLS-DA) on serum metabolomes revealed that 79 ESI⁺ and 76 ESI- metabolites were changed by diabetes mellitus (DM) compared to the normal control. Heatmaps on these diabetes-related metabolites showed that CC and RG/CC were clustered closer with the normal control, indicating that they had the better antidiabetic effects at the metabolite level. Fifteen of the differential metabolites in DM serum were annotated and their related metabolic pathways were lipid metabolism. These data suggested that RG and CC alone and in combination treatment had the antidiabetic activity in lowering glycemia and improving lipid metabolism. UPLC-Q/TOF-MS-based metabolomics shed light on the differential metabolite effects of RG and CC in DM treatment. However, it should be noted that some differential metabolites were possibly generated or not detected due to our groupwise run order, which possibly contributed to or covered the group difference in our experiment. They need to be further discriminated in the future work.

Comparison of Serum Metabolite Changes of Radiated Mice Administered with Panax quinquefolium from Different Cultivation Regions Using UPLC-Q/TOF-MS Based Metabolomic Approach.

Chemometric analysis of bioactive compounds revealed that American ginsengs (AGs) from different cultivation regions of China had a difference in quality, which indicates their possible pharmacological difference. A UPLC-Q/TOF-MS-based untargeted metabolomic approach was used to uncover serum metabolite changes in radiated mice pre-administered with AG root decoctions from seven cultivation regions and to further assess their quality difference. OPLS-DA revealed that 51 metabolites (ESI−) and 110 (ESI⁺) were differentially expressed in sera between the control and the radiated model mice. Heatmap analysis further revealed that AG could not reverse most of these radiation-altered metabolites, which indicates dietary supplement of AG before cobalt radiation had the weak potential to mediate serum metabolites that were altered by the sub-lethal high dose radiation. In addition, 83 (ESI−) and 244 (ESI⁺) AG altered metabolites were detected in radiated mice under radiation exposure. Both OPLS-DA on serum metabolomes and heatmap analysis on discriminant metabolites showed that AGs from different cultivation regions differentially influenced metabolic alterations in radiated mice, which indicates AGs from different cultivation regions showed the pharmacological difference in modulation of metabolite changes. AGs from Shandong, Shanxi, and Beijing provinces had more similar pharmacological effects than AGs from USA, Canada, Jilin, and Heilongjiang. Finally, 28 important potential biomarkers were annotated and assigned onto three metabolic pathways including lipid, amino acid, and energy metabolisms.

Simultaneous Determination of Catalpol, Aucubin, and Geniposidic Acid in Different Developmental Stages of Rehmannia glutinosa Leaves by High Performance Liquid Chromatography.

Although R. glutinosa roots are currently the only organ source in clinics, its leaves are a potential supplement for the roots especially in extraction of some important bioactive compounds. Our early work found that the contents of catalpol and total iridoid glycosides varied among different developmental stages of R. glutinosa leaves. Aucubin and geniposidic acid, the abundant major bioactive compounds in Eucommia ulmoides and Gardenia jasminoides, respectively, were found present in R. glutinosa roots, however, and have not been analyzed in its leaves. In this paper, we aimed to determine contents of these three iridoid glycosides in different developmental stages of R. glutinosa leaves using the optimized HPLC-UV conditions. Our results showed that aucubin and GPA in R. glutinosa leaves were much lower than catalpol and showed the increasing trend with the leaf development, which was different from catalpol. This work provided the important information for future exploitation of R. glutinosa leaves as a potential supplement for its roots in extraction of some important bioactive compounds and studying the relationship of aucubin and catalpol metabolism.

Determination of Saponin Content in Hang Maidong and Chuan Maidong via HPLC-ELSD Analysis.

Zhejiang and Sichuan are regarded as two genuine producing areas of Ophiopogonis radix in China. To study the difference in the quality of Ophiopogonis radix from these two places, the contents of three reported bioactive saponins, that is, ophiopogonins B, D, and D', in tubers and fibrous roots of Ophiopogon japonicus from Cixi city of Zhejiang and Santai county of Sichuan were quantified using HPLC-ELSD method and compared. Ophiopogonin B and ophiopogonin D' content in tubers of HMD were higher than those in radix of CMD, whereas ophiopogonin D in HMD was about twice lower than that of CMD. Three ophiopogonins were all detected in fibrous roots of both HMD and CMD. Their averaged content in fibrous roots of CMD was about twice higher than that in tubers of CMD. Ophiopogonin D in fibrous roots of CMD was about five times higher than that of HMD. Our biochemical assay revealed that fibrous roots and tubers of CMD can be of an important saponin source, especially for ophiopogonin D.

Identification and developmental expression profiling of putative alkaloid biosynthetic genes in Corydalis yanhusuo bulbs.

Alkaloids in bulbs of Corydalis (C.) yanhusuo are the major pharmacologically active compounds in treatment of blood vessel diseases, tumors and various pains. However, due to the absence of gene sequences in C. yanhusuo, the genes involved in alkaloid biosynthesis and their expression during bulb development remain unknown. We therefore established the first transcriptome database of C. yanhusuo via Illumina mRNA-Sequencing of a RNA composite sample collected at Bulb initiation (Day 0), early enlargement (Day 10) and maturation (Day 30). 25,013,630 clean 90 bp paired-end reads were de novo assembled into 47,081 unigenes with an average length of 489 bp, among which 30,868 unigenes (65.56%) were annotated in four protein databases. Of 526 putative unigenes involved in biosynthesis o f various alkaloids, 187 were identified as the candidate genes involved in the biosynthesis of benzylisoquinoline alkaloids (BIAs), the only alkaloid type reported in C. yanhusuo untill now. BIAs biosynthetic genes were highly upregulated in the overall pathway during bulb development. Identification of alkaloid biosynthetic genes in C. yanhusuo provide insights on pathways and molecular regulation of alkaloid biosynthesis, to initiate metabolic engineering in order to improve the yield of interesting alkaloids and to identify potentially new alkaloids predicted from the transcriptomic information.

Dynamic transcriptional profiling provides insights into tuberous root development in Rehmannia glutinosa.

Rehmannia glutinosa, an herb of the Scrophulariaceae family, is widely cultivated in the Northern part of China. The tuberous root has well-known medicinal properties; however, yield and quality are threatened by abiotic and biotic stresses. Understanding the molecular process of tuberous root development may help identify novel targets for its control. In the present study, we used Illumina sequencing and de novo assembly strategies to obtain a reference transcriptome that is relevant to tuberous root development. We then conducted RNA-seq quantification analysis to determine gene expression profiles of the adventitious root (AR), thickening adventitious root (TAR), and the developing tuberous root (DTR). Expression profiling identified a total of 6794 differentially expressed unigenes during root development. Bioinformatics analysis and gene expression profiling revealed changes in phenylpropanoid biosynthesis, starch and sucrose metabolism, and plant hormone biosynthesis during root development. Moreover, we identified and allocated putative functions to the genes involved in tuberous root development, including genes related to major carbohydrate metabolism, hormone metabolism, and transcription regulation. The present study provides the initial description of gene expression profiles of AR, TAR, and DTR, which facilitates identification of genes of interest. Moreover, our work provides insights into the molecular mechanisms underlying tuberous root development and may assist in the design and development of improved breeding schemes for different R. glutinosa varieties through genetic manipulation.

Transcriptomic analysis of American ginseng seeds during the dormancy release process by RNA-Seq.

American ginseng (Panax quinquefolius L.) is an important herb that is cultivated in China, North American, and South Korea. It is propagated from seed, but the seed has deep dormancy characteristics described as morphophysiological dormancy. Two-stage temperature stratification, a warm (15-20°C) and cold (2°C) stratification period of 6 months, has been used successfully for seed dormancy release. However, little is known about the molecular mechanisms of seed dormancy release in the stratification process. In this study, seed development after pollination and seed development in the dormancy release process were investigated in American ginseng. The transcriptome during seed dormancy release was analyzed using RNA-Seq technology and 78,207 unigenes (mean length 531 bp) were generated. Based on similarity searches of public databases, 54,292 of the unigenes (69.4%) were functionally annotated. Further, three digital gene expression (DGE) libraries were sequenced and differences in gene expression at three stages during seed cold stratification were examined. The greatest number of differentially expressed genes occurred in the 90DCS versus 180DCS libraries, while the lowest number of differentially expressed genes occurred in the 135DCS verus 180DCS libraries. GO enrichment analysis revealed that 59, 29, and 39 GO terms were significantly enriched in the biological process, molecular function, and cell component GO categories, respectively. There were 25,190 genes with KEGG pathway annotation in the three DGE libraries and their enrichment pathways were compared. The gene expressions of 30 selected unigenes were validated using quantitative PCR. This study is the first to provide the transcriptome sequences for seed dormancy release in American ginseng, and demonstrates the successful use of DGE profiling data for analyzing transcriptomic variation during dormancy release. These data provide a basis for future researches of seed dormancy in morphophysiological dormancy seeds in non-model plants.

[Study on distribution and dynamic accumulation of catalpol and total iridoid in fresh Rehmannia glutinosa].

Iridoid glycosides were the main active ingredient of Rehmannia glutinosa, of which catalpol has the highest content. This work will provide theoretical basis for metabolic study and cultivation of iridoids on the basis of the dynamic accumulation of catalpol and total iridoids in the growth of R. glutinosa. The samples of rehmannia 85-5 were gathered in the same filed from July to October. The contents of catalpol and total iridoid glycosides were measured by HPLC and specteophotometric, respectively. The results showed that youngest leaves had the higher content of catalpol and total iridoid glyosides than that of the other two leaf ages in the same growth stage from July to September, while their content of catalpol and total iridoid glycosides were all decreased as the growth of leaves of R. glutinosa. The content of catalpol didn't differ significantly from July to September, whereas it has significantly increased in October in the three leaf stage. In the same stage, the wider the root diameter is, the higher content of the effective components are. In August and September, the total iridoid glycosides have the fastest accumulation. The content of catalpol was increased as the accumulation of total iridoid glycosides.

Transcriptome Profiling Identifies Candidate Genes Associated with the Accumulation of Distinct Sulfur γ-Glutamyl Dipeptides in Phaseolus vulgaris and Vigna mungo Seeds.

Common bean (Phaseolus vulgaris) and black gram (Vigna mungo) accumulate γ-Glutamyl-S-methylcysteine and γ-Glutamyl-methionine in seed, respectively. Transcripts were profiled by 454 pyrosequencing data at a similar developmental stage coinciding with the beginning of the accumulation of these metabolites. Expressed sequence tags were assembled into Unigenes, which were assigned to specific genes in the early release chromosomal assembly of the P. vulgaris genome. Genes involved in multiple sulfur metabolic processes were expressed in both species. Expression of Sultr3 members was predominant in P. vulgaris, whereas expression of Sultr5 members predominated in V. mungo. Expression of the cytosolic SERAT1;1 and -1;2 was approximately fourfold higher in P. vulgaris while expression of the plastidic SERAT2;1 was twofold higher in V. mungo. Among BSAS family members, BSAS4;1, encoding a cytosolic cysteine desulfhydrase, and BSAS1;1, encoding a cytosolic O-acetylserine sulphydrylase were most highly expressed in both species. This was followed by BSAS3;1 encoding a plastidic ß-cyanoalanine synthase which was more highly expressed by 10-fold in P. vulgaris. The data identify BSAS3;1 as a candidate enzyme for the biosynthesis of S-methylcysteine through the use of methanethiol as substrate instead of cyanide. Expression of GLC1 would provide a complete sequence leading to the biosynthesis of γ-Glutamyl-S-methylcysteine in plastids. The detection of S-methylhomoglutathione in P. vulgaris suggested that homoglutathione synthetase may accept, to some extent, γ-Glutamyl-S-methylcysteine as substrate, which might lead to the formation of S-methylated phytochelatins. In conclusion, 454 sequencing was effective at revealing differences in the expression of sulfur metabolic genes, providing information on candidate genes for the biosynthesis of distinct sulfur amino acid γ-Glutamyl dipeptides between P. vulgaris and V. mungo.

Transcripts of sulphur metabolic genes are co-ordinately regulated in developing seeds of common bean lacking phaseolin and major lectins.

The lack of phaseolin and phytohaemagglutinin in common bean (dry bean, Phaseolus vulgaris) is associated with an increase in total cysteine and methionine concentrations by 70% and 10%, respectively, mainly at the expense of an abundant non-protein amino acid, S-methyl-cysteine. Transcripts were profiled between two genetically related lines differing for this trait at four stages of seed development using a high density microarray designed for common bean. Transcripts of multiple sulphur-rich proteins were elevated, several previously identified by proteomics, including legumin, basic 7S globulin, albumin-2, defensin, albumin-1, the Bowman-Birk type proteinase inhibitor, the double-headed trypsin inhibitor, and the Kunitz trypsin inhibitor. A co-ordinated regulation of transcripts coding for sulphate transporters, sulphate assimilatory enzymes, serine acetyltransferases, cystathionine ß-lyase, homocysteine S-methyltransferase and methionine gamma-lyase was associated with changes in cysteine and methionine concentrations. Differential gene expression of sulphur-rich proteins preceded that of sulphur metabolic enzymes, suggesting a regulation by demand from the protein sink. Up-regulation of SERAT1;1 and -1;2 expression revealed an activation of cytosolic O-acetylserine biosynthesis. Down-regulation of SERAT2;1 suggested that cysteine and S-methyl-cysteine biosynthesis may be spatially separated in different subcellular compartments. Analysis of free amino acid profiles indicated that enhanced cysteine biosynthesis was correlated with a depletion of O-acetylserine. These results contribute to our understanding of the regulation of sulphur metabolism in developing seed in response to a change in the composition of endogenous proteins.

Genetic structure and phylogeography of rice landraces in Yunnan, China, revealed by SSR.

Yunnan Province is one of the largest centers of genetic diversity of Oryza sativa L. in China, and in the world. Using a genetically representative core collection of 692 rice landraces from Yunnan, the genetic structure, differentiation, and geographic diversity of this rice germplasm were analyzed. The accessions were classified into different populations, according to the model-based structure analysis. Model-based populations were characterized through the reconstruction of a neighbor-joining tree, principal coordinate analysis, and the estimation of morphologic and SSR variations. Finally, the distribution of genetic diversity and differentiation among districts were studied. Seven model-based populations were identified on the basis of the structure analysis. This classification was partly consistent with Ting's 5-level taxonomic system. Differentiation between 2 rice subspecies is the most apparent, with a clearer differentiation between soil-watery ecotypes in japonica than in indica; however, differentiation among seasonal ecotypes in indica is clearer than in japonica. Cropping system and man-made restricted-growth environments could be considered to be the main forces driving the intraspecific differentiation of cultivated rice. It has been suggested that, because it possesses the highest genetic diversity and all the necessary conditions as a center of genetic diversity, the southwest region of Yunnan, encompassing Simao, Lincang, and Xishuangbanna districts, is the center of genetic diversity of Yunnan rice landraces.