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Abstract Notoginseng saponin R1; ginsenosides Rg1, Re, Rb1, and Rd; the sum of the five saponins; and underground-part fresh weight (UPFW) of single plants were used as quality evaluation indices for Panax notoginseng (Burk.) F. H. Chen (P. notoginseng). Comprehensive evaluation of P. notoginseng samples from 30 production areas was performed using that MaxEnt model. Spatial pattern changes in suitable P. notoginseng habitats were predicted for current and future periods (2050s, 2070s, and 2090s) using SSP126 and SSP585 models. The results revealed that temperature, precipitation, and solar radiation were important environmental variables. Suitable habitats were located mainly in Yunnan, Guizhou, and Sichuan Provinces. The distribution core of P. notoginseng is predicted to shift southeast in the future. The saponin content decreased from the southeast to the northwest of Yunnan Province, which was contrary to the UPFW trend. This study provides the necessary information for the protection and sustainable utilization of P. notoginseng resources, and a theoretical reference for its application in the quality evaluation of Chinese medicinal products.

Notoginseng saponin R1; ginsenosides Rg1, Re, Rb1, and Rd; the sum of the five saponins; and underground-part fresh weight (UPFW) of single plants were used as quality evaluation indices for Panax notoginseng (Burk.) F. H. Chen (P. notoginseng). Comprehensive evaluation of P. notoginseng samples from 30 production areas was performed using that MaxEnt model. Spatial pattern changes in suitable P. notoginseng habitats were predicted for current and future periods (2050s, 2070s, and 2090s) using SSP126 and SSP585 models. The results revealed that temperature, precipitation, and solar radiation were important environmental variables. Suitable habitats were located mainly in Yunnan, Guizhou, and Sichuan Provinces. The distribution core of P. notoginseng is predicted to shift southeast in the future. The saponin content decreased from the southeast to the northwest of Yunnan Province, which was contrary to the UPFW trend. This study provides the necessary information for the protection and sustainable utilization of P. notoginseng resources, and a theoretical reference for its application in the quality evaluation of Chinese medicinal products. [ABSTRACT FROM AUTHOR]

Panax notoginseng (Burk.) F. H. Chen, a species of the genus Panax, radix has been traditionally used to deal with various hematological diseases and cardiovascular diseases since ancient times in East Asia. P. notoginseng produces recalcitrant seeds which are sensitive to desiccation and difficult to store for a long time. However, few data are available on the mechanism of the desiccation sensitivity of P. notoginseng seeds. To gain a comprehensive perspective of the genes associated with desiccation sensitivity, cDNA libraries from seeds under control and desiccation processes were prepared independently for Illumina sequencing. The data generated a total of 70,189,896 reads that were integrated and assembled into 55,097 unigenes with a mean length of 783 bp. In total, 12,025 differentially expressed genes (DEGs) were identified during the desiccation process. Among these DEGs, a number of central metabolism, hormonal network-, fatty acid-, and ascorbate-glutathione-related genes were included. Our data provide a comprehensive resource for identifying the genes associated with the desiccation sensitivity of P. notoginseng seeds. [ABSTRACT FROM AUTHOR]

The fungal community structure and soil fertility in rhizosphere soil have an important effect on the health of Panax notoginseng (P. notoginseng). The attack of pathogenic fungi and the imbalance of soil fertility can easily lead to diseases. The effect of Bacillus subtilis on improving the community structure of soil fungi has been confirmed, and the corresponding biological agent products have been commercialized. A pot experiment carried out in a greenhouse explored the effect of a biological agent and fertilizer on the fungal community in the rhizosphere of P. notoginseng. In the experiment, fertilization and the addition of biological agents were set up with three gradients, respectively, and the full coupling experiment was adopted, and the blank control group (CK) was set up at the same time. Therefore, there were thirteen treatments in the experiment. NH4 decreased between 36.42% and 11.56%, AP increased between 6.03% and 92.46%, AK increased between 2.99% and 25.40%, TN increased between 0.10% and 9.41%, and TP increased by 18.25% to 47.73% The addition of Bacillus subtilis biological agent decreased the Chao1, Shannon, Simpson, and ACE index of fungi in the rhizosphere soil of P. notoginseng. The Chao1 index decreased between 0.39% and 78.22%; the ACE index decreased between 0.43% and 78.24%. The main pathogenic fungi Cylindrocarpon and Fusarium of P. notoginseng were different in the experimental results. Cylindrocarpon decreased under F1C1, F2C1, and F3C2 treatments, while Fusarium increased under F1C1, F2C2, F3C1, and F3C3 treatments and decreased Fusarium content in rhizosphere soil of P. notoginseng in other treatments. RDA analysis (Redundancy analysis) showed that NH4-N was negatively correlated with the main pathogen Cylindrocarpon, Fusarium, and Ilyonectria, while AP and AK were positively correlated with Cylindrocarpon, Fusarium, and Ilyonectria. The results of the GRA-TOPSIS analysis showed that the score of F3C2 was the highest, while F2C3 and F2C1 ranked second and third, respectively. The calculation results of the theoretical model based on GRA-TOPSIS analysis showed that the GRA-TOPSIS score was highest when the theoretical optimal fertilizer application rate and bacteria application rate were 116.31 kg hm−2 and 15.83 kg hm−2, respectively. [ABSTRACT FROM AUTHOR]

Purpose: This work integrated field investigation results with laboratory experiments to investigate the interaction of rhizosphere soil microorganisms in the continuous cropping of Panax notoginseng and saponins, providing a scientific foundation for overcoming P. notoginseng continuous cropping obstacles. Methods: The concentrations of saponins were measured using UPLC–MS/MS, and the microbes in the P. notoginseng rhizosphere soil were sequenced using the Illumina MiSeq high-throughput platform. Results: The concentrations of ginsenoside Rd, ginsenoside Rg2, ginsenoside Rg1, ginsenoside Re, ginsenoside Rb1 and notoginsenoside R1 in the rhizospheric soil of infected P. notoginseng increased considerably. The P. notoginseng rhizospheric soil rapidly degraded saponins in the following order: ginsenoside Rd > ginsenoside Rg1 > notoginsenoside R1 > ginsenoside Re > ginsenoside Rg2 > ginsenoside Rb1. Saponins substantially enhanced the fungal Chao1 index, and Rd had the greatest effect. Saponins shifted the microbial community architecture and abundance in the rhizosphere soil. Ginsenoside Re stimulated the growth of Rhodotorula and Alternaria, ginsenoside Rg1 significantly increased the production of Spizellomyces, ginsenoside Rd promoted the proliferation of Aureobasidium, and notoginsenoside R1 fostered the growth of Alternaria. Further investigations showed that increases in Plectosphaerella and Clonostachys were directly and positively related to notoginsenoside R1, ginsenoside Rg1, and ginsenoside Rb1, while an increase in Ilyonectria was strongly and positively related to ginsenoside Rb1 and ginsenoside Rg2. Conclusions: The six saponins have the potential to shape the structure of the microbial community of the P. notoginseng rhizospheric soil, and enrichment in particular saponins lays the foundation for the emergence and proliferation of pathogenic fungi. [ABSTRACT FROM AUTHOR]

Panax notoginseng (Burk.) F. H. Chen, a species of the genus Panax, radix has been traditionally used to deal with various hematological diseases and cardiovascular diseases since ancient times in East Asia. P. notoginseng produces recalcitrant seeds which are sensitive to desiccation and difficult to store for a long time. However, few data are available on the mechanism of the desiccation sensitivity of P. notoginseng seeds. To gain a comprehensive perspective of the genes associated with desiccation sensitivity, cDNA libraries from seeds under control and desiccation processes were prepared independently for Illumina sequencing. The data generated a total of 70,189,896 reads that were integrated and assembled into 55,097 unigenes with a mean length of 783 bp. In total, 12,025 differentially expressed genes (DEGs) were identified during the desiccation process. Among these DEGs, a number of central metabolism, hormonal network-, fatty acid-, and ascorbate-glutathione-related genes were included. Our data provide a comprehensive resource for identifying the genes associated with the desiccation sensitivity of P. notoginseng seeds.

Large-scale intensive cultivation has made continuous cropping soil sickness more serious for Panax notoginseng in Yunnan. Autotoxic substances can promote the occurrence of continuous cropping soil sickness. Phenolic acids exert a strong autotoxic effect on P. notoginseng. Based on UPLC-MS/MS, the levels of six phenolic acids with the strongest autotoxicity of P. notoginseng rhizospheric soil were tested. Based on Illumina MiSeq high-throughput sequencing technology, the variation in the microbial diversity in the rhizospheric soil was used as an index to explore the interactions between phenolic acids and the soil microorganisms of the P. notoginseng rhizosphere. (1) Continuous P. notoginseng cropping significantly changed the microbial community structure. Continuous cropping increased bacterial Chao1 index and Shannon index and decreased fungal Shannon index. After P. notoginseng disease, bacterial Shannon index reduced and fungal Chao1 index decreased. (2) Phenolic acid significantly changed the bacterial community structure. VA significantly reduced the bacterial Shannon index. Exogenous p -HA, FA, SA, and VA significantly increased the fungal Chao1 index and p -HA showed the most significant effect. Para-HA affected bacterial specificity, and VA affected fungal specificity. (3) VA was positively correlated with most fungi and bacteria. Para-HA was positively correlated with Lelliottia and Flavobacterium. Para-HA was also positively correlated with plant pathogens (Fusarium and Ilyonectria). Para-HA and VA were able to promote the growth of primary pathogenic bacteria. Thus, p -HA and VA are the main phenolic acid-autotoxin substances in P. notoginseng under continuous cropping. (4) A correlation analysis of soil environmental factors associated with fungal and bacterial communities showed that AK, TN, OM, and HN were most strongly correlated with soil microorganisms. (5) The microorganisms in the rhizosphere of 3-year-old soil planted with P. notoginseng exhibited obvious effects on the degradation of the four phenolic acids. The effect of soil microorganisms on phenolic acids was first-order kinetic degradation with a high degradation rate and a half-life of less than 4.5 h. The results showed that phenolic acids could promote the growth of pathogenic bacteria. And the interaction between rhizospheric soil microorganisms and phenolic acids was the main cause of the disturbance of P. notoginseng rhizosphere microflora. [ABSTRACT FROM AUTHOR]

Ginsenosides are saponins found in plants of panax genus. Despite having a wide range of health benefits, they cannot optimally reach their target tissues and organs due to their low intestinal absorption. However, reduction of their sugar moieties can produce more absorbable and bioactive compounds. Even though they are known as a good source of glycosidase, edible and medicinal mushrooms are less investigated for their capability to hydrolyse ginsenosides. An enzyme from Cordyceps militaris was used to convert ginsenosides from Panax notoginseng roots. Response surface methodology was used to study the effect of temperature (30 – 60 °C), pH (6 – 7), time (30–80 h) and enzyme concentration (0.5 – 1%), on minor ginsenoside production and optimum conditions for maximum ginsenoside hydrolysis. Regression analysis was used to develop a second-degree polynomial model for the production of minor ginsenosides. Statistical significance of the model was evidenced by coefficient of determination (R2 = 95.15%) and (P value = 0.000). Minor ginsenosides production was affected by enzyme concentration, temperature and time respectively in order of magnitude. The effect of pH was found insignificant. Maximal minor ginsenosides were found at 0.86% enzyme concentration, 42.88 °C, 62.63 h and pH 6.62. A significant difference between hydrolysates from different treatments was observed for DPPH scavenging activity and antimicrobial activity. Hydrolysates have shown a strong cytotoxic activity against (SK-LU-1) and (MCF-7) cell lines. The model developed for Panax notoginseng hydrolysis by C. militaris derived glycosidase can potentially be used for producing minor ginsenosides with improved bioactivities for use in the production of food and medicines.

Soil fumigation with chloropicrin (CP) is an effective means of overcoming continuous cropping obstacles (CCO) in Panax notoginseng and improving its yield and quality. CP fumigation can change the microbial community of soil. Therefore, a key step after CP fumigation is the rapid restoration of soil microorganisms and the promotion of beneficial microorganism proliferation as the dominant flora. In this study, continuously cropped soil of P. notoginseng was fumigated with CP, and general organic fertilizer (GOF) or microbial organic fertilizer (MOF) was used to restore soil microorganisms after fumigation. Soil physical and chemical properties, soil microorganisms, and quality of P. notoginseng were investigated. The application of MOF and GOF after CP fumigation promoted increases in soil nitrogen (9.88% and 8.21%, respectively), phosphorus (21.39% and 11.57%, respectively), potassium (7.99% and 2.75%, respectively), and the quality of P. notoginseng; it also promoted the accumulation of saponins in the main roots (23.62% and 9.12%, respectively). Application of MOF and GOF can restore the diversity of microorganisms in the soil. MOF increased the relative abundance of the beneficial soil microorganisms Glomeromycota, Mortierellomycota, Humicola and Bacillus, thereby lowering the relative abundance of the harmful Ascomycota and Fusarium relative to GOF. In summary, CP fumigation reduces the diversity of microorganisms in the soil. The addition of organic fertilizer can promote microbial diversity and increase the relative abundance of beneficial species. Moreover, the promotion effect of MOF is better than that of GOF, thereby improving soil fertility and ultimately promoting the quality and yield of P. notoginseng.

Large-scale intensive cultivation has made continuous cropping soil sickness more serious for Panax notoginseng in Yunnan. Autotoxic substances can promote the occurrence of continuous cropping soil sickness. Phenolic acids exert a strong autotoxic effect on P. notoginseng. Based on UPLC-MS/MS, the levels of six phenolic acids with the strongest autotoxicity of P. notoginseng rhizospheric soil were tested. Based on Illumina MiSeq high-throughput sequencing technology, the variation in the microbial diversity in the rhizospheric soil was used as an index to explore the interactions between phenolic acids and the soil microorganisms of the P. notoginseng rhizosphere. (1) Continuous P. notoginseng cropping significantly changed the microbial community structure. Continuous cropping increased bacterial Chao1 index and Shannon index and decreased fungal Shannon index. After P. notoginseng disease, bacterial Shannon index reduced and fungal Chao1 index decreased. (2) Phenolic acid significantly changed the bacterial community structure. VA significantly reduced the bacterial Shannon index. Exogenous p-HA, FA, SA, and VA significantly increased the fungal Chao1 index and p-HA showed the most significant effect. Para-HA affected bacterial specificity, and VA affected fungal specificity. (3) VA was positively correlated with most fungi and bacteria. Para-HA was positively correlated with Lelliottia and Flavobacterium. Para-HA was also positively correlated with plant pathogens (Fusarium and Ilyonectria). Para-HA and VA were able to promote the growth of primary pathogenic bacteria. Thus, p-HA and VA are the main phenolic acid-autotoxin substances in P. notoginseng under continuous cropping. (4) A correlation analysis of soil environmental factors associated with fungal and bacterial communities showed that AK, TN, OM, and HN were most strongly correlated with soil microorganisms. (5) The microorganisms in the rhizosphere of 3-year-old soil planted with P. notoginseng exhibited obvious effects on the degradation of the four phenolic acids. The effect of soil microorganisms on phenolic acids was first-order kinetic degradation with a high degradation rate and a half-life of less than 4.5 h. The results showed that phenolic acids could promote the growth of pathogenic bacteria. And the interaction between rhizospheric soil microorganisms and phenolic acids was the main cause of the disturbance of P. notoginseng rhizosphere microflora.

Panax notoginseng (Panax notoginseng (Burk.) F.H. Chen), a plant of high medicinal value, is severely affected by root rot during cultivation. Here, we generated a reference genome of P. notoginseng, with a contig N50 size of 241.268 kb, and identified 66 disease-resistance genes (R-genes) as candidate genes for breeding disease-resistant varieties. We then investigated the molecular mechanism underlying the responses of resistant and susceptible P. notoginseng genotypes to Fusarium oxysporum infection at six time points by RNA-seq. Functional analysis of the genes differentially expressed between the two genotypes indicated that genes involved in the defense response biological process like hormone transduction and plant-pathogen interaction are continuously and highly expressed in resistant genotype during infection. Moreover, salicylic acid and jasmonic acid levels gradually increased during infection in the resistant genotype. Coexpression analysis showed that PnWRKY22 acts as a hub gene in the defense response of the resistant genotype. Finally, transiently overexpressing PnWRKY22 increased salicylic acid levels in P. notoginseng leaves. Our findings provide a theoretical basis for studying root rot resistance in P. notoginseng. [ABSTRACT FROM AUTHOR]

Panax notoginseng, a perennial herb of the genus Panax in the family Araliaceae, has played an important role in clinical treatment in China for thousands of years because of its extensive pharmacological effects. Here, we report a high-quality reference genome of P. notoginseng, with a genome size up to 2.66 Gb and a contig N50 of 1.12 Mb, produced with third-generation PacBio sequencing technology. This is the first chromosome-level genome assembly for the genus Panax. Through genome evolution analysis, we explored phylogenetic and whole-genome duplication events and examined their impact on saponin biosynthesis. We performed a detailed transcriptional analysis of P. notoginseng and explored gene-level mechanisms that regulate the formation of characteristic tubercles. Next, we studied the biosynthesis and regulation of saponins at temporal and spatial levels. We combined multi-omics data to identify genes that encode key enzymes in the P. notoginseng terpenoid biosynthetic pathway. Finally, we identified five glycosyltransferase genes whose products catalyzed the formation of different ginsenosides in P. notoginseng. The genetic information obtained in this study provides a resource for further exploration of the growth characteristics, cultivation, breeding, and saponin biosynthesis of P. notoginseng.

Aims: Determine whether salicylic acid (SA) can alleviate the inhibitory effects of Al stress on dry matter accumulation in Panax notoginseng, and to investigate the mechanism by which the SA regulates photosynthesis and carbohydrate metabolism. Methods: Effects of SA on the biomass of P. notoginseng and the concentration of Al in leaves under Al stress were evaluated. SA and the scavenger paclobutrazol (PAC, SA synthetic inhibitor) were used to assess the effects of SA on photosynthesis and the metabolism of total nonstructural carbohydrates (TNC) in P. notoginseng. Results: SA reduced Al by 13.23% in the leaves of P. notoginseng under Al stress. It also promoted the synthesis of carbohydrates in the leaves and their transport to the roots. Additionally, SA alleviated the Al-induced reduction of chlorophyll (Chl) by upregulating the expression of Chl synthesis genes (CHLM, CHLG, HEMB1, HEMC, and HEME) and downregulating the degradation genes (CLH2 and PPH1). Concomitantly, the rubisco activase (RCA) and rubisco enzyme activities were promoted by upregulating the expressions of the RCA, rbcL, and rbcS genes via treatment with SA, thereby restoring the synthesis and metabolism of TNC. Furthermore, SA attenuated the decrease in photosynthetic capacity and photosynthesis system II photochemistry efficiency in Al-stressed plants. Furthermore, SA significantly reduced the H2O2 concentration by 12.22% under Al stress. Conclusions: By regulating photosynthesis-related genes and photochemical processes, SA promoted photosynthesis and enhanced leaf carbohydrate synthesis under Al stress. Thus, SA enhanced the production of P. notoginseng biomass, ultimately reducing the inhibitory effects of Al. [ABSTRACT FROM AUTHOR]

Abstract Based on transcriptome analysis and RT-PCR techniques, a PR10 gene was isolated from P. notoginseng root and named PnPR10. Bioinformatics and phylogenetic tree analyses revealed that the open reading frame (ORF) of PnPR10 was 465 bp in length, encoding 154 amino acids and containing one typical conserved domain of the pathogenesis-related protein Bet v I family, with high similarity to the gene from P. ginseng. Using the genome walking method, a 458 bp promoter upstream of the PnPR10 transcription start site was isolated from P. notoginseng root genomic DNA by hiTAIL-PCR. The PnPR10 promoter contained multiple cis -acting regulatory elements. The CGTCA-motif and TGACG-motif, which have been shown to play important roles in response to MeJA, were identified. The expression of PnPR10 can be induced by typical root rot disease pathogens (F. solani and C. destructans). The purified recombinant PnPR10 protein could clearly inhibit the growth of two pathogens. The results demonstrate that the PnPR10 gene is involved in the defense response against root rot disease pathogens. This experiment lays a theoretical foundation for revealing the mechanism of resistance in P.notoginseng. Highlights • PnPR10 and its promoter was isolated from P.notoginseng , the CGTCA-motif and TGACG-motif'response to MeJA were identified. • PnPR10 could inhibit growth of pathogens that can induce its expression. It may participate in defense response to pathogens. [ABSTRACT FROM AUTHOR]

Aims: Salicylic acid (SA) and nitric oxide (NO) are key signal molecules involved in the reduction of Al accumulation in many plants. The purpose of this study was to investigate whether they could reduce the root content of Al and/or its binding to the root cell wall (CW) fractions in Panax notoginseng, and to investigate the corresponding regulatory mechanisms.Methods: Effects of Al treatments on the endogenous SA and NO contents of P. notoginseng were detected. Exogenous SA and paclobutrazol (PAC, a SA synthesis inhibitor) treatments were conducted to test the effects on endogenous NO content; exogenous sodium nitroprusside (SNP, a NO doner) and 2-phenyl-4,4,5,5-tetramethyl- imidazoline-1-oxyl-3-oxyde (cPTIO, a NO synthesis inhibitor) treatments were conducted to test the effects on endogenous SA content. Pectin methyltransferase (PMT) and pectin methylesterase (PME) activity and the gene expression, pectin methylesterification degree (PMD), pectin content, and the accumulation of Al in roots were also studied under the treatments described above.Results: Al stress induced a significant increase of the activity and expression of phenylalanine ammonia-lyase (PAL), and promoted the significant increase of endogenous SA content of P. notoginseng roots. The Al promoted accumulation of endogenous NO could be enhanced by exogenous SA treatment, but was reduced by PAC. Accumulation of endogenous NO that promoted by Al could be enhanced by exogenous SA treatment, but was reduced by PAC treatment. However, SNP or cPTIO treatments had no significant effect on the Al-induced endogenous SA content of P. notoginseng. This showed that NO acted downstream of SA signaling of P. notoginseng under Al stress. Al stress can increase the activity and genes expression of PME in the roots of P. notoginseng, reduce PMD, increase CW pectin content, and thus, the binding capacity of CW pectin to Al was enhanced in P. notoginseng roots. Exogenous SA or SNP both reduced the Al-binding capacity of root CW pectin by decreasing the pectin content, and increased the PMD by inhibiting the genes expression and activity of PME. The effects of PAC or cPTIO on the above-mentioned indicators under Al stress were opposite to that of exogenous SA or SNP treatments.Conclusions: The Al stress induced accumulation of pectin and the reduction of PMD in the root CW of P. notoginseng could be reversed by the treatments of exogenous SA or SNP, then the Al contents in root CW pectin were reduced. Al stress activated the endogenous SA and NO signaling pathways in P. notoginseng, and NO acted downstream of SA. It showed that the Al-activated NO-SA signaling pathway contributed in the reduction of Al binding to the root under Al stress. [ABSTRACT FROM AUTHOR]

Endophytes in plants may be co-producer of the bioactive compounds of their hosts. We conducted a study to bioprospect for saponin-producing endophytic fungi from Panax notoginseng and evaluate the antimicrobial activity of saponins. Two novel fungal endophytes, Fusarium sp. PN8 and Aspergillus sp. PN17, were isolated from traditional Chinese medicinal herb P. notoginseng. After eight days of fermentation, the total saponins produced in the culture broth of PN8 and PN17 were 1.061 and 0.583 mg mL−1, respectively. The saponin extracts exhibited moderate to high (inhibition zone diameter 15.7–28.4 mm, MIC 1.6–12.5 mg mL−1) antimicrobial activity against pathogens tested. Further analysis showed that triterpenoid saponins produced by Fusarium PN8 were Rb1, Rd and 20(S)-Rg3, while Aspergillus PN17 had the ability to synthesise ginsenoside Re, Rd and 20(S)-Rg3. The isolated endophytes may be used as potential sources for microbial production of plant secondary metabolites and for antimicrobial agents. [ABSTRACT FROM AUTHOR]

Rhizosphere and endophytic fungal communities are considered critically important for plant health and soil fertility. In response to continuous cropping, Panax notoginseng becomes vulnerable to attack by fungal pathogens. In the present study, culture-independent Illumina MiSeq was used to investigate the rhizospheric and root endophytic fungi in response to continuous Panax notoginseng cropping practices. The results demonstrated that fungal diversity is increased inside the roots and in rhizospheric. Ascomycota , Zygomycota , Basidiomycota and Chytridiomycota were the dominant phyla detected during the continuous cropping of Panax notoginseng . The fungal diversity in the rhizospheric soil and roots of root-rot P. notoginseng plants are less than that of healthy plants in the same cultivating year, thus showing that root-rot disease also affects the community structure and diversity of rhizospheric and root endophytic fungi. Similarities in the major fungal components show that endophytic fungal communities are similar to rhizospheric soil fungal community based on a specialized subset of organisms. Canonical correspondence analysis on the fungal communities in root-rot rhizospheric from both healthy plants and rotation soils reveals that the soil pH and organic matter have the greatest impact upon the microbial community composition during continuous cropping, whereas soil nutrition status does not significantly affect the fungal community composition in response to continuous cropping practices. In addition, the results suggest that the unclassified genera Leotiomycetes, Cylindrocarpon , Fusarium and Mycocentrospora are shown as the potential pathogens which are responsible for the obstacles in continuous cropping of P. notoginseng . Further exploration of these potential pathogens might be useful for the biological control of continuous cropping of P. notoginseng . [ABSTRACT FROM AUTHOR]

Rhizosphere and root-associated microbial communities are known to be related to soil-borne disease and plant health. In the present study, the microbial communities in rhizosphere soils and roots of both healthy and diseased Panax notoginseng were analyzed by high-throughput sequencing of 16S rRNA for bacteria and 18S rRNA internal transcribed spacer for fungi, to reveal the relationship of microbial community structure with plant health status. In total, 5593 bacterial operational taxonomic units (OTUs) and 963 fungal OTUs were identified in rhizosphere soils, while 1794 bacterial and 314 fungal OTUs were identified from root samples respectively. Principal coordinate analysis separated the microbial communities both in the rhizosphere soils and roots of diseased P. notoginseng from healthy plants. Compared to those of healthy P. notoginseng, microbial communities in rhizosphere soils and roots of diseased plants showed a decrease in alpha diversity. By contrast, bacterial community dissimilarity increased and fungal community dissimilarity decreased in rhizosphere soils of diseased plants, while both bacterial and fungal community dissimilarity in roots showed no significant difference between healthy and diseased plants. Redundancy analysis at the phylum level showed that mycorrhizal colonization and soil texture significantly affected microbial community composition in rhizosphere soils, whereas shoot nutrition status had a significant effect on microbial community composition in root samples. Our study provided strong evidence for the hypothesis that microbial diversity could potentially serve as an indicator for disease outbreak of medicinal plants, and supported the ecological significance of microbial communities in maintaining plant healthy and soil fertility. [ABSTRACT FROM AUTHOR]

Soil fumigation with chloropicrin (CP) is an effective means of overcoming continuous cropping obstacles (CCO) in Panax notoginseng and improving its yield and quality. CP fumigation can change the microbial community of soil. Therefore, a key step after CP fumigation is the rapid restoration of soil microorganisms and the promotion of beneficial microorganism proliferation as the dominant flora. In this study, continuously cropped soil of P. notoginseng was fumigated with CP, and general organic fertilizer (GOF) or microbial organic fertilizer (MOF) was used to restore soil microorganisms after fumigation. Soil physical and chemical properties, soil microorganisms, and quality of P. notoginseng were investigated. The application of MOF and GOF after CP fumigation promoted increases in soil nitrogen (9.88% and 8.21%, respectively), phosphorus (21.39% and 11.57%, respectively), potassium (7.99% and 2.75%, respectively), and the quality of P. notoginseng ; it also promoted the accumulation of saponins in the main roots (23.62% and 9.12%, respectively). Application of MOF and GOF can restore the diversity of microorganisms in the soil. MOF increased the relative abundance of the beneficial soil microorganisms Glomeromycota , Mortierellomycota , Humicola and Bacillus , thereby lowering the relative abundance of the harmful Ascomycota and Fusarium relative to GOF. In summary, CP fumigation reduces the diversity of microorganisms in the soil. The addition of organic fertilizer can promote microbial diversity and increase the relative abundance of beneficial species. Moreover, the promotion effect of MOF is better than that of GOF, thereby improving soil fertility and ultimately promoting the quality and yield of P. notoginseng. [Display omitted] • Microbial organic fertilizer relieved the decrease of microbial diversity after chloropicrin fumigation. • Microbial organic fertilizer increased the beneficial microorganisms; reduced the harmful microorganisms. • Microbial organic fertilizer enhanced the soil nutrient content; promoting the yield and saponin content. • Use of chloropicrin and microbial organic fertilizer is an effective way overcoming continuous cropping obstacles. [ABSTRACT FROM AUTHOR]