Biochar increases Panax notoginseng's survival under continuous cropping by improving soil properties and microbial diversity.

Replant problem is widespread in agricultural production and causes serious economic losses, which has limited sustainable cultivation of Panax notoginseng (PN), a well-known medicinal plant in Asia. Here we conducted a field experiment to investigate the effectiveness and possible mechanisms of biochar to improve its survival under continuous cropping. Biochar from tobacco stems was applied at 4 rates of 9.0, 12, 15, and 18 t/ha to a soil where PN has been continuously cultivated for 10 years. After 18 months, soil properties, 5 allelochemicals, including p-hydroxybenzoic acid, vanillic acid, syringic acid, p-coumaric acid, and ferulic acid, key pathogen Fusarium oxysporum, microbial community, and PN survival rate were investigated. Our results show that 10 years' continuous PN cropping led to soil acidification, accumulation of NH4+-N and F. oxysporum, and low PN survival rate. However, biochar increased its survival rate from 6.0% in the control to 69.5% under 15 t/ha treatment. Moreover, soil pH, available P and K, organic matter content, and microbial diversity were increased while NH4+-N and allelochemicals vanillic acid and syringic acid contents were decreased under biochar treatment (P<0.05). Soil available K increased from 177 to 283 mg·kg-1 while NH4+-N decreased from 6.73 to 4.79 mg·kg-1 under 15 t/ha treatment. Further, soil pH, available P and K, and microbial diversity (bacteria and fungi) were positively correlated with PN survival rate, however, NH4+-N content was negatively correlated (P<0.05). Our study indicates that biochar effectively increased the survival rate of Panax notoginseng under continuous cropping by improving soil properties and microbial diversity.

Impact of rhizosphere microorganisms on arsenic (As) transformation and accumulation in a traditional Chinese medical plant.

Panax notoginseng is an important traditional medicinal plant, but the commercial value is threatened by root-rot disease caused by rhizosphere microbes and a potential health risk caused by plant arsenic (As) accumulation. Whether rhizospheric microbes isolated from P. notoginseng rhizosphere soil could impact As uptake and transport into P. notoginseng is not yet known. Among the three root-rot disease-causing pathogens Fusarium flocciferum (PG 1), Fusarium oxysporum (PG 2), and Fusarium solani (PG 3) and one root-rot disease biocontrol fungus Trichoderma koningiopsis (FC 1) and five biocontrol-exerting bacterial species Bacillus siamensis (BC 1), Delftia acidovorans (BC 2), Brevibacillus formosus (BC 3), Mortierella alpine (BC 4), and Bacillus subtilis (BC 5), one As-resistant pathogen and four biocontrol microorganisms with As-resistant ability were identified. The As-transforming ability of the identified fungi and bacteria was ranked in the order of FC 1 > PG 1 and BC 2 > BC 3 > BC 1, respectively. Then, the As-resistant biocontrol and pathogenic microbes were initiated to colonize the rhizosphere of 1-year-old P. notoginseng seedlings growing in artificially As(V)-contaminated soil to evaluate the impact of microbe inoculation on P. notoginseng As uptake and transport capacity. Concentration of As in P. notoginseng tissues decreased in the order of the sequence stem > root > leaf. Compared to treatment without colonization by microorganism, inoculation with microorganisms increased As root uptake efficiency and root As concentration, especially under treatment of inoculation by BC 2 and PG 1 + BC 2. As transport efficiency from root to stem decreased by inoculation with microorganism, especially under treatment with inoculation of BC 2 and PG 1 + BC 2. However, the impact of microorganism colonization on As stem to leaf transport efficiency was not obvious. In summary, inoculation with rhizosphere microbes may increase As accumulation in P. notoginseng root, especially when using bacteria with high As transformation ability. Therefore, it is necessary to evaluate the As transformation capacity before applying biological control microorganism to the rhizosphere of P. notoginseng.

Myrothins A-F from Endophytic Fungus Myrothecium sp. BS-31 Harbored in Panax notoginseng.

Endophytic fungi play important roles for host's stress tolerance including invasion by pathogenic microbes. Small molecules are common weapons in the microbe-microbe interactions. Panax notoginseng is a widely used traditional Chinese medicinal plant and harbors many endophytes, some exert functions against pathogens. Here, we report six new compounds named myrothins A-F (1-6) produced by Myrothecium sp. BS-31, an endophyte isolated from P. notoginseng, and their antifungal activities against pathogenic fungi causing host root-rot disease. Their structures were elucidated with analysis of spectroscopic data including 1D and 2D NMR, HR-ESI-MS. Myrothins B (2) and E (5) showed the weak activity against Fusarium oxysporum and Phoma herbarum, and myrothins F (6) showed weak activity against F. oxysporum.

Nocardia panacis sp. nov., a novel actinomycete with antiphytopathogen activity isolated from the rhizosphere of Panax notoginseng.

Strain YIM PH21724T was isolated from the rhizosphere of Panax notoginseng. Phylogenetic analyses based on 16S rRNA gene sequences showed that the strain exhibits close phylogenetic relatedness to Nocardia kroppenstedtii N1286T (97.70%), Nocardia farcinica NCTC 11134T (97.67%) and Nocardia puris DSM 44599T (97.40%). The menaquinones were identified as MK-9 (H4), MK-8 (H4, ω-cyclo) and MK-8 (H4), and the major fatty acids (> 10%) were identified as C16:0, C18:1 ω9c and C18:0 10-methyl. The polar lipids were found to be composed of diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol, phosphatidylinositol mannosides and an unidentified lipid. The G + C content of the genomic DNA was determined to be 67.01 mol%. The phenotypic, chemotaxonomic, phylogenetic and genomic results clearly show strain YIM PH21724T should be classified in the genus Nocardia and represents a novel species, for which the name Nocardia panacis sp. nov. is proposed. The type strain is YIM PH21724T (= DSM 105904T = KCTC 49030T = CCTCC AA 2017043T).

Novel Isochroman Dimers from Stachybotrys sp. PH30583: Fermentation, Isolation, Structural Elucidation and Biological Activities.

The rare anishidiol and five new isochromans, including three novel dimers with unprecedented skeletons, were isolated from Stachybotrys sp. PH30583. Their structures were determined by spectral analyses. The bioactivities of these compounds were also investigated. The dimers (6-10) inhibited acetylcholinesterase at 50 µM, but the monomers did not. To investigate the biogenesis of the novel dimers, a time-course investigation of metabolite production was undertaken.

Koningiopisins A-H, Polyketides with Synergistic Antifungal Activities from the Endophytic Fungus Trichoderma koningiopsis.

Eight new fungal polyketides named koningiopisins A-H (1-8) and four previously known polyketides (9-12) were isolated from the endophytic fungus Trichoderma koningiopsis YIM PH 30002. Their structures were elucidated using extensive spectral data interpretation, and their antifungal and synergistic activities were also evaluated. Koningiopisin C (3) exhibited in vitro antifungal activity against the phytopathogenic fungus Plectosphaerella cucumerina with an MIC of 16 µg/mL. Although the antifungal activities of single compounds were not obvious, a mixture of six compounds (4-9) exhibited potent synergistic antifungal activity against P. cucumerina with an MIC of 16 µg/mL, and the antifungal activity of the mixture of any two compounds with a 1:1 ratio was better than that observed from the individual compound. The synergistic biological activity of the metabolites in YIM PH 30002 demonstrates the significant ecological function of the endophyte for its host plant, and provides additional insight into the search for and development of agents for biological control.

[Population distribution and antimicrobial activities of endophytes in Toddalia asiatica].

OBJECTIVE: To study the population composition and antimicrobial activities of endophytes in medicinal plant Toddalia asiatica. METHODS: Endophytes were isolated from T. asiatica by using an exterior sterilization method, in combination with adding antimicrobial agents. Endophytes were classified and identified by morphological and molecular characters. Antimicrobial activities of endophytes were measured by using paper disc diffusion method. RESULTS: Three strains of endophytic bacteria, one strain of endophytic actinomyces and 82 strains of endophytic fungi were isolated from T. asiatica. Fusarium, Pestalotiopsis, and Aspergillus were the dominant populations in T. asiatica. Antimicrobial activities of these endophytes were measured against 30 pathogenic microbes, and 18 strains possess substantial inhibitory activities, of which 16 strains were endophytic fungi belonging to 11 genera. CONCLUSION: Endophytic strains with antimicrobial activities were obtained to explore the application of endophytic resources from T. asiatica.

Cyclonerol derivatives from Trichoderma longibrachiatum YM311505.

A new sesquiterpene, 10,11-dihydrocyclonerotriol (1), together with two known compounds, catenioblin C (2) and sohirnone A (3), were isolated from Trichoderma longibrachiatum YM311505, an endophytic fungus of Azadirachta indica. Their structures were characterized and identified by spectral analysis. Compounds 1-3 exhibited antifungal activities against Pyricularia oryzae and Candida albicans.

[Identification and secondary metabolites of endophytic fungal strain PR35 from Paeonia delavayi].

OBJECTIVE: To identify the endophytic fungal strain PR35 separated from Paeonia delavayi and study chemical constituents of its secondary metabolites. METHOD: The fungal strain PR35 was identified by morphological observation and ITS rDNA sequence analysis. Various chromatographic methods were adopted to separate and purify its secondary metabolites, and their structures were identified by physiochemical properties and spectral data RESULT: The fungal strain PR35 was identified as Trichoderma longibrachiatum. Five compounds were separated from fermentation products of fungal strain PR35 and identified as 1-(2,6-dihydroxyphenyl)-3-hydroxybutan-1-one (1), 1-(2,6-dihydroxypheny) propan-1-one (2), 1-(2,4,6-trihydroxyphenyl) butan-1-one (3), 4-methoxy-1-naphthol (4), and cerevisterol (5). Among them, compounds 1-3 showed notable antifungal activities against Botrytis cinerea, Fusarium avenaceum and Hormodendrum compactum. CONCLUSION: The endophytic fungus T. longibrachiatum was separated from the plant P. delavayi for the first time. Five compounds were first separated from endophytic fungus of P. delavayi. Among them, compound 4 was separated from microbial fermentation products for the first time.

A new sesquiterpenoid from Ligusticum chuanxiong Hort.

A new sesquiterpenoid named (-)-alloaromadendrane-4ß,10α,13,15-tetrol was isolated from the rhizome of Ligusticum chuanxiong Hort., together with two known compounds, campest-4-en-3-one and 3-carboxyethyl-phthalide. Their structures were elucidated on the basis of spectroscopic and chemical analysis. All the compounds showed mild antimicrobial activity.