Zno nanoparticles: improving photosynthesis, shoot development, and phyllosphere microbiome composition in tea plants.

BACKGROUND: Nanotechnology holds revolutionary potential in the field of agriculture, with zinc oxide nanoparticles (ZnO NPs) demonstrating advantages in promoting crop growth. Enhanced photosynthetic efficiency is closely linked to improved vigor and superior quality in tea plants, complemented by the beneficial role of phyllosphere microorganisms in maintaining plant health. However, the effects of ZnO NPs on the photosynthesis of tea plants, the sprouting of new shoots, and the community of phyllosphere microorganisms have not been fully investigated. RESULTS: This study investigated the photosynthetic physiological parameters of tea plants under the influence of ZnO NPs, the content of key photosynthetic enzymes such as RubisCO, chlorophyll content, chlorophyll fluorescence parameters, transcriptomic and extensive targeted metabolomic profiles of leaves and new shoots, mineral element composition in these tissues, and the epiphytic and endophytic microbial communities within the phyllosphere. The results indicated that ZnO NPs could enhance the photosynthesis of tea plants, upregulate the expression of some genes related to photosynthesis, increase the accumulation of photosynthetic products, promote the development of new shoots, and alter the content of various mineral elements in the leaves and new shoots of tea plants. Furthermore, the application of ZnO NPs was observed to favorably influence the microbial community structure within the phyllosphere of tea plants. This shift in microbial community dynamics suggests a potential for ZnO NPs to contribute to plant health and productivity by modulating the phyllosphere microbiome. CONCLUSION: This study demonstrates that ZnO NPs have a positive impact on the photosynthesis of tea plants, the sprouting of new shoots, and the community of phyllosphere microorganisms, which can improve the growth condition of tea plants. These findings provide new scientific evidence for the application of ZnO NPs in sustainable agricultural development and contribute to advancing research in nanobiotechnology aimed at enhancing crop yield and quality.

Biocontrol potential of plant growth-promoting rhizobacteria against plant disease and insect pest.

Biological control is a promising approach to enhance pathogen and pest control to ensure high productivity in cash crop production. Therefore, PGPR biofertilizers are very suitable for application in the cultivation of tea plants (Camellia sinensis) and tobacco, but it is rarely reported so far. In this study, production of a consortium of three strains of PGPR were applied to tobacco and tea plants. The results demonstrated that plants treated with PGPR exhibited enhanced resistance against the bacterial pathogen Pseudomonas syringae (PstDC3000). The significant effect in improving the plant's ability to resist pathogen invasion was verified through measurements of oxygen activity, bacterial colony counts, and expression levels of resistance-related genes (NPR1, PR1, JAZ1, POD etc.). Moreover, the application of PGPR in the tea plantation showed significantly reduced population occurrences of tea green leafhoppers (Empoasca onukii Matsuda), tea thrips (Thysanoptera:Thripidae), Aleurocanthus spiniferus (Quaintanca) and alleviated anthracnose disease in tea seedlings. Therefore, PGPR biofertilizers may serve as a viable biological control method to improve tobacco and tea plant yield and quality. Our findings revealed part of the mechanism by which PGPR helped improve plant biostresses resistance, enabling better application in agricultural production.

Automated detection of selected tea leaf diseases in Bangladesh with convolutional neural network.

Globally, tea production and its quality fundamentally depend on tea leaves, which are susceptible to invasion by pathogenic organisms. Precise and early-stage identification of plant foliage diseases is a key element in preventing and controlling the spreading of diseases that hinder yield and quality. Image processing techniques are a sophisticated tool that is rapidly gaining traction in the agricultural sector for the detection of a wide range of diseases with excellent accuracy. This study focuses on a pragmatic approach for automatically detecting selected tea foliage diseases based on convolutional neural network (CNN). A large dataset of 3330 images has been created by collecting samples from different regions of Sylhet division, the tea capital of Bangladesh. The proposed CNN model is developed based on tea leaves affected by red rust, brown blight, grey blight, and healthy leaves. Afterward, the model's prediction was validated with laboratory tests that included microbial culture media and microscopic analysis. The accuracy of this model was found to be 96.65%. Chiefly, the proposed model was developed in the context of the Bangladesh tea industry.

Effects of solid-state fermentation with Aspergillus cristatus (MK346334) on the dynamics changes in the chemical and flavor profile of dark tea by HS-SPME-GC-MS, HS-GC-IMS and electronic nose.

Aspergillus cristatus, the predominant microbe of Fuzhuan brick tea (FBT), is responsible for the creation of distinctive golden flower and unique floral aroma of FBT. The present study examined the alterations in chemical and aromatic components of raw dark tea by solid-state fermentation using A. cristatus (MK346334), the strain isolated from FBT. As results, catechins, total ployphenols, total flavonoids, theaflavins, thearubigins and antioxidant activity were significantly reduced after fermentation. Moreover, 112 and 76 volatile substances were identified by HS-SPME-GC-MS and HS-GC-IMS, respectively, primarily composed of alcohols, ketones, esters and aldehydes. Furthermore, the calculation of odor activity values revealed that 19 volatile chemicals, including hexanal, heptanal, linalool and methyl salicylate, were the main contributors to the floral, fungal, woody and minty aroma of dark tea. The present research highlights the pivotal role played by the fermentation with A. cristatus in the chemical composition, antioxidant property and distinctive flavor of dark tea.

Dynamic changes and correlation analysis of microorganisms and flavonoids/ amino acids during white tea storage.

White tea stored for various times have different flavors. However, the mechanism of flavor conversion remains elusive. Flavonoids and amino acids are two typical flavor components in tea. Herein, the contents of 46 flavonoids and 40 amino acids were measured in white tea (Shoumei) stored for 1, 3, 5 and 7 years, respectively. L-tryptophan, L-ornithine and L-theanine contribute to the refreshing taste of Shoumei 1 and 3. Quercetin, rutin and hesperidin contribute to aging charm and grain aroma of Shoumei 5 and 7. 306 bacterial OTUs and 268 fungal OTUs core microbiota existed in all samples. Interestingly, white teas contained higher richness of fungi than bacteria. The correlation analysis showed that the cooperation with bacteria and fungi may result in the flavonoids and amino acids composition changes in white teas during storage. Overall, this study provides new insights into flavor conversion of white tea during storage.

Tea and Pleurotus ostreatus intercropping modulates structure of soil and root microbial communities.

Intercropping with Pleurotus ostreatus has been demonstrated to increase the tea yield and alleviate soil acidification in tea gardens. However, the underlying mechanisms remain elusive. Here, high-throughput sequencing and Biolog Eco analysis were performed to identify changes in the community structure and abundance of soil microorganisms in the P. ostreatus intercropped tea garden at different seasons (April and September). The results showed that the soil microbial diversity of rhizosphere decreased in April, while rhizosphere and non-rhizosphere soil microbial diversity increased in September in the P. ostreatus intercropped tea garden. The diversity of tea tree root microorganisms increased in both periods. In addition, the number of fungi associated with organic matter decomposition and nutrient cycling, such as Penicillium, Trichoderma, and Trechispora, was significantly higher in the intercropped group than in the control group. Intercropping with P. ostreatus increased the levels of total nitrogen (TN), total phosphorus (TP), and available phosphorus (AP) in the soil. It also improved the content of secondary metabolites, such as tea catechins, and polysaccharides in tea buds. Microbial network analysis showed that Unclassified_o__Helotiales, and Devosia were positively correlated with soil TN and pH, while Lactobacillus, Acidothermus, and Monascus were positively correlated with flavone, AE, and catechins in tea trees. In conclusion, intercropping with P. ostreatus can improve the physical and chemical properties of soil and the composition and structure of microbial communities in tea gardens, which has significant potential for application in monoculture tea gardens with acidic soils.

Soil Microbial Community Characteristics and Their Effect on Tea Quality under Different Fertilization Treatments in Two Tea Plantations.

Fertilization is an essential aspect of tea plantation management that supports a sustainable tea production and drastically influences soil microbial communities. However, few research studies have focused on the differences of microbial communities and the variation in tea quality in response to different fertilization treatments. In this work, the soil fertility, tea quality, and soil microbial communities were investigated in two domestic tea plantations following the application of chemical and organic fertilizers. We determined the content of mineral elements in the soil, including nitrogen, phosphorus, and potassium, and found that the supplementation of chemical fertilizer directly increased the content of mineral elements. However, the application of organic fertilizer significantly improved the accumulation of tea polyphenols and reduced the content of caffeine. Furthermore, amplicon sequencing results showed that the different ways of applying fertilizer have limited effect on the alpha diversity of the microbial community in the soil while the beta diversity was remarkably influenced. This work also suggests that the bacterial community structure and abundance were also relatively constant while the fungal community structure and abundance were dramatically influenced; for example, Chaetomiaceae at the family level, Hypocreaceae at the order level, Trichoderma at the genus level, and Fusarium oxysporum at the species level were predominantly enriched in the tea plantation applying organic fertilizer. Moreover, the bacterial and fungal biomarkers were also analyzed and it was found that Proteobacteria and Gammaproteobacteria (bacteria) and Tremellomycetes (fungi) were potentially characterized as biomarkers in the plantation under organic fertilization. These results provide a valuable basis for the application of organic fertilizer to improve the soil of tea plantations in the future.

Exploring the dynamics of ISR signaling in maize upon seed priming with plant growth promoting actinobacteria isolated from tea rhizosphere of Darjeeling.

Plant growth-promoting rhizobacteria (PGPR) offer an eco-friendly alternative to agrochemicals for better plant growth and development. Here, we evaluated the plant growth promotion abilities of actinobacteria isolated from the tea (Camellia sinensis) rhizosphere of Darjeeling, India. 16 S rRNA gene ribotyping of 28 isolates demonstrated the presence of nine different culturable actinobacterial genera. Assessment of the in vitro PGP traits revealed that Micrococcus sp. AB420 exhibited the highest level of phosphate solubilization (i.e., 445 ± 2.1 µg/ml), whereas Kocuria sp. AB429 and Brachybacterium sp. AB440 showed the highest level of siderophore (25.8 ± 0.1%) and IAA production (101.4 ± 0.5 µg/ml), respectively. Biopriming of maize seeds with the individual actinobacterial isolate revealed statistically significant growth in the treated plants compared to controls. Among them, treatment with Paenarthrobacter sp. AB416 and Brachybacterium sp. AB439 exhibited the highest shoot and root length. Biopriming has also triggered significant enzymatic and non-enzymatic antioxidative defense reactions in maize seedlings both locally and systematically, providing a critical insight into their possible role in the reduction of reactive oxygen species (ROS) burden. To better understand the role of actinobacterial isolates in the modulation of plant defense, three selected actinobacterial isolates, AB426 (Brevibacterium sp.), AB427 (Streptomyces sp.), and AB440 (Brachybacterium sp.) were employed to evaluate the dynamics of induced systemic resistance (ISR) in maize. The expression profile of five key genes involved in SA and JA pathways revealed that bio-priming with actinobacteria (Brevibacterium sp. AB426 and Brachybacterium sp. AB440) preferably modulates the JA pathway rather than the SA pathway. The infection studies in bio-primed maize plants resulted in a delay in disease progression by the biotrophic pathogen Ustilago maydis in infected maize plants, suggesting the positive efficacy of bio-priming in aiding plants to cope with biotic stress. Conclusively, this study unravels the intrinsic mechanisms of PGPR-mediated ISR dynamics in bio-primed plants, offering a futuristic application of these microorganisms in the agricultural fields as an eco-friendly alternative.

Emergence of Lasiodiplodia theobromae induced leaf necrosis in tea (Camellia sinensis [L.] O. Kuntze) from India.

The tea plant, Camellia sinensis [L.] O. Kuntze, is a vital global agricultural commodity, yet faces challenges from fungal infections, which affects its production. To reduce the loss in the tea production, the fungal infections must be removed which is managed with fungicides, which are harmful to the environment. Leaf necrosis, which decreases tea quality and quantity, was investigated across Assam, revealing Lasiodiplodia theobromae as the causative agent. Pathogenicity tests, alongside morphological and molecular analyses, confirmed its role in leaf necrosis. Genome and gene analysis of L. theobromae showed multiple genes related to its pathogenicity. The study also assessed the impact of chemical pesticides on this pathogen. Additionally, the findings in this study highlight the significance of re-assessing management approaches in considering the fungal infection in tea.

Co-occurrence network and functional profiling of the bacterial community in the industrial pile fermentation of Qingzhuan tea: Understanding core functional bacteria.

The distinct quality of Qingzhuan tea is greatly influenced by the bacterial community but was poorly characterized. Therefore, this study investigated the Co-occurrence network and functional profiling of the bacterial community, with special attention paid to core functional bacteria in the industrial pile fermentation. Microbiomics analysis indicated that Klebsiella and Pantoea dominated raw tea leaves, and were rapidly replaced by Pseudomonas in pile fermentation, but substituted mainly by Burkholderia and Saccharopolyspora in final fermented tea. Bacterial taxa were grouped into 7 modules with the dominant in module I, III, and IV, which were involved in flavor formation and biocontrol production. Functional profiling revealed that "penicillin and cephalosporin biosynthesis" increased in pile fermentation. Twelve bacterial genera were identified as core functional bacteria, in which Klebsiella, Pantoea, and Pseudomonas also dominated the pile fermentation. This work would provide theoretical basis for its chemical biofortification and quality improvement by controlling bacterial communities.

Metabonomics analysis of the flavor characteristics of Wuyi Rock Tea (Rougui) with "rock flavor" and microbial contributions to the flavor.

Wuyi Rock Tea (WRT) has different characteristics of "rock flavor" due to different production areas. In this study, we investigated the flavor characteristics and key components of "rock flavor" and the influence of microorganisms on the substances by combining metabolomics and microbiomics with the Rougui WRTs from the Zhengyan, Banyan, and Waishan production areas. The results showed that Rougui has a strong floral and fruity aroma, which is mainly brought by hotrienol, and the sweet, smooth, and fresh taste is composed of epicatechin gallate, epigallocatechin, epigallocatechin gallate, caffeine, theanine, soluble sugar, and sweet and bitter amino acids. Bacteria Chryseobacterium, Pedobacter, Bosea, Agrobacterium, Stenotrophomonas, and Actinoplanes mainly influence the production of hotrienol, epicatechin gallate, and theanine. Fungi Pestalotiopsis, Fusarium, Elsinoe, Teichospora and Tetracladium mainly influence the production of non-volatile compounds. This study provides a reference for the biological formation mechanism of the characteristic aroma of WRT's "rock falvor".

Golden-flower fungus (Eurotiwm Cristatum) presents fungal flower aroma as well as accelerates the aging of white tea (Shoumei).

Golden-flower fungus (Eurotiwm Cristatum, EC) is widely inoculated in dark tea to endow a typical fungal floral aroma. Recently, Golden Flower White Tea (GFWT), prepared by transplanting EC-mediated fermentation to white tea (Shoumei, SM) to reform the roughness and coarseness, has attracted much attention attributed to coordinated flavor. However, the bio-chemistry reactions between EC and SM, along with origination of composited aroma are still unclear. Thus, the rejected EC, GFWT leaves and stems after EC removal were separated by layer-by-layer stripping following sensory evaluation, volatiles and microstructure analysis to uncover aroma formation mechanism. In GFWT, EC presents fungal flower aroma rather than contribution of extracellular enzymes secreted by fungus in Fu brick tea. Moreover, the short "flowering process" (7 days) endows SM with a stale, jujube, and sweet aroma, which is regarded as the typical characteristic of aged white tea. This inspires EC-mediated fermentation as a promising rapid aging process.

Acidification induce chemical and microbial variation in tea plantation soils and bacterial degradation of the key acidifying phenolic acids.

Camellia sinensis is an important economic plant grown in southern subtropical hilly areas, especially in China, mainly for the production of tea. Soil acidification is a significant cause of the reduction of yield and quality and continuous cropping obstacles in tea plants. Therefore, chemical and microbial properties of tea growing soils were investigated and phenolic acid-degrading bacteria were isolated from a tea plantation. Chemical and ICP-AES investigations showed that the soils tested were acidic, with pH values of 4.05-5.08, and the pH negatively correlated with K (p < 0.01), Al (p < 0.05), Fe and P. Aluminum was the highest (47-584 mg/kg) nonessential element. Based on high-throughput sequencing, a total of 34 phyla and 583 genera were identified in tea plantation soils. Proteobacteria and Acidobacteria were the main dominant phyla and the highest abundance of Acidobacteria was found in three soils, with nearly 22% for the genus Gp2. Based on the functional abundance values, general function predicts the highest abundance, while the abundance of amino acids and carbon transport and metabolism were higher in soils with pH less than 5. According to Biolog Eco Plate™ assay, the soil microorganisms utilized amino acids well, followed by polymers and phenolic acids. Three strains with good phenolic acid degradation rates were obtained, and they were identified as Bacillus thuringiensis B1, Bacillus amyloliquefaciens B2 and Bacillus subtilis B3, respectively. The three strains significantly relieved the inhibition of peanut germination and growth by ferulic acid, p-coumaric acid, p-hydroxybenzoic acid, cinnamic acid, and mixed acids. Combination of the three isolates showed reduced relief of the four phenolic acids due to the antagonist of B2 against B1 and B3. The three phenolic acid degradation strains isolated from acidic soils display potential in improving the acidification and imbalance in soils of C. sinensis.

Analysis of the Pathogenicity and Phylogeny of Colletotrichum Species Associated with Brown Blight of Tea (Camellia sinensis) in Taiwan.

Brown blight, a destructive foliar disease of tea, has become a highly limiting factor for tea cultivation in Taiwan. To understand the population composition of the causal agents (Colletotrichum spp.), the fungal diversity in the main tea-growing regions all over Taiwan was surveyed from 2017 to 2019. A collection of 139 Colletotrichum isolates was obtained from 14 tea cultivars in 86 tea plantations. Phylogenic analysis using the ribosomal internal transcribed spacer, glutamine synthetase gene, Apn2-Mat1-2 intergenic spacer, ß-tubulin, actin, calmodulin, and glyceraldehyde-3-phosphate dehydrogenase genes together with morphological characterization revealed three species associated with brown blight of tea; namely, Colletotrichum camelliae (95.6% of all isolates), C. fructicola (3.7%), and C. aenigma (0.7%). This is the first report of C. aenigma in Taiwan. The optimal growth temperatures were 25°C for C. camelliae and 25 and 30°C for C. fructicola and C. aenigma. Although C. fructicola and C. aenigma were more adapted to high temperature, C. camelliae was the most pathogenic across different temperatures. Regardless of whether spore suspensions or mycelial discs were used, significantly larger lesions and higher disease incidences were observed for wounded than for nonwounded inoculation and for the third and fourth leaves than for the fifth leaves. Wounded inoculation of detached third and fourth tea leaves with mycelial discs was found to be a reliable and efficient method for assessing the pathogenicity of Colletotrichum spp. within 4 days. Preventive application of fungicides or biocontrol agents immediately after tea pruning and at a young leaf stage would help control the disease.

Integrated Transcriptome and Proteome Analysis Reveals that the Antimicrobial Griseofulvin Targets Didymella segeticola Beta-Tubulin to Control Tea Leaf Spot.

Because effective control measures are lacking, tea leaf spot caused by Didymella segeticola results in huge tea (Camellia sinensis) production losses on tea plantations in Guizhou Province, southwestern China. Screening for natural antimicrobial agents with higher control effects against this pathogen and studying their modes of action may contribute to disease management. Here, Penicillium griseofulvum-derived antimicrobial griseofulvin (GSF) can inhibit the hyphal growth of D. segeticola strain GZSQ-4, with a half-maximal effective concentration of 0.37 µg/ml in vitro and a higher curative efficacy at a lower dose of 25 µg/ml for detached tea twigs. GSF induces deformed and slightly curly hyphae with enlarged ends, with protoplasts agglutinated in the hyphae, and higher numbers of hyphal protuberances. GSF alters hyphal morphology and the subcellular structure's order. The integrated transcriptome and proteome data revealed that the transport of materials in cells, cellular movement, and mitosis were modulated by GSF. Molecular docking indicated that beta-tubulin was the most potent target of GSF, with a binding free energy of -13.59 kcal/mol, and microscale thermophoresis indicated that the dissociation constant (Kd) value of GSF binding to beta-tubulin 1, compared with beta-tubulin 2, was significantly lower. Thus, GSF potentially targets beta-tubulin 1 to disturb the chromosomal separation and fungal mitosis, thereby inhibiting hyphal growth.

Characterization and identification of fungicide insensitive Pestalotiopsis-like species pathogenic to tea crop in India.

Gray blight, a fungal disease caused by Pestalotiopsis-like species, is a widespread disease affecting tea crop (Camellia sinensis (L.) Kuntze) in many tea-growing countries, including India, resulting in huge losses in tea production. In India, several studies have been conducted to understand the fungal diseases of tea crop, but gray blight has not been well described in major tea growing areas such as in North Bengal, based on its geographic distribution, molecular analysis, or pathogenicity, and even fungicide resistance. The objective of this study was to identify and characterize the causative agents of gray blight disease in symptomatic leaf sample of tea crop collected from 27 tea gardens located in North Bengal, India and to evaluate some common fungicides against them in order to understand the resistance mechanism. In this study, we characterized Pestalotiopsis-like species based on the phylogenies of DNA sequences (internal transcribed spacers) and assessment of conidial characteristics. The study revealed that out of 27 isolates of gray blight pathogens, 17 belonged to the genus Pseudopestalotiopsis (Ps.), six isolates were Neopestalotiopsis, and four were Pestalotiopsis. Two novel species, Ps. thailandica and N. natalensis were introduced through this study. The most frequently isolated genus from C. chinensis was Pseudopestalotiopsis. Pathogenicity tests showed that the isolates displayed significantly different virulence when inoculated onto wounded tea leaves and the mycelial growth rate was positively correlated with pathogenicity (P < 0.01). Based on the 13 ISSR (Inter Simple Sequence Repeat) markers used and principal coordinate analysis, it was found that isolates were very diverse. Out of 27 isolates, IND0P2, DLG0P10, and BHAT0P11 isolates were insensitive against both MBC + M3 (Carbendazim + Mancozeb) and DMI (Hexaconazole) fungicides, while isolates SANY0P18, PAHG0P19, RANG0P24, and SING0P25 were insensitive only against MBC + M3 fungicide. Further, these insensitive isolates were grouped into separate clusters by ISSR, indicating their distinctiveness. However, all the evaluated isolates were susceptible to M1 (copper oxychloride) and another DMI (propiconazole) fungicides. Therefore, to manage gray blight, fungicide resistance management strategies as recommended by Fungicide Resistance Action Committee should be implemented.

Potentiality of actinobacteria to combat against biotic and abiotic stresses in tea [Camellia sinensis (L) O. Kuntze].

Tea (Camellia sinensis (L) O. Kuntze) is a long-duration monoculture crop prone to several biotic (fungal diseases and insect pest) and abiotic (nutrient deficiency, drought and salinity) stress that eventually result in extensive annual crop loss. The specific climatic conditions and the perennial nature of the tea crop favour growth limiting abiotic factors, numerous plant pathogenic fungi (PPF) and insect pests. The review focuses on the susceptibility of tea crops to PPF/pests, drought, salinity and nutrient constraints and the potential role of beneficial actinobacteria in promoting tea crop health. The review also focuses on some of the major PPF associated with tea, such as Exobasidium vexans, Pestalotiopsis theae, Colletotrichum acutatum, and pests (Helopeltis theivora). The phylum actinobacteria own a remarkable place in agriculture due to the biosynthesis of bioactive metabolites that assist plant growth by direct nutrient assimilation, phytohormone production, and by indirect aid in plant defence against PPF and pests. The chemical diversity and bioactive significance of actinobacterial metabolites (antibiotics, siderophore, volatile organic compounds, phytohormones) are valuable in the agro-economy. This review explores the recent history of investigations in the role of actinobacteria and its secondary metabolites as a biocontrol agent and proposes a commercial application in tea cultivation.

New Sorbicillinoids with Tea Pathogenic Fungus Inhibitory Effect from Marine-Derived Fungus Hypocrea jecorina H8.

Four new dimeric sorbicillinoids (1-3 and 5) and a new monomeric sorbicillinoid (4) as well as six known analogs (6-11) were purified from the fungal strain Hypocrea jecorina H8, which was obtained from mangrove sediment, and showed potent inhibitory activity against the tea pathogenic fungus Pestalotiopsis theae (P. theae). The planar structures of 1-5 were assigned by analyses of their UV, IR, HR-ESI-MS, and NMR spectroscopic data. All the compounds were evaluated for growth inhibition of tea pathogenic fungus P. theae. Compounds 5, 6, 8, 9, and 10 exhibited more potent inhibitory activities compared with the positive control hexaconazole with an ED50 of 24.25 ± 1.57 µg/mL. The ED50 values of compounds 5, 6, 8, 9, and 10 were 9.13 ± 1.25, 2.04 ± 1.24, 18.22 ± 1.29, 1.83 ± 1.37, and 4.68 ± 1.44 µg/mL, respectively. Additionally, the effects of these compounds on zebrafish embryo development were also evaluated. Except for compounds 5 and 8, which imparted toxic effects on zebrafish even at 0.625 µM, the other isolated compounds did not exhibit significant toxicity to zebrafish eggs, embryos, or larvae. Taken together, sorbicillinoid derivatives (6, 9, and 10) from H. jecorina H8 displayed low toxicity and high anti-tea pathogenic fungus potential.

Differential responses of the rhizosphere microbiome structure and soil metabolites in tea (Camellia sinensis) upon application of cow manure.

BACKGROUND: The rhizosphere is the narrow zone of soil immediately surrounding the root, and it is a critical hotspot of microbial activity, strongly influencing the physiology and development of plants. For analyzing the relationship between the microbiome and metabolome in the rhizosphere of tea (Camellia sinensis) plants, the bacterial composition and its correlation to soil metabolites were investigated under three different fertilization treatments (unfertilized, urea, cow manure) in different growing seasons (spring, early and late summer). RESULTS: The bacterial phyla Proteobacteria, Bacteroidetes, Acidobacteria and Actinobacteria dominated the rhizosphere of tea plants regardless of the sampling time. These indicated that the compositional shift was associated with different fertilizer/manure treatments as well as the sampling time. However, the relative abundance of these enriched bacteria varied under the three different fertilizer regimes. Most of the enriched metabolic pathways stimulated by different fertilizer application were all related to sugars, amino acids fatty acids and alkaloids metabolism. Organic acids and fatty acids were potential metabolites mediating the plant-bacteria interaction in the rhizosphere. Bacteria in the genera Proteiniphilum, Fermentimonas and Pseudomonas in spring, Saccharimonadales and Gaiellales in early summer, Acidobacteriales and Gaiellales in late summer regulated relative contents of organic and fatty acids. CONCLUSION: This study documents the profound changes to the rhizosphere microbiome and bacterially derived metabolites under different fertilizer regimes and provides a conceptual framework towards improving the performance of tea plantations.

Dual activity of Serratia marcescens Pt-3 in phosphate-solubilizing and production of antifungal volatiles.

BACKGROUND: Soil fertility decline and pathogen infection are severe issues for crop production all over the world. Microbes as inherent factors in soil were effective in alleviating fertility decrease, promoting plant growth and controlling plant pathogens et al. Thus, screening microbes with fertility improving and pathogen controlling properties is of great importance to humans. RESULTS: Bacteria Pt-3 isolated from tea rhizosphere showed multiple functions in solubilizing insoluble phosphate, promoting plant growth, producing abundant volatile organic compounds (VOCs) and inhibiting the growth of important fungal pathogens in vitro. According to the 16S rRNA phylogenetic and biochemical analysis, Pt-3 was identified to be Serratia marcescens. The solubilizing zone of Pt-3 in the medium of lecithin and Ca3(PO4)2 was 2.1 cm and 1.8 cm respectively. In liquid medium and soil, the concentration of soluble phosphorus reached 343.9 mg.L- 1, and 3.98 mg.kg- 1, and significantly promoted the growth of maize seedling, respectively. Moreover, Pt-3 produced abundant volatiles and greatly inhibited the growth of seven important phytopathogens. The inhibition rate ranged from 75.51 to 100% respectively. Solid phase micro-extraction coupled with gas chromatography tandem mass spectrometry proved that the antifungal volatile was dimethyl disulfide. Dimethyl disulfide can inhibit the germination of Aspergillus flavus, and severely destroy the cell structures under scanning electron microscopy. CONCLUSIONS: S. marcescens Pt-3 with multiple functions will provide novel agent for the production of bioactive fertilizer with P-solubilizing and fungal pathogens control activity.