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The spread of grape leaf diseases has a negative impact on the sustainable development of agriculture. Diseases induced by Uncinula necator significantly affect the quality of grapes. Bacillus biocontrol agents have been proven effective in disease management. However, limited research has been conducted on the impact of biocontrol agents on the assembly and potential functions of plant phyllosphere microbial communities. This study used high-throughput sequencing combined with bioinformatics analysis and culture omics technology for analysis. The results showed that biocontrol bacteria B. subtilis utilized in this study can significantly reduce the disease index of powdery mildew (p<0.05); concurrently, it exhibits a lower disease index compared to traditional fungicides. A comprehensive analysis has revealed that biocontrol bacteria have no significant impact on the diversity of phyllosphere fungi and bacteria, while fungicides can significantly reduce bacterial diversity. Additionally, biocontrol agents can increase the complexity of fungal networks and enhance the degree of modularity and stability of the bacterial network. The results also showed that the biocontrol agents, which contained a high amount of B. subtilis, were able to effectively colonize the grapevine phyllosphere, creating a microenvironment that significantly inhibits pathogenic bacteria on grape leaves while enhancing leaf photosynthetic capacity. In conclusion, biocontrol agents significantly reduce the grape powdery mildew disease index, promote a microenvironment conducive to symbiotic microorganisms and beneficial bacteria, and enhance plant photosynthetic capacity. These findings provide a basis for promoting biocontrol agents and offer valuable insights into sustainable agriculture development. [ABSTRACT FROM AUTHOR]

With the rapid expansion of artificial light in the global nocturnal environment, the ecological impacts of artificial light at night (ALAN) on plant communities have garnered increasing research interest. However, the role of phyllosphere microorganisms as mediators in the regulation between ALAN and plants remains unclear. In this study, we conducted a field experiment in natural grassland plots, employing two treatments: one with no artificial light at night (control) and another with artificial light at night (ALAN). We then investigated the response of phyllosphere microorganisms in three grassland plant species (Leymus chinensis, Vicia sepium, and Aster altaicus) to ALAN exposure. The results revealed that the constructive species L. chinensis demonstrated a markedly higher diversity of phyllosphere bacteria and fungi compared to V. sepium and A. altaicus and thus had the most abundant microbial community. However, ALAN exposure reduced the diversity of phyllosphere bacteria and fungi in all three plant species to varying degrees. ALAN induced certain changes to the phyllosphere bacterial community composition, particularly manifesting in a reduction in the abundance of beneficial bacteria, including Sphingomonas, Hymenobacter, Methylobacterium-Methylorubrum, and Bacillus. Compared with phyllosphere bacterial communities, the alterations in phyllosphere fungal communities were more sensitive, characterized by a significant decrease in the abundance of certain fungi, including Zymoseptoria, Mycosphaerella, Cladosporium, and Epicoccum. The functional predictions of phyllosphere bacteria and fungi further corroborate these conclusions. In summary, ALAN exposure may suppress the functional capacity of phyllosphere microorganisms in grassland plants while decreasing the probability of fungal pathogen occurrence.

This study aimed to examine the impact of nitrogen (N) fertilization on phyllosphere microorganisms in silage maize (Zea mays) to enhance the production of high-quality silage. The effects of different N application rates (160, 240, and 320 kg ha-1) and maturity stages (flowering and dough stages) on microbial diversity, abundance and physiochemical properties of the leaf surfaces were evaluated in a field experiment. The results showed that N application rates did not significantly impact the abundance of lactic acid bacteria (LAB), aerobic bacteria (AB), yeasts, or molds on the leaf surfaces. However, these microbes were more abundant during the flowering stage compared to the dough stage. Furthermore, the N application rate had no significant impact on inorganic phosphorus, soluble sugar, free amino acids, total phenolic content, and soluble protein concentrations, or pH levels on the leaf surfaces. Notably, these chemical indices were lower during the dough stage. The abundance of Pantoea decreased with higher N application rates, while that of other microorganisms did not changes significantly. The abundance of AB, LAB, yeasts, and molds were positively correlated with soluble sugar, soluble protein, inorganic phosphorus, free amino acids, and total phenolic concentrations on leaf surfaces. Moreover, water loss was negatively correlated with the abundance of AB, LAB, yeasts, and molds, whereas water retention capacity and stomatal density were positively correlated with microbial abundance. We recommend applying an optimal N rate of 160 kg ha-1 to silage maize and harvesting at the flowering stage is recommended. [ABSTRACT FROM AUTHOR]

Copyright of Tobacco Science & Technology is the property of Tobacco Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Tobacco target spot is a fungal disease on tobacco. In this paper, the mycelial growth rate method was used for the potential evaluation of dimetachlone to Rhizoctonia solani, and the effect of dimetachlone on the microbes of tobacco leaves after different periods of application was studied with Illumina high-throughput sequencing technology as well. Results showed that dimetachlone had strong inhibitory activity against the mycelial growth of R. solani with an EC50 value of 1.20 μg/mL and a complete inhibition of mycelial growth at 6.47 μg/mL. Within 0-18 days of treatment with 4200 g/hm² dimetachlone 40% WP, there were significant differences in microbial community structure between healthy and diseased tobacco leaves. The phyllosphere fungi in both healthy and diseased tobacco were all distributed in Thanatephorus, Alternaria, and Fusarium, the phyllosphere bacteria in tobacco leaves were Pseudomonas, Staphylococcus, and Sphingomonas. Three days after application, the relative abundance of Thanatephorus in healthy and diseased tobacco leaves decreased 12.41% and 51.62%, the relative abundance of Alternaria increased 0.54% and 0.42%, the relative abundance of Pseudomonas decreased 13.48% and 19.17%, respectively. Nine days after application, the relative abundance of Thanatephorus in healthy and diseased tobacco leaves decreased 1.38% and 47.42%, the relative abundance of Alternaria decreased 0.36% and 0.18%, the relative abundance of Pseudomonas decreased 2.73% and 2.73%, respectively. Eighteen days after application, the relative abundance of Thanatephorus in healthy and diseased tobacco leaves decreased 26.74% and 39.03%, the relative abundance of Alternaria increased 26.02% and 2.70%, the relative abundance of Pseudomonas increased 6.56% and 16.02%, respectively. The application of dimetachlone 40% WP in the field significantly suppressed the relative abundance of Thanatephorus genus in healthy and diseased tissues within 3 d, but the effect on disease tissues was greater than that on healthy leaves; it also caused changes in the structure of interleaf bacterial flora, but the effect on diseased leaves was less than that on healthy tobacco leaves. The results of the study revealed the differences in the phyllosphere microorganism communities between healthy and diseased interleaf tissues after the application of dimetachlone from a microscopic perspective, providing a scientific basis for the application of dimetachlone. [ABSTRACT FROM AUTHOR]

Introduction: The above-ground parts of terrestrial plants are collectively known as the phyllosphere. The surface of the leaf blade is a unique and extensive habitat for microbial communities. Phyllosphere bacteria are the second most closely associated microbial group with plants after fungi and viruses, and are the most abundant, occupying a dominant position in the phyllosphere microbial community. Host species are a major factor influencing the community diversity and structure of phyllosphere microorganisms. Methods: In this study, six Populus spp. were selected for study under the same site conditions and their phyllosphere bacterial community DNA fragments were paired-end sequenced using 16S ribosomal RNA (rRNA) gene amplicon sequencing. Based on the distribution of the amplicon sequence variants (ASVs), we assessed the alpha-diversity level of each sample and further measured the differences in species abundance composition among the samples, and predicted the metabolic function of the community based on the gene sequencing results. Results: The results revealed that different Populus spp. under the same stand conditions resulted in different phyllosphere bacterial communities. The bacterial community structure was mainly affected by the carbon and soluble sugar content of the leaves, and the leaf nitrogen, phosphorus and carbon/nitrogen were the main factors affecting the relative abundance of phyllosphere bacteria. Discussion: Previous studies have shown that a large proportion of the variation in the composition of phyllosphere microbial communities was explained by the hosts themselves. In contrast, leaf-borne nutrients were an available resource for bacteria living on the leaf surface, thus influencing the community structure of phyllosphere bacteria. These were similar to the conclusions obtained in this study. This study provides theoretical support for the study of the composition and structure of phyllosphere bacterial communities in woody plants and the factors influencing them. [ABSTRACT FROM AUTHOR]

Antibiotic resistance genes (ARGs) have been widely found and studied in soil and water environments. However, the propagation of ARGs in plant microbiomes has attracted insufficient attention. Plant microbiomes, especially the rhizosphere microorganisms, are closely connected with water, soil, and air, which allows ARGs to spread widely in ecosystems and pose a threat to human health after entering the human body with bacteria. Therefore, it is necessary to deeply understand and explore the dynamics and the transmission of ARGs in rhizosphere microorganisms and endophytes of plants. In this review, the transmission and influencing factors of ARGs in the microorganisms associated with plants, especially the influence of root exudates on plant microbiomes, are analyzed. Notably, the role of intrinsic genes of plants in determining root exudates and their potential effects on ARGs are proposed and analyzed. The important role of phyllosphere microorganisms and endophytes in the transmission of ARGs and co-resistance of antibiotics and other substances are also emphasized. The proliferation and transmission of ARGs associated with plant microbiomes addressed in this review is conducive to revealing the fate of ARGs in plant microorganisms and alleviating ARG pollution.

【Objective】The study was conducted to explore the phyllosphere bacterial community structure and diversity of landscaping plants in the niche, and to understand the effects of similar environmental conditions and plant characteristics on microbial community in the niche, with a view to provide references for the health management of garden plants and the exploitation of phyllosphere bacterial resources.【Method】High-throughput sequencing technology was applied to explore the bacterial community structure and diversity of Eriobotyra japonica, Magnolia grandiflora and Ficus altissima leaves facing east within 50 m radius circle of Dali University campus.【Result】Among the three garden plants, E. japonica had the highest phyllosphere bacterial diversity, followed by M. grandiflora and F. altissima. The dominant bacterial phylum of phyllosphere bacteria in different plants was Proteobacteria, and the first dominant bacterial genus was different. However, the top five dominant genera were Sphingopyxis, Methylobacterium, Spirosoma, Hymenobacter and Achromobacter. There were significant differences in phyllosphere bacterial community structure among the three plants, but the bacterial communities were similar among the leaves with different sizes of the same plant. Only E. japonica and M. grandiflora leaves had the largest phylum and genus distribution, indicating that the phyllosphere bacterial communities of evergreen broad-leaved plants was more diverse and complex than those of deciduous broad-leaved plants.【Conclusion】There were differences in the composition and diversity of phyllosphere bacterial communities among different plants, and the primary reasons for these differences were the characteristics of the plants themselves. Therefore, it is urgent to strengthen the researches on the utilization of phyllosphere bacterial resources of plants.

Phyllosphere microbial communities have an important role in plant growth and resistance to pathogen infection and are partially influenced by leaf characteristics. Pinewood nematode, Bursaphelenchus xylophilus, is one of the greatest threats to pine trees and is spreading all over the world. However, studies on the resistance of plant–microbe interactions to pathogens during the nematode's pathogenesis and the relationships of leaf chemical characteristics caused by pinewood nematode and phyllosphere microbial communities are limited. In this study, different stages of Pinus tabuliformis that were healthy or infected with B. xylophilus-associated leaf characteristics and phyllosphere bacterial and fungal communities were compared. These results demonstrated that soluble sugar and starch contents decreased based on the extent of infection. Phyllosphere microbial community changes potentially caused by B. xylophilus infection of P. tabuliformis and the fungal community compositions of healthy P. tabuliformis trees (Ya) were clearly different from diseased P. tabuliformis trees at an early stage of B. xylophilus infection (Yb) and P. tabuliformis trees in the last stage of B. xylophilus infection (Yc), particularly along the first coordinate axis. According to a linear discriminant effect size (LEfSe) analysis, the biomarker species in the phyllosphere of Yb were Acidobacteria, Deinococcus-Thermus, and Patescibacteria, while those in the phyllosphere of Ya were Proteobacteria, Aureobasidium, Dictyosporium, Alternariaster, Knufia, Microstroma, and Naganishia. Particularly at the end of PWD (pine wilt disease) infection, the majority of microbial taxa tended to co-exclude rather than co-occur with PWD infection. The result of a canonical correlation analysis (CCA) showed that the chemical properties of leaves, such as carbon and nitrogen, have significant impacts on phyllosphere microbial communities. These results expanded the possible connections between the phyllosphere communities and plant health. [ABSTRACT FROM AUTHOR]

The spread of grape leaf diseases has a negative impact on the sustainable development of agriculture. Diseases induced by Uncinula necator significantly affect the quality of grapes. Bacillus biocontrol agents have been proven effective in disease management. However, limited research has been conducted on the impact of biocontrol agents on the assembly and potential functions of plant phyllosphere microbial communities. This study used high-throughput sequencing combined with bioinformatics analysis and culture omics technology for analysis. The results showed that biocontrol bacteria B. subtilis utilized in this study can significantly reduce the disease index of powdery mildew ( p <0.05); concurrently, it exhibits a lower disease index compared to traditional fungicides. A comprehensive analysis has revealed that biocontrol bacteria have no significant impact on the diversity of phyllosphere fungi and bacteria, while fungicides can significantly reduce bacterial diversity. Additionally, biocontrol agents can increase the complexity of fungal networks and enhance the degree of modularity and stability of the bacterial network. The results also showed that the biocontrol agents, which contained a high amount of B. subtilis , were able to effectively colonize the grapevine phyllosphere, creating a microenvironment that significantly inhibits pathogenic bacteria on grape leaves while enhancing leaf photosynthetic capacity. In conclusion, biocontrol agents significantly reduce the grape powdery mildew disease index, promote a microenvironment conducive to symbiotic microorganisms and beneficial bacteria, and enhance plant photosynthetic capacity. These findings provide a basis for promoting biocontrol agents and offer valuable insights into sustainable agriculture development., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 He, Yang, Du, Du, He, Wang, Deng, Liu, He, Zhu, Zhu and Du.)

Pine wood nematode, Bursaphelenchus xylophilus, as one of the greatest threats to pine trees, is spreading all over the world. Plant microorganisms play an important role in the pathogenesis of nematodes. The phyllosphere and rhizosphere bacterial and fungal communities associated with healthy Pinus koraiensis (PKa) and P. koraiensis infected by B. xylophilus at the early (PKb) and last (PKc) stages were analyzed. Our results demonstrated that pine wood nematode (PWD) could increase the phyllosphere bacterial Pielou_e, Shannon, and Simpson index; phyllosphere fungal Chao 1 index, as well as rhizosphere bacterial Pielou_e, Shannon, and Simpson index; and rhizosphere fungal Pielou_e, Shannon, and Simpson index. What's more, slight shifts of the microbial diversity were observed at the early stage of infection, and the microbial diversity increased significantly as the symptoms of infection worsened. With the infection of B. xylophilus in P. koraiensis, Bradyrhizobium (rhizosphere bacteria), Massilia (phyllosphere bacteria), and Phaeosphaeriaceae (phyllosphere fungi) were the major contributors to the differences in community compositions among different treatments. With the infection of PWD, most of the bacterial groups tended to be co-excluding rather than co-occurring. These changes would correlate with microbial ability to suppress plant pathogen, enhancing the understanding of disease development and providing guidelines to pave the way for its possible management. [ABSTRACT FROM AUTHOR]

Grape downy mildew, caused by Plasmopara viticola (Berk. & M.A. Curtis) Berl. & De Toni 1888, is a widespread fungal disease that causes serious harm to the grape production. The long-term continuous use of chemical pesticides has caused issues with the resistance, residues and resurgence, as well as creating environmental pollution and the declining quality of the products. A biological control offers a safe and effective method to control diseases. We determined the in vitro antagonistic activity of 303 bacterial strains from infected grapevine leaves, and 12 isolates showed some level of antagonism in a detached leaf assay. Isolate SY286 reduced the disease severity in the detached leaves by 93.18%, and showed good control effects in a field assay. The scanning electron microscopy showed the damaged P. viticola cell walls when the mycelia and sporangia were treated with the fermentation liquor of isolate SY286. Furthermore, it showed an antagonistic activity against Phytophthora capsici, Phytophthora infestans, Botrytis cinerea, Fusarium oxysporum, Colletotrichum orbiculare, Trichothecium roseum, and Botryosphaeria berengeriana. The isolate was identified as Ochrobactrum sp. combined with its morphological characteristics, physiological and biochemical reactions and 16S rDNA sequence analysis, and it has the potential to control the grapevine downy mildew.

Phyllosphere microbial communities have an important role in plant growth and resistance to pathogen infection and are partially influenced by leaf characteristics. Pinewood nematode, Bursaphelenchus xylophilus, is one of the greatest threats to pine trees and is spreading all over the world. However, studies on the resistance of plant–microbe interactions to pathogens during the nematode’s pathogenesis and the relationships of leaf chemical characteristics caused by pinewood nematode and phyllosphere microbial communities are limited. In this study, different stages of Pinus tabuliformis that were healthy or infected with B. xylophilus-associated leaf characteristics and phyllosphere bacterial and fungal communities were compared. These results demonstrated that soluble sugar and starch contents decreased based on the extent of infection. Phyllosphere microbial community changes potentially caused by B. xylophilus infection of P. tabuliformis and the fungal community compositions of healthy P. tabuliformis trees (Ya) were clearly different from diseased P. tabuliformis trees at an early stage of B. xylophilus infection (Yb) and P. tabuliformis trees in the last stage of B. xylophilus infection (Yc), particularly along the first coordinate axis. According to a linear discriminant effect size (LEfSe) analysis, the biomarker species in the phyllosphere of Yb were Acidobacteria, Deinococcus-Thermus, and Patescibacteria, while those in the phyllosphere of Ya were Proteobacteria, Aureobasidium, Dictyosporium, Alternariaster, Knufia, Microstroma, and Naganishia. Particularly at the end of PWD (pine wilt disease) infection, the majority of microbial taxa tended to co-exclude rather than co-occur with PWD infection. The result of a canonical correlation analysis (CCA) showed that the chemical properties of leaves, such as carbon and nitrogen, have significant impacts on phyllosphere microbial communities. These results expanded the possible connections between the phyllosphere communities and plant health.

Imazethapyr (IM) is a widely used acetolactate synthase-inhibiting chiral herbicide. It has long-term residuals that may be absorbed by the human body through the edible parts of plants, such as vegetable leaves or fruits. Here, we selected a model plant, Arabidopsis thaliana , to determine the effects of R -IM and S -IM on its leaf structure, photosynthetic efficiency, and metabolites, as well as the structures of microorganisms in the phyllosphere, after 7 days of exposure. Our results indicated enantiomeric differences in plant growth between R -IM and S -IM; 133 µg/kg R -IM showed heavier inhibition of photosynthetic efficiency and greater changes to subcellular structure than S -IM. R -IM and S -IM also had different effects on metabolism and leaf microorganisms. S -IM mainly increased lipid compounds and decreased amino acids, while R -IM increased sugar accumulation. The relative abundance of Moraxellaceae human pathogenic bacteria was increased by R -IM treatment, indicating that R -IM treatment may increase leaf surface pathogenic bacteria. Our research provides a new perspective for evaluating the harmfulness of pesticide residues in soil, phyllosphere microbiome changes via the regulation of plant metabolism, and induced pathogenic bacterial accumulation risks. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Applied Ecology / Yingyong Shengtai Xuebao is the property of Chinese Journal of Applied Ecology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study aimed to examine the impact of nitrogen (N) fertilization on phyllosphere microorganisms in silage maize ( Zea mays ) to enhance the production of high-quality silage. The effects of different N application rates (160, 240, and 320 kg ha -1 ) and maturity stages (flowering and dough stages) on microbial diversity, abundance and physiochemical properties of the leaf surfaces were evaluated in a field experiment. The results showed that N application rates did not significantly impact the abundance of lactic acid bacteria (LAB), aerobic bacteria (AB), yeasts, or molds on the leaf surfaces. However, these microbes were more abundant during the flowering stage compared to the dough stage. Furthermore, the N application rate had no significant impact on inorganic phosphorus, soluble sugar, free amino acids, total phenolic content, and soluble protein concentrations, or pH levels on the leaf surfaces. Notably, these chemical indices were lower during the dough stage. The abundance of Pantoea decreased with higher N application rates, while that of other microorganisms did not changes significantly. The abundance of AB, LAB, yeasts, and molds were positively correlated with soluble sugar, soluble protein, inorganic phosphorus, free amino acids, and total phenolic concentrations on leaf surfaces. Moreover, water loss was negatively correlated with the abundance of AB, LAB, yeasts, and molds, whereas water retention capacity and stomatal density were positively correlated with microbial abundance. We recommend applying an optimal N rate of 160 kg ha -1 to silage maize and harvesting at the flowering stage is recommended., Competing Interests: The authors declare that they have no competing interests., (© 2023 Wu et al.)

[Display omitted] • ARGs in plant microbiomes are affected by rhizosphere microbiomes and root exudates. • The specific intrinsic genes of plants may determine the types of root exudates. • The intrinsic genes of plants may have the potential to encode antibiotic resistance. • Phyllosphere microorganisms and endophytes affect ARGs in plant microbiomes. • ARGs in plant microbiomes come from a wide range of sources. Antibiotic resistance genes (ARGs) have been widely found and studied in soil and water environments. However, the propagation of ARGs in plant microbiomes has attracted insufficient attention. Plant microbiomes, especially the rhizosphere microorganisms, are closely connected with water, soil, and air, which allows ARGs to spread widely in ecosystems and pose a threat to human health after entering the human body with bacteria. Therefore, it is necessary to deeply understand and explore the dynamics and the transmission of ARGs in rhizosphere microorganisms and endophytes of plants. In this review, the transmission and influencing factors of ARGs in the microorganisms associated with plants, especially the influence of root exudates on plant microbiomes, are analyzed. Notably, the role of intrinsic genes of plants in determining root exudates and their potential effects on ARGs are proposed and analyzed. The important role of phyllosphere microorganisms and endophytes in the transmission of ARGs and co-resistance of antibiotics and other substances are also emphasized. The proliferation and transmission of ARGs associated with plant microbiomes addressed in this review is conducive to revealing the fate of ARGs in plant microorganisms and alleviating ARG pollution. [ABSTRACT FROM AUTHOR]

Introduction: The above-ground parts of terrestrial plants are collectively known as the phyllosphere. The surface of the leaf blade is a unique and extensive habitat for microbial communities. Phyllosphere bacteria are the second most closely associated microbial group with plants after fungi and viruses, and are the most abundant, occupying a dominant position in the phyllosphere microbial community. Host species are a major factor influencing the community diversity and structure of phyllosphere microorganisms., Methods: In this study, six Populus spp. were selected for study under the same site conditions and their phyllosphere bacterial community DNA fragments were paired-end sequenced using 16S ribosomal RNA (rRNA) gene amplicon sequencing. Based on the distribution of the amplicon sequence variants (ASVs), we assessed the alpha-diversity level of each sample and further measured the differences in species abundance composition among the samples, and predicted the metabolic function of the community based on the gene sequencing results., Results: The results revealed that different Populus spp. under the same stand conditions resulted in different phyllosphere bacterial communities. The bacterial community structure was mainly affected by the carbon and soluble sugar content of the leaves, and the leaf nitrogen, phosphorus and carbon/nitrogen were the main factors affecting the relative abundance of phyllosphere bacteria., Discussion: Previous studies have shown that a large proportion of the variation in the composition of phyllosphere microbial communities was explained by the hosts themselves. In contrast, leaf-borne nutrients were an available resource for bacteria living on the leaf surface, thus influencing the community structure of phyllosphere bacteria. These were similar to the conclusions obtained in this study. This study provides theoretical support for the study of the composition and structure of phyllosphere bacterial communities in woody plants and the factors influencing them., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Liu, Zhang, Liu, Zhu, Yuan, Su and Ding.)

Vitamin B 6 (VB 6 ) comprises six interconvertible pyridine compounds (vitamers), among which pyridoxal 5′-phosphate (PLP) is a coenzyme involved in a high diversity of biochemical reactions. In plants, PLP is de novo synthesized, and pyridoxine (PN) is usually maintained as the predominant B 6 vitamer. Although the conversion from pyridoxal (PL) to PN catalyzed by PL reductase in plants has been confirmed, the enzyme itself remains largely unknown. We previously found pre-incubation at 35 °C dramatically enhanced PL reductase activity in tobacco leaf homogenate. In this study, we demonstrated that the increase in the reductase activity was a consequence of phyllosphere microbial proliferation. VB 6 was detected from tobacco phyllosphere, and PL level was the highest among three non-phosphorylated B 6 vitamers. When the sterile tobacco rich in PL were kept in an open, warm and humid environment to promote microorganism proliferation, a significant change from PL to PN was observed. Our results suggest that there may be a plant–microbe interaction in the conversion from PL to PN within tobacco phyllosphere. [ABSTRACT FROM AUTHOR]

The leaves of plants are colonized by various microorganisms. In comparison to the rhizosphere, less is known about the characteristics and ecological functions of phyllosphere microorganisms. Phyllosphere microorganisms mainly originate from soil, air, and seeds. The composition of phyllosphere microorganisms is mainly affected by ecological and abiotic factors. Phyllosphere microorganisms execute multiple ecological functions by influencing leaf functions and longevity, seed mass, fruit development, and homeostasis of host growth. A plant can respond to phyllosphere microorganisms by secondary metabolite secretion and its immune system. Meanwhile, phyllosphere microorganisms play an important role in ecological stability and environmental safety assessment. However, as a result of the instability of the phyllosphere environment and the poor cultivability of phyllosphere microorganisms in the current research, there are still many limitations, such as the lack of insight into the mechanisms of plant-microorganism interactions, the roles of phyllosphere microorganisms in plant growth processes, the responses of phyllosphere microorganisms to plant metabolites, etc. This review summarizes the latest progress made in the research of the phyllosphere in recent years. This is beneficial for deepening our understanding of phyllosphere microorganisms and promoting the research of plant-atmosphere interactions, plant pathogens, and plant biological control.

S-metolachlor (S-ME) is a widely used chiral herbicide that can cause potential ecological risks via long-term usage. In this work, we chose a model plant, wheat, as the test material to determine the effects of applying 10 mg/kg S-ME to soil on its fresh weight, chlorophyll and malondialdehyde (MDA) content, and superoxide dismutase (SOD) activity and the diversity and structural composition of the phyllosphere microorganisms after 7 and 14 days of exposure. Our work showed that this concentration of residual S-ME in soil only slightly decreased plant biomass and had little effect on lipid peroxidation, the antioxidant enzyme system and chlorophyll content. Interestingly, although the test concentration of S-ME did not exert strong inhibitory effects on the physiological activities of wheat, it decreased the diversity of phyllosphere microbial communities and changed their structure, indicating that microorganisms were more sensitive stress indicators. S-ME reduced the colonization by some beneficial bacteria related to plant nitrogen fixation among the phyllosphere microorganisms, which influenced the growth and yield of wheat because these bacteria contribute to plant fitness. In addition, S-ME affected the association between the host and the composition of the phyllosphere microbial communities under different growth conditions. Our work provides insights into the ecological implications of the effects of herbicides on the phyllosphere microbiome. Unlabelled Image • S-ME can affect the phyllosphere microbiome of wheat. • The phyllosphere microbes are sensitive indicators of plant stress. • S-ME reduced the colonization by bacteria related to plant nitrogen fixation. [ABSTRACT FROM AUTHOR]

The characteristics of particles and microorganisms on leaf surfaces have great significance for the near-surface environment and ecology. Here, fresh leaves of holly and Ligustrum were examined from different functional areas in Qingdao. Environmental scanning electron microscopy was used to observe particles and microorganisms on the leaf surfaces during different seasonal, and Illumina high-throughput sequencing was performed to analyze the phyllosphere bacterial community structure. The results showed that the retention of TSP on leaves in autumn and winter was higher than in spring and summer. The leaves of the two plants were more likely to retain PM 10 and PM 2.5 ; however, the dust retention capacity of holly leaves was higher than that of Ligustrum, especially for particle sizes greater than 10 μm. The numbers of particles on the leaf surfaces along an urban main road were higher than in two other locations, and were greatly affected by ground dust and automobile exhaust emissions. The community structure of phyllospheric microorganisms showed distinct seasonal variation, with different types of fungi, fungal spores, and mycelium observed on the leaf surfaces. Mycelium was more frequently detected on leathery leaves, and fungal spores with even folds were detected on the leaf epidermis of Ligustrum. The relative abundances of phyllospheric microorganisms were highest on leaves from an urban park, explained by a positive effect of humidity on growth. Significant differences in bacterial community abundance were observed between seasons. Specifically, bacterial abundance was highest in spring and lowest in summer. γ-Proteobacteria were the dominant bacteria, and the two plants shared a similar core microbial community. In addition, the phyllospheric bacterial community structure of leaves from urban arterial roads with ground dust pollution was significantly different from the leaves collected from other city areas. Our research results suggest a significant correlation between the leaf-surface particles and microbial community structure on representative plants in different areas of the city, which provides reference information for urban greening activities.

Rehmannia glutinosa, a perennial herbaceous species, belongs to the family Scrophularia-ceae. As a staple medicinal material, its tuberous roots are highly valued in traditional Chinese medicine. However, R. glutinosa suffers from serious consecutive monoculture problems in production, which leads to a decline in both productivity and quality. Phyllosphere bacteria, the most abundant component of phyllosphere microorganisms, play crucial roles in plant growth and health. Characterization of phyllosphere bacteria could provide new insights into the mechanisms of consecutive monoculture problems and their control measures. Meanwhile, the varied taxa could be served as an important indicator of consecutive monoculture problems. The barcoded pyrosequencing of 16S rDNA genes combined with a culture-dependent approach was applied to characterize the shifts of bacterial community structure and diversity in the phyllosphere under consecutive monoculture of R. glutinosa. The results showed that consecutive monoculture clearly affected bacterial community structure in the phyllosphere. The phyllosphere bacterial communities of the two-year monocultured (TY) and the diseased plants (DP) were more similar, and different from the one-year monocultured (OY). The evenness, Shannon and Simpson diversity indices were significantly lower in TY and DP than in OY. Species annotation showed that bacterial community in R. glutinosa phyllosphere mainly consisted of Proteobacteria (91.2%), Firmicutes (5.1%) and Actinobacteria (3.7%). There was no significant difference in the number of detected bacterial taxa. However, Proteobacteria was significantly increased while Firmicutes and Actinobacteria were significantly decreased under consecutive monoculture. At the genus level, the relative abundances of genera Exiguobacterium, Bacillus and Arthrobacter, potentially beneficial microorganisms, were significantly higher in OY than that in TY and DP, but it was opposite for the genus Pseudomonas. The results from the culture-dependent approach and pathogenicity test showed that Pseudomonas plecoglossicida D9, widely isolated from the diseased leaves, was highly pathogenic to leaves. In conclusion, R. glutinosa monoculture resulted in distinct phyllosphere bacterial community variation with the accumulation of pathogen loads at the expense of beneficial microorganisms, which could contribute to the occurrence of leaf disease symptoms,and aggravate R. glutinosa replant disease in a monoculture regime.