Search

Microbial leftovers, known as necromass, are key players in storing carbon in the soil around plant roots (i.e. rhizosphere), a zone characterized by high‐efficiency microbial anabolism. Yet, the extent and mechanisms through which the rhizosphere contributes to soil organic carbon (SOC) via microbial necromass, especially under changing environments remain unclear. We aimed to evaluate the contributions of microbial necromass to SOC and influencing factors from the rhizosphere perspective. We collected the rhizosphere and bulk soil from 39 alpine coniferous forest sites on the eastern Tibetan Plateau to assess the extent of microbial necromass contribution to SOC in the rhizosphere from a dynamic perspective by calculating the ratio of increased amino sugars (AS) to increased SOC in the rhizosphere relative to that in bulk soil (RAS/SOC). We also collected climate data and determined nutrient concentrations and microbial physiological traits in rhizosphere soil to elucidate the factors affecting RAS/SOC. The results showed that across all sampling sites, the average concentrations of SOC‐normalized AS in the rhizosphere were significantly higher than those in the bulk soil. Furthermore, the average RAS/SOC was greater than 1, indicating a faster microbial necromass accumulation than SOC accumulation in the rhizosphere. These results implied that the rhizosphere sustains a greater capacity for microbial necromass contribution to the SOC pool than the bulk soil does. Soil nutrient availability was the primary factor affecting RAS/SOC, and precipitation indirectly affected microbial anabolism and RAS/SOC by changing soil nutrient status. Additionally, with increasing rhizosphere soil nutrient availability, microbial carbon‐use efficiency and growth rate increased but the biomass‐specific enzyme activity declined, indicating that microorganisms tended to exhibit high‐yield strategies with increasing soil nutrient availability. Synthesis. Our findings underpin the vital effect of microbial necromass in SOC accumulation from the rhizosphere perspective and offer valuable insights into mechanisms underlying microbial C metabolic processes in rhizosphere SOC accumulation under changing environments. [ABSTRACT FROM AUTHOR]

Background: In China, decline disease with unknown etiology appeared as an epidemic among bayberry trees in the southern area of the Yangtze River. Furthermore, the use of beneficial microbes has been reported to be able to reduce the incidence of this disease, emphasizing the association of this disease with microorganisms. Therefore, it has become critical to uncover the microbiome's function and related metabolites in remodeling the immunity of bayberry trees under biotic or abiotic stresses. Results: The amplicon sequencing data revealed that decline disease significantly altered bacterial and fungal communities, and their metabolites in the four distinct niches, especially in the rhizosphere soils and roots. Furthermore, the microbial communities in the four niches correlated with the metabolites of the corresponding niches of bayberry plants, and the fungal and bacterial networks of healthy trees were shown to be more complex than those of diseased trees. In addition, the role of microbiome in the resistance of bayberry trees to the occurrence of decline disease was justified by the isolation, identification, and characterization of important microorganisms such as significantly enriched Bacillus ASV804, Pseudomonas ASV815 in healthy plants, and significantly enriched Stenotrophomonas ASV719 in diseased plants. Conclusion: Overall, our study revealed that the occurrence of decline disease altered the microbiome and its metabolites in four ecological niches in particular rhizosphere soils and roots of bayberry, which provides new insight into the control of bayberry decline disease. [ABSTRACT FROM AUTHOR]

The intensive applications of nanomaterials in the agroecosystem led to the creation of several environmental problems. More efforts are needed to discover new insights in the nanomaterial–microbe–plant nexus. This relationship has several dimensions, which may include the transport of nanomaterials to different plant organs, the nanotoxicity to soil microbes and plants, and different possible regulations. This review focuses on the challenges and prospects of the nanomaterial–microbe–plant nexus under agroecosystem conditions. The previous nano-forms were selected in this study because of the rare, published articles on such nanomaterials. Under the study's nexus, more insights on the carbon nanodot–microbe–plant nexus were discussed along with the role of the new frontier in nano-tellurium–microbe nexus. Transport of nanomaterials to different plant organs under possible applications, and translocation of these nanoparticles besides their expected nanotoxicity to soil microbes will be also reported in the current study. Nanotoxicity to soil microbes and plants was investigated by taking account of morpho-physiological, molecular, and biochemical concerns. This study highlights the regulations of nanotoxicity with a focus on risk and challenges at the ecological level and their risks to human health, along with the scientific and organizational levels. This study opens many windows in such studies nexus which are needed in the near future. [ABSTRACT FROM AUTHOR]

Purpose: Soil quality is crucial for the growth and development of tea plants. Although the tea rhizosphere microbial composition and function have been extensively studied, few comparative studies have been performed to explore the different ecological niches of tea plants' microbes and their response to current global warming. Materials and methods: In this study, we selected a typical tea plant soil located in Chibi city, Hubei Province, China and collected samples during different seasons from rhizosphere and nonrhizosphere of tea plants. Using the Microbial phospholipid fatty acid analysis method and high-throughput sequencing to analyze the functions of dominant bacterial communities and strategies for coping with different environmental pressures. Results and discussion: The results showed that 19:0 cyclo ω7c was the dominant peak in both the rhizosphere and nonrhizosphere environments in winter compared with 16:0 in both the rhizosphere and nonrhizosphere soil in summer. The composition of PLFAs and a series of derived parameters were regulated by environmental factors such as soil pH, redox potential, total organic carbon, total nitrogen and NO3−-N content. In addition, the tea plant soil microorganisms differed significantly under the different temperature stresses, with significant enrichment of Ktedonobacteria and Micrococcaceae in winter and of Gammaproteobacteria and Proteobacteria in summer. Conclusions: The rhizosphere and nonrhizosphere soil microbial communities of tea plants were co-regulated by the root secretions growth conditions of tea plants, the fertilization conditions and the temperature stress. [ABSTRACT FROM AUTHOR]

Modulating the soil microbiome by applying microbial inoculants has gained increasing attention as eco-friendly option to improve soil disease suppressiveness. Currently, studies unraveling the interplay of inoculants, root-associated microbiome, and plant response are lacking for apple trees. Here, we provide insights into the ability of Bacillus velezensis FZB42 or Pseudomonas sp. RU47 to colonize apple root-associated microhabitats and to modulate their microbiome. We applied the two strains to apple plants grown in soils from the same site either affected by apple replant disease (ARD) or not (grass), screened their establishment by selective plating, and measured phytoalexins in roots 3, 16, and 28 days post inoculation (dpi). Sequencing of 16S rRNA gene and ITS fragments amplified from DNA extracted 28 dpi from different microhabitat samples revealed significant inoculation effects on fungal β-diversity in root-affected soil and rhizoplane. Interestingly, only in ARD soil, most abundant bacterial amplicon sequence variants (ASVs) changed significantly in relative abundance. Relative abundances of ASVs affiliated with Enterobacteriaceae were higher in rhizoplane of apple grown in ARD soil and reduced by both inoculants. Bacterial communities in the root endosphere were not affected by the inoculants but their presence was indicated. Interestingly and previously unobserved, apple plants responded to the inoculants with increased phytoalexin content in roots, more pronounced in grass than ARD soil. Altogether, our results indicate that FZB42 and RU47 were rhizosphere competent, modulated the root-associated microbiome, and were perceived by the apple plants, which could make them interesting candidates for an eco-friendly mitigation strategy of ARD. Key points: • Rhizosphere competent inoculants modulated the microbiome (mainly fungi) • Inoculants reduced relative abundance of Enterobacteriaceae in the ARD rhizoplane • Inoculants increased phytoalexin content in roots, stronger in grass than ARD soil [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhizal fungi play a key role in mediating soil–plant relationships within karst ecosystems. Sophora japonica, a medicinal plant with anti-inflammatory and antitumor properties, is widely cultivated in karst areas of Guangxi, China. We considered limestone, dolomite, and sandstone at altitudes ranging from 100 to 800 m and employed Illumina sequencing to evaluate AMF diversity and identify the factors driving S. japonica rhizosphere AMF community changes. We showed that the increase in altitude increased S. japonica AMF colonization and the Shannon index. The colonization of limestone plots was higher than that of other lithology. In total, 3,096,236 sequences and 5767 OTUs were identified in S. japonica rhizosphere soil. Among these, 270 OTUs were defined at the genus level and divided into 7 genera and 35 species. Moreover, available nitrogen, soil organic matter, and available calcium content had a coupling effect and positive influence on AMF colonization and Shannon and Chao1 indices. Conversely, available phosphorus, available potassium, and available magnesium negatively affected AMF Shannon and Chao1 indices. Lithology, altitude, pH, and available phosphorus are important factors that affect the dynamics of AMF in the S. japonica rhizosphere. [ABSTRACT FROM AUTHOR]

Plant health statesmay influence the distribution of rhizospheremicroorganisms, which regulate plant growth and development. In this study, the response of rhizosphere bacteria and fungi of healthy and diseased plants compared to bulk microbes was analyzed using high-throughput sequencing. Plant adaptation strategies of plants under potato virus Y (PVY) infection have been studied from a microbial perspective. The diversity and community structure of bacteria and fungi varied between bulk and rhizosphere soils, but not between healthy and diseased rhizosphere soils. A LEfSe analysis revealed the significant differences between different treatments on bacterial and fungal community compositions and identified Roseiflexaceae, Sphingomonas, and Sphingobium as the bacterial biomarkers of bulk (BCK), healthy rhizosphere (BHS), and diseased rhizosphere (BIS) soils, respectively; Rhodotorula and Ascomycota_unidentified_1_1 were identified as the fungal biomarkers of bulk (FCK) and healthy rhizosphere (FHS) soils. Bacterial networks were found to be more complex and compact than fungal networks and revealed the roles of biomarkers as network keystone taxa. PVY infection further increased the connectedness among microbial taxa to improve rhizosphere microbial community stability and resistance to environmental stress. Additionally, water content (WC) played an apparent influence on bacterial community structure and diversity, and pH showed significant effects on fungal community diversity. WC and pH greatly affected the biomarkers of bacterial rhizosphere communities, whereas the biomarkers of bulk bacterial communities were significantly affected by soil nutrients, especially for Sphingobium. Overall, the rhizosphere microbial community enrichment processes were different between healthy and diseased plants by changing the community compositions and identifying different biomarkers. These findings provide insight into the assemblage of rhizosphere microbial communities and soil physicochemical properties, which contributes to a deeper understanding of the establishment of an artificial core root microbiota to facilitate plant growth and bolstering resistance mechanisms. This knowledge contributes to a deeper understanding of the establishment of an artificial core root microbiota, thereby facilitating plant growth and bolstering resistance mechanisms. [ABSTRACT FROM AUTHOR]

Almost 95 % of all terrestrial plant species form symbioses with mycorrhizal fungi that mediate plant–soil interactions: mycorrhizae facilitate plant nitrogen (N) acquisition and are, therefore, vital for plant growth, but they also build a pathway for plant-assimilated carbon (C) into the rhizosphere. Therefore, mycorrhizae likely play an important role in shaping the response of ecosystems to environmental changes such as rising atmospheric carbon dioxide (CO2) concentrations, which can increase plant N demand and the transfer of plant C assimilation to the soil. While the importance of mycorrhizal fungi is widely recognised, they are rarely represented in current terrestrial biosphere models (TBMs) explicitly. Here, we present a novel, dynamic plant–mycorrhiza–soil model as part of the QUINCY (QUantifying Interactions between terrestrial Nutrient CYcles and the climate system) TBM. This new model is based on mycorrhizal functional types that either actively mine soil organic matter (SOM) for N or enhance soil microbial activity through increased transfer of labile C into the rhizosphere, thereby (passively) priming SOM decomposition. Using the Duke Free-Air CO2 Enrichment (FACE) experiment, we show that mycorrhizal fungi can have important effects on projected SOM turnover and plant nutrition under ambient as well as elevated- CO2 treatments. Specifically, we find that including enhanced active mining of SOM for N in the model allows one to more closely match the observations with respect to observed decadal responses of plant growth, plant N acquisition and soil C dynamics to elevated CO2 , whereas a simple enhancement of SOM turnover by increased below-ground C transfer of mycorrhizae is unable to replicate the observed responses. We provide an extensive parameter uncertainty study to investigate the robustness of our findings with respect to model parameters that cannot readily be constrained by observations. Our study points to the importance of implementing mycorrhizal functionalities in TBMs as well as to further observational needs to better constrain mycorrhizal models and to close the existing major knowledge gaps in actual mycorrhizal functioning. [ABSTRACT FROM AUTHOR]

Background: Plant growth-promoting rhizobacteria (PGPR) have a specific symbiotic relationship with plants and rhizosphere soil. The purpose of this study was to evaluate the effects of PGPR on blueberry plant growth, rhizospheric soil nutrients and the microbial community. Methods: In this study, nine PGPR strains, belonging to the genera Pseudomonas and Buttiauxella, were selected and added into the soil in which the blueberry cuttings were planted. All the physiological indexes of the cuttings and all rhizospheric soil element contents were determined on day 6 after the quartic root irrigation experiments were completed. The microbial diversity in the soil was determined using high-throughput amplicon sequencing technology. The correlations between phosphorus solubilization, the auxin production of PGPR strains, and the physiological indexes of blueberry plants, and the correlation between rhizospheric microbial diversity and soil element contents were determined using the Pearson's correlation, Kendall's tau correlation and Spearman's rank correlation analysis methods. Results: The branch number, leaf number, chlorophyllcontentand plant height of the treated blueberry group were significantly higher than those of the control group. The rhizospheric soil element contents also increased after PGPR root irrigation. The rhizospheric microbial community structure changed significantly under the PGPR of root irrigation. The dominant phyla, except Actinomycetota, in the soil samples had the greatest correlation with phosphorus solubilization and the auxin production of PGPR strains. The branch number, leaf number, and chlorophyllcontent had a positive correlation with the phosphorus solubilization and auxin production of PGPR strains and soil element contents. In conclusion, plant growth could be promoted by the root irrigation of PGPR to improve rhizospheric soil nutrients and the microenvironment, with modification of the rhizospheric soil microbial community. Discussion: Plant growth could be promoted by the root irrigation of PGPR to improve rhizospheric soil nutrients and the microenvironment, with the modification of the rhizospheric soil microbial community. These data may help us to better understand the positive effects of PGPR on blueberry growth and the rhizosphere soil microenvironment, as well as provide a research basis for the subsequent development of a rhizosphere-promoting microbial fertilizer. [ABSTRACT FROM AUTHOR]

Bell pepper farming significantly contributes to economic development in Abua. However, phyto-parasitic nematodes are endemic in the area and affect quality of crop yield. Hence, this study was undertaken to investigate the dynamics of occurrence of nematodes in bell pepper roots and soil samples of the farms in Abua. Roots and soil from the root rhizosphere were simultaneously collected at 0-20 cm depth using an improvised soil auger and knife. Modified sieve plate technique was employed for nematode detection and a pictorial key was used for nematode identification at the genera level. An overall nematode abundance of 746 nematodes in the soil around the root region and 216 nematodes in the root tissues of the bell peppers were recorded. Gracilachus species (10.6 %) was more prevalent in the soil, and Meloidogyne species (35.2 %) exhibited the highest population in roots. The study found that Abua's cultivated soil is susceptible to nematode infestation, limiting crop performance. The nematodes showcased root burrowing which is an inherent pattern for survival. The result on root nematodes across the five bell farms surveyed was not significant (p > 0.05). The result opined that farmers in Abua, Rivers State, should understand the role of the soil nematodes and implement soil improvement strategies for improved crop performance and rural economic development. [ABSTRACT FROM AUTHOR]

Soil samples were collected from research farm of Ebonyi State University and mining site in Izzi Local Government Area (L.G.A) of Ebonyi State. Rhizobacteria from rhizosphere of maize were identified using molecular methods. Tolerance of the isolates to heavy metals was assessed using standard laboratory techniques. The heavy metal profile of the soil was determined using atomic absorption spectrophotometer (AAS). Ability of the PGPB to remediate heavy metal polluted soil was assessed with hot plate aqua-regiae digestion method. The isolates were identified as: Pseudomonas fluorescens strain 5113, Alcaligenes faecalis strain P156, Pseudomonas syringae HS191, Bacillus subtilis strain NBSL51 and Bacillus cereus strain 20 UPMNR. P. fluorescens exhibited maximum tolerance at different concentrations of metals while A. faecalis had minimum tolerance. The heavy metal profile of the soil was determined and expressed in ppm as lead (25.0), copper (2.4), chromium (1.2) and zinc (16.0). The Isolates remediated the heavy metals. P. fluorescens + B. cereus maximally degraded the metals with values of (Pb = 87.2%, Zn = 69.25%, Cr =67.5%) while B. cereus alone degraded 70.0% Cu. P. fluorescens + B. cereus is recommended for soil that is contaminated with chromium, lead and zinc while B. cereus is recommended for copper contaminated soils. [ABSTRACT FROM AUTHOR]

The soil microbiome plays an important role in maintaining soil health, plant productivity, and soil ecosystem services. Current molecular-based studies have shed light on the fact that the soil microbiome has been quantitatively underestimated. In addition to metagenomic studies, metaproteomics and metatranscriptomic studies that target the functional part of the microbiome are becoming more common. These are important for a better understanding of the functional role of the microbiome and for deciphering plant-microbe interactions. Free-living beneficial bacteria that promote plant growth by colonizing plant roots are called plant growth-promoting rhizobacteria (PGPRs). They exert their beneficial effects in different ways, either by facilitating the uptake of nutrients and synthesizing particular compounds for plants or by preventing and protecting plants from diseases. A better understanding of plant-microbe interactions in both natural and agroecosystems will offer us a biotechnological tool for managing soil fertility and obtaining a high-yield food production system. [ABSTRACT FROM AUTHOR]

Aims: The proliferation of antibiotic resistance genes (ARGs) is a growing public health concern worldwide. Several studies have substantiated the significant role played by the plant microbiome in facilitating the transmission of antibiotic resistance, thereby posing a substantial threat to human health. However, the underlying mechanism of the transmission of antibiotic resistance from soil to plants is still largely unexplored. Methods: In the current study, we selected Sedum alfredii as a model plant to investigate the occurrence and distribution of ARGs across the soil–plant interface. Results: Our results showed that 20.34% of ARGs were significantly shifted between rhizosphere and bulk soils and were linked to distinct variations in bacterial functions across the soil-plant interface. Specifically, the ARGs enriched in the rhizosphere were significantly correlated to microbial functions of signaling pathways and degradation pathways. Conversely, the ARGs depleted in rhizosphere were significantly correlated to microbial functions of biosynthesis pathways, nutrient cycling, and ABC transport system. Moreover, our investigation involved metagenomic contig assembly, providing compelling evidence that these aforementioned relationships were indeed detected in the assembled bins. Conclusions: The results of our study revealed a clear association between the distribution of ARGs and changes in bacterial functions attributable to the assemblage of the rhizosphere microbiome at the soil-plant interface. These findings significantly contribute to enhancing our comprehension of the mechanism underlying the transmission of ARGs from bulk soils to rhizosphere soils. [ABSTRACT FROM AUTHOR]

The paper of van der Ent et al. (Plant Soil 485:247–257, 2023), published in the previous issue, reports the hyperaccumulation of rare earth elements (REE) in plant species from the Proteaceae for the first time. Indeed, the high REE accumulation in Proteaceae is not completely unexpected, given that the plants release large amounts of carboxylates to acquire phosphorus and micronutrients. However, it is somewhat questionable that the efficiency of element mobilization alone sufficiently explains the large variability in REE accumulation among different taxa of Proteaceae or other P-efficient species that typically show low concentrations of REE. Given that REE3+ share chemical similarities to Ca2+ but form stable complexes with ligands similar to Al3+, it is reasonable that uptake and accumulation of REE depend not solely on element mobility but also on the dynamics of element speciation governed by the formation, stability, and fate of carboxylate-REE-complexes in the rhizosheaths. The rationale behind this contention is that for elements with low mobility in soil, changes in chemical speciation may increase the availability only if the complex stabilities that depend on rhizosphere pH allow a breakdown during uptake. In this commentary, we explore the idea that REE accumulation depends on rhizosphere processes related to nutrient acquisition and element exclusion that overlap in time, space, and function depending on the composition of metal-chelating ligands released by plant roots in concert with rhizosphere pH. Based on data from greenhouse and field experiments, we propose a model where plants with a P-mining strategy (hyper)accumulate REE when rhizosphere pH is below a critical value shifting the REE speciation to available forms. [ABSTRACT FROM AUTHOR]

Background: Limited knowledge exists regarding the diversity of mangrove plant-associated Pseudarthrobacter species. This study presents the first draft genome and phylogenetic analysis of a Pseudarthrobacter oxydans NCCP-2145, isolated from the rhizospheric soil of Aviciana marina, a native mangrove plant found in Miani Hor, Lasbela-Baluchistan, Pakistan. Results: The genome of P. oxydans NCCP-2145 comprises 4,495,869 base pairs, with a G+C content of 65.9% and 4,207 coding sequences. Genome annotation revealed the presence of multiple biosynthesis pathways. The analysis also identified genes responsible for plant growth-promoting traits, such as the synthesis of indole acetic acid, nitrogen fixation, and phosphorus solubilization. Experimental evaluations confirmed strain NCCP-2145 positive reactions for phosphorus solubilization, indole-3-acetic acid production, and ammonia production. Furthermore, strain NCCP-2145 exhibited tolerance to heavy metals (nickel, copper, and cadmium) and salinity levels up to 10% NaCl. Antibiotic susceptibility testing indicated resistance only to ceftazidime and the combination of amoxicillin/clavulanic acid. For phylogenomic analysis, strain NCCP-2145 was analyzed and compared to the closely related validly published type species P. oxydans DSM 20119T, revealing a similarity score of 98.64% based on 16S rRNA gene sequences and 89.1% based on DNA-DNA hybridization, confirming its classification as a member of species, P. oxydans. Conclusions: This study significantly contributes to our understanding of the genomic characteristics, functional capabilities, and potential plant growth-promoting attributes of P. oxydans NCCP-2145. Future research should focus on unraveling the precise mechanisms underlying its plant growthpromoting abilities and exploring practical applications in sustainable agriculture and environmental restoration. [ABSTRACT FROM AUTHOR]

The Mediterranean area is one of the geographic zones most affected by land degradation and desertification and these conditions appear to be even more exacerbated by climate change. Based on this idea, this work aimed to isolate, identify, characterize, and select bacterial strains able to tolerate salinity and drought, which could possibly be used in agriculture as plant biofertilizers. The sampling of rhizosphere soil was performed in two Algerian regions, Ghardaïa and Djelfa (arid and semi-arid zones, respectively) in six provinces, targeting fourteen native plant species, known for their therapeutic use. A total of 288 bacterial strains were isolated, identified, and characterized for their growth at different temperatures and salt tolerance. Based on these capabilities, 95 isolates were selected. These strains underwent further evaluation for their plant-beneficial traits, including siderophore synthesis, auxin production, and phosphate solubilization. Additionally, we assessed their impact on tomato, cucumber, and sorghum seed germination. In a final screening step, nine bacterial strains were tested for their potential plant growth-promoting activity on tomato plants grown in semi-controlled conditions. Our results demonstrated that three strains (Bacillus simplex AH24, Microbacterium arborescens PU10, and Microbacterium paludicola AEA23) showed plant growth promotion activities on tomato. [ABSTRACT FROM AUTHOR]

Soil microbiota of the rhizosphere are an important extension of the plant phenotype because they impact the health and fitness of host plants. The composition of these communities is expected to differ among host plants due to influence by host genotype. Given that many plant populations exhibit fine‐scale genetic structure (SGS), associated microbial communities may also exhibit SGS. In this study, we tested this hypothesis using Chamaecrista fasciculata, a legume species that has previously been determined to have significant SGS. We collected genetic data from prokaryotic and fungal rhizosphere communities in association with 70 plants in an area of ~400 square meters to investigate the presence of SGS in microbial communities. Bacteria of Acidobacteria, Protobacteria, and Bacteroidetes and fungi of Basidiomycota, Ascomycota, and Mortierellomycota were dominant members of the rhizosphere. Although microbial alpha diversity did not differ significantly among plants hosts, we detected significant compositional differences among the microbial communities as well as isolation by distance. The strongest factor associated with microbial distance was genetic distance of the other microbial community, followed by geographic distance, but there was not a significant association with plant genetic distance for either microbial community. This study further demonstrates the strong potential for spatial structuring of soil microbial communities at the smallest spatial scales and provides further insight into the complexity of factors that influence microbial composition in soils and in association with host plants. [ABSTRACT FROM AUTHOR]

A metagenomic whole genome shotgun sequencing approach was used for rhizospheric soil micribiome of the wild plant Abutilon fruticosum in order to detect antibiotic resistance genes (ARGs) along with their antibiotic resistance mechanisms and to detect potential risk of these ARGs to human health upon transfer to clinical isolates. The study emphasized the potential risk to human health of such human pathogenic or commensal bacteria, being transferred via food chain or horizontally transferred to human clinical isolates. The top highly abundant rhizospheric soil non-redundant ARGs that are prevalent in bacterial human pathogens or colonizers (commensal) included mtrA, soxR, vanRO, golS, rbpA, kdpE, rpoB2, arr-1, efrA and ileS genes. Human pathogenic/colonizer bacteria existing in this soil rhizosphere included members of genera Mycobacterium, Vibrio, Klebsiella, Stenotrophomonas, Pseudomonas, Nocardia, Salmonella, Escherichia, Citrobacter, Serratia, Shigella, Cronobacter and Bifidobacterium. These bacteria belong to phyla Actinobacteria and Proteobacteria. The most highly abundant resistance mechanisms included antibiotic efflux pump, antibiotic target alteration, antibiotic target protection and antibiotic inactivation. antimicrobial resistance (AMR) families of the resistance mechanism of antibiotic efflux pump included resistance-nodulation-cell division (RND) antibiotic efflux pump (for mtrA, soxR and golS genes), major facilitator superfamily (MFS) antibiotic efflux pump (for soxR gene), the two-component regulatory kdpDE system (for kdpE gene) and ATP-binding cassette (ABC) antibiotic efflux pump (for efrA gene). AMR families of the resistance mechanism of antibiotic target alteration included glycopeptide resistance gene cluster (for vanRO gene), rifamycin-resistant beta-subunit of RNA polymerase (for rpoB2 gene) and antibiotic-resistant isoleucyl-tRNA synthetase (for ileS gene). AMR families of the resistance mechanism of antibiotic target protection included bacterial RNA polymerase-binding protein (for RbpA gene), while those of the resistance mechanism of antibiotic inactivation included rifampin ADP-ribosyltransferase (for arr-1 gene). Better agricultural and food transport practices are required especially for edible plant parts or those used in folkloric medicine. Key points: Risk of transfer of rhizosphere resistome of A. fruticosum to human gut was explored The most common resistance mechanism in this resistome is antibiotic efflux pump Rhizobiome is a source of new antibiotics with feasible therapeutic interventions [ABSTRACT FROM AUTHOR]

Almost 95 % of all terrestrial plant species form symbioses with mycorrhizal fungi that mediate plant-soil interactions: Mycorrhizae facilitate plant nitrogen (N) acquisition and are therefore vital for plant growth, but also build a pathway for plant-assimilated carbon (C) into the rhizosphere. Therefore, mycorrhizae likely play an important role in shaping the response of ecosystems to environmental changes such as rising atmospheric carbon dioxide (CO2) concentrations, which can increase plant N demand and the transfer of plant C assimilation to the soil. While the importance of mycorrhizal fungi is widely recognised, they are rarely represented in current terrestrial biosphere models (TBMs) explicitly. Here we present a novel, dynamic plant-mycorrhiza-soil model as part of the TBM QUINCY. This new model is based on mycorrhizal functional types that either actively mine soil organic matter (SOM) for N or enhance soil microbial activity though increased transfer of labile C into the rhizosphere and thereby (passively) prime SOM decomposition. Using the Duke Free-Air CO2 Enrichment (FACE) experiment, we show that mycorrhizal fungi can have important effects on projected SOM turnover and plant nutrition under ambient as well as elevated CO2 treatments. Specifically, we find that including enhanced active mining of SOM for N in the model allows to more closely match the observations with respect to observed decadal responses of plant growth, plant N acquisition, and soil C dynamics to elevated CO2, whereas a simple enhancement of SOM turnover by increased below-ground C transfer of mycorrhizae is unable to replicate the observed responses. We provide an extensive parameter uncertainty study to investigate the robustness of our findings with respect to model parameters that cannot readily be constrained by observations. Our study points to the importance of implementing mycorrhizal functionalities in TBMs as well as to further observational needs to better constrain mycorrhizal models and to close the existing major knowledge gaps of actual mycorrhizal functioning. [ABSTRACT FROM AUTHOR]

The aim of the research was to study the distribution of gallium (Ga) in rhizosphere soil and in plants growing under natural conditions in uncontaminated sites, with an emphasis on temporal fluctuations of Ga concentration in plants. For this purpose, two field experiments were conducted in St. Petersburg, Russia, in 2019 and 2020, at two sites. Three widespread grasses (couch grass, plantain, and dandelion) were chosen for the experiments. ICP–MS analytical technique was applied for the determination of Ga. All plants were capable of accumulating Ga, but the uptake of Ga was different in different plant species, although the plants grew under the same conditions. It can be assumed that one of the main reasons for such differences was the belonging of the plants to different botanical classes, where biochemical processes can proceed differently. The concentration of Ga in plants and rhizosphere soil varied in the daytime. The daily fluctuations of Ga in different plant species were often completely different and did not resemble the temporal fluctuations of Ga in rhizosphere soil. These short-term variations were due to natural reasons and should be considered when collecting plant and soil samples. [ABSTRACT FROM AUTHOR]

The rhizospheric soil of medicinal plants plays a vital role in influencing secondary metabolites and overall plant health. These fungi influence the content of bioactive chemicals and essential oils while also promoting plant growth. They improve the medicinal value and plant resistance to biotic and abiotic stressors as bioinoculants. The purpose of this review is to investigate the diversity of rhizosphere fungi in medicinal plants, recognize important fungal groups and recurring patterns, and comprehend how these fungi contribute to the diversity of above-ground plant life. These realizations may result in sustainable and environmentally favorable methods of managing medicinal plant cultivation. [ABSTRACT FROM AUTHOR]

Fertilization can be optimized and managed during the flue-cured tobacco growing period by studying the response of soil and microbial biomass stoichiometric characteristics to fertilization. In this study, we investigated the effect of compound fertilizers combined with microbial fertilizer treatments on the stoichiometric characteristics of the rhizosphere soil and the limitations of microbial resources during the flue-cured tobacco growing period. The results indicated that soil and microbial C:N:P varied greatly with the growing period. The effect of sampling time was usually greater than that of fertilization treatment, and microbial C:N:P did not vary with the soil resource stoichiometric ratio. The microbial metabolism of the tobacco-growing soil was limited by phosphorus after extending the growing period, and phosphorus limitation gradually increased from the root extension to the maturation periods but decreased at harvest. The rhizosphere soil microbial nitrogen and phosphorus limitations were mainly affected by soil water content, soil pH, microbial biomass carbon, and the ratio of microbial biomass carbon to microbial biomass phosphorus. Applying microbial fertilizer reduced phosphorus limitation. Therefore, applying microbial fertilizer regulated the limitation of microbial resources by affecting the soil and microbial biomass C:N:P in flue-cured tobacco rhizosphere soils. [ABSTRACT FROM AUTHOR]

Indigenous plants growing in mining spoils for phytoremediation have attracted great interest. To search the suitable plants, six plant species popular in the mine slag heaps of Gejiu City were collected and metal concentrations in plants and rhizosphere soils were analyzed. Results showed that the soils were greatly influenced by mine activities and heavy metal contents in plants were dependent upon those in the rhizosphere soils. However, the adaptation strategies varied among them. Bothriochloa ischcemum (Linn.) Keng and Equisetum ramosissimum Desf. had the Cr bioaccumulation factor (BAF) of 1.48 and 1.34, respectively, even though the rhizosphere soils were not contaminated by Cr. However, B. ischaemum and Agave americana Linn. showed the BAF for Pb, Zn Cu and Sn < 1.0, and Cyperus rotundus Linn. showed the similarly low BAF for Zn and Cu. Therefore, the three species had a great tolerance to phytostabilize these metals. Gymnema sylvestre (Retz.) Schult showed the translocation factor (TF) > 1.0 for Pb, Cu and Sn, so translocating these metals to the aboveground parts would be a feasible option. Similarly, Euphorbia cyathophora Murr. demonstrated the high phytotranslocate capacity for Cd and Sn, so it could be employed to remedy Cd and Sn-contaminated soils. This study investigated the phytoremediation potential of six indigenous plants widely growing on mine slag heaps in Gejiu, Yunnan. Bothriochloa ischcemum (Linn.) Keng and Equisetum ramosissimum Desf. were found to own a remarkable capacity to phytoaccumulate Cr. Bothriochloa ischaemum and Agave americana Linn. showed a great capacity to phytostabilize Pb, Zn Cu and Sn. Gymnema sylvestre (Retz.) Schult demonstrated the phytotransfer capacity for Pb, Cu and Sn, and Euphorbia cyathophora Murr. demonstrated the high phytotranslocate capacity for Cd and Sn. These findings will be useful to select suitable indigenous plants for the phytoremediation of local soils contaminated by mining activities. [ABSTRACT FROM AUTHOR]

Plant growth-promoting bacteria (PGPB) and other living organisms can help with the challenges of modern agriculture. PGPB offer ever-expanding possibilities for science and commerce, and the scientific results have been very advanced in recent years. In our current work, we collected the scientific results of recent years and the opinions of experts on the subject. Opinions and results on soil–plant relations, as well as the importance of PGPB and the latest related experiences, are important topics of our review work, which highlights the scientific results of the last 3–4 years. Overall, it can be concluded from all these observations that the bacteria that promote plant development are becoming more and more important in agriculture almost all over the world, thus, promoting more sustainable and environmentally conscious agricultural production and avoiding the use of artificial fertilizers and chemicals. Since many mechanisms of action, namely biochemical and operational processes, are still under investigation, a new emerging scientific direction is expected in the coming years with regard to PGPB, microbial, and other plant growth-stimulating substances, in which omics and microbial modulation also play a leading role. [ABSTRACT FROM AUTHOR]

Traditional oil mining poses negative effects on the environment through pollution with crude oil. One of the traditional mining sites in Wonocolo, Bojonegoro, Indonesia was reported to contaminate the surrounding area with a high level of crude oil. Therefore, this study aims to examine the microbiome profiles of contaminated soil and the rhizosphere of naturalized plants growing at the sites. It was conducted in Wonocolo, Bojonegoro to obtain an insight into the possible remediation efforts of using indigenous hydrocarbon-degrading bacteria and naturalized plants as in situ remediation agents. The results showed that the soil located close to the oil well-contained a high level of crude oil at 24.8%, and exhibited a distinct microbiome profile compared to those located further which had lower crude oil contamination of 14.15, 10.89, and 4.9%. Soil with the highest level of crude oil contamination had a comparatively higher relative abundance of assA, an anaerobic alkene-degrading gene. Meanwhile, the rhizosphere of the two naturalized plants, Muntingia calabura, and Pennisetum purpureum, exhibited indifferent microbiome profiles compared to the soil. They were found to contain less abundant hydrocarbon-degrading genes, such as C230, PAH-RHD-GP, nahAc, assA, and alkB suggesting that these naturalized plants might not be a suitable tool for in-situ remediation. This study provides information on the microbiome profile of soil and rhizosphere crude oil contaminated sites. The rhizosphere of growing plants in the crude-oil contaminated site exhibited a similar microbiome profile as in soil, with a lower relative abundance of hydrocarbon-degrading genes. Commonly, most inhabitant plants of the contaminated site have great potential as a phytoremediator agent, however, two largely abundant species were found to possess low potential. [ABSTRACT FROM AUTHOR]

[Objective] The microecological structure of blueberry rhizosphere soil was analyzed from the perspective of growth-promoting mi- croorganisms to improve the blueberry planting soil. 【Method】 The microbial community structure of blueberry rhizosphere soil was analyzed by high-throughput amplicon sequencing. The growth-promoting characteristics of culturable bacteria in blueberry rhizosphere were analyzed by selective medium and colorimetry. [Result] The relative abundance of 10 bacterial phyla and 3 fungal phyla was greater than 1%, and the relative abundance of 13 bacterial genera and 11 fungal genera was greater than 1%. Occallatibacter OTU6, Paraburkholderia OTU3, and Chujaibacter OTU945 represented the highest numbers of counts more than other bacterial OTU sequences. Pseudogymnoascus OTU1, Fusar- ium OTU7, and Lentinus OTU2 represented the highest numbers of counts more than other fungal OTU sequences. The growth-promoting characteristics analysis of culturable bacteria in blueberry rhizosphere soil showed that, 12 growth-promoting bacteria that could produce aux- in were screened from culturable bacteria in blueberry rhizosphere soil, and L7 strain had the highest auxin production. These 12 growth-pro- moting bacteria could grow on the phosphorus-solubilizing medium, and had significant phosphorus decomposition halos. Strain L42 had the strongest phosphorus-solubilizing capacity. Strain L11 and L17 could break down silicates. There was no inhibition between L17 strain and L21, L26, L37, L40, L41. But there was strong inhibition between L21 and L26, L40 strains. 16S rDNA sequencing results showed that, these strains were identified as Buttiauxella, Paraburkholderia and Pseudomonas. [Conclusion] The results indicated that the diversity of mi- crobial community structure in blueberry rhizosphere was significantly different from that of other economic crops, and the growth-promoting bacteria had good phosphorus-solubilizing effect and auxin production capacity, which could provide experimental basis for the subsequent development of blueberry rhizosphere microbial fertilizer. [ABSTRACT FROM AUTHOR]

【Objective】The microecological mechanism of tobacco root-knot nematode disease was clarified by studying the structure and diversity of fungal community in rhizosphere soil of diseased tobacco plants and healthy tobacco plants.【Method】Illumina MiSeq high-throughput sequencing was used to compare and analyze the fungal community structure and variation characteristics of soil nutrients in rhizosphere soil of diseased tobacco plants and healthy tobacco plants.【Result】The OUT abundance of fungi in rhizosphere soil of diseased plants and healthy tobacco plants were 1170 and 2120, respectively.The OUT abundance of fungi in healthy tobacco plants was 1.81 times higher than that of diseased plants, and the number of unique OTUs was 3.31 times higher than that of diseased plants; The Shannon, ACE and Chao1 indexes of rhizosphere soil of diseased plants decreased by 12.16%,52.96% and 50.40%,respectively.The relative abundance of M.sarnyensis, unclassified＿g＿Mortierella, unclassified＿k＿Fungi and unclassified＿ g＿ Penicillium in rhizosphere soil of diseased plants increased by 139.01%, 134.83%, 203.27% and 361.94%, respectively, compared with healthy tobacco plants, and all reached significant indigenous levels（P＜0.05）; The PCoA analysis of rhizosphere soil fungal community composition showed that there were significant differences between healthy tobacco plants and diseased tobacco plants; There was a certain correlation between the fungal community structure in rhizosphere soil of flue-cured tobacco and the change of soil nutrients, in which the soil pH was significantly negatively correlated with the common soil pathogen（Fusarium）, and the soil nutrients such as hydrolyzable nitrogen, available phosphorus and available potassium were significantly positively correlated with the beneficial soil microorganism（Mortierella）.【Conclusion】 The occurrence of tobacco root knot nematode disease significantly reduced the OUT abundance of fungi, and affected the distribution and relative abundance of the fungal community in rhizosphere soil of flue-cured tobacco. Rhizosphere soil fungal communities interact with soil nutrients and jointly affect the occurrence of tobacco root knot nematode disease. [ABSTRACT FROM AUTHOR]

Passion fruit (Passiflora edulis) is widely grown in tropical and subtropical regions, showing high economic and ornamental value. Microorganisms are indicators for the stability and health of the soil ecosystem, which can affect the yield and quality of passion fruit under continuous cropping. High-throughput sequencing and interactive analysis were used to analyse the variation of microbial communities in the noncultivated soil (NCS), cultivated soil (CS), and the rhizosphere soil of purple passion fruit (Passiflora edulis f. edulis ×Passiflora edulis f. flavicarpa, RP) and yellow passion fruit (Passiflora edulis f. flavicarpa, RY). An average of 98,001 high-quality fungal internal transcribed spacer (ITS) sequences, mainly from Ascomycota, Basidiomycota, Mortierellomycota, Mucoromycota and Glomeromycota, as well as an average of 71,299 high-quality bacterial 16S rRNA sequences, mainly from Proteobacteria, Actinobacteria, Acidobacteria, Firmicutes and Chloroflexi, were obtained per sample. It was found that the continuous cropping of passion fruit increased the richness but reduced the diversity of soil fungi, while it dramatically increased the richness and diversity of soil bacteria. In addition, during the continuous cropping, grafting different scions in the same rootstock contributed to the aggregation of differential rhizosphere microbial communities. Among fungal genera, Trichoderma showed higher abundance in RY than in RP and CS, while the opposite was observed in the pathogen Fusarium. Moreover, the co-occurrence network and potential function analyses also showed that the appearance of Trichoderma was related to Fusarium and its contribution to plant metabolism was significantly greater in RY than in RP and CS. In conclusion, the rhizosphere of yellow passion fruit may be beneficial for the enrichment of disease-resistant microbes, such as Trichoderma, which may be an important factor inducing stronger resistance to stem rot. It will help to form a potential strategy for overcoming the pathogen-mediated obstacles in passion fruit and improve its yield and quality. [ABSTRACT FROM AUTHOR]

[Objective] The study aimed to analyze the microbial diversity and community composition in the rhizospheric soil of the navel orange with citrus Huanglongbing to provide the new clue for ecological control of citrus Huanglongbing. [Method] The bacterial 16S rRNA region and fungal ITS region from the rhizosphere soils of diseased plants, healthy plants and bare land were sequenced and analyzed to evaluate the microbial community structure and diversity. Moreover, the physicochemical properties of four soil samples were also measured to determine the relationship between microbial community and soil physicochemical properties. [Result] The richness and diversity of bacterial community in rhizosphere soil of diseased plants were higher than that in the healthy plants, and the diversity of the fungal community in rhizosphere soil of diseased plants were also higher than that in the healthy plants, which the richness was lower than that of healthy plants. The microbial phyla found in diseased and healthy plants were similar on composition but significantly differed on relative abundance. Choroflexi and Acidobacteria had a higher abundance in the rhizosphere soil of diseased plants than that of healthy plants, whereas Actinobacteria and Basidiomycota had a lower abundance. At the genus level, the abundance of beneficial microorganisms, such as Bacillus and Talaromyces were lower in the rhizosphere soil of diseased plants than that of healthy plants, whereas the abundance of pathogen such as Fusarium and Aspergillus were higher. The contents of total phosphorus and total nitrogen were significantly lower in the rhizosphere soil of diseased plants than those of healthy plants, whereas the total carbon content was increased in diseased soil, and total phosphors had a significant impact on rhizosphere soil microbial community. [Conclusion] After navel oranges were infected with citrus Huanglongbing, the rhizosphere soil physical and chemical properties changed significantly, and the microbial diversity and community composition in rhizosphere soil of diseased plants also changed. To a certain extent, these differences reflect the effect of citrus Huanglongbing on the rhizosphere microecology of navel oranges. [ABSTRACT FROM AUTHOR]

Root exudates, as an important form of material input from plants to the soil, regulate the carbon input and efflux of plant rhizosphere soil and play an important role in maintaining the carbon and nutrient balance of the whole ecosystem. Root exudates are notoriously difficult to collect due to their underlying characteristics (e.g., low concentration and fast turnover rate) and the associated methodological challenges of accurately measuring root exudates in native soils. As a result, up until now, it has been difficult to accurately quantify the soil organic carbon input from root exudates to the soil in most studies. In recent years, the contribution and ecological effects of root exudates to soil organic carbon input and efflux have been paid more and more attention. However, the ecological mechanism of soil organic carbon input and efflux mediated by root exudates are rarely analyzed comprehensively. In this review, the main processes and influencing factors of soil organic carbon input and efflux mediated by root exudates are demonstrated. Soil minerals and soil microbes play key roles in the processes. The carbon allocation from plants to soil is influenced by the relationship between root exudates and root functional traits. Compared with the quantity of root exudates, the response of root exudate quality to environmental changes affects soil carbon function more. In the future, the contribution of root exudates in different plants to soil carbon turnover and their relationship with soil nutrient availability will be accurately quantified, which will be helpful to understand the mechanism of soil organic carbon sequestration. [ABSTRACT FROM AUTHOR]

Microbial communities in the rhizosphere influence nutrient acquisition and stress tolerance. How abiotic and biotic factors impact the plant microbiome in the wild has not been thoroughly addressed. We studied how plant genotype and soil affect the rhizosphere microbiome of Vaccinium floribundum, an endemic species of the Andean region that has not been domesticated or cultivated. Using high-throughput sequencing of the 16S rRNA and ITS region, we characterized 39 rhizosphere samples of V. floribundum from four plant genetic clusters in two soil regions from the Ecuadorian Highlands. Our results showed that Proteobacteria and Acidobacteria were the most abundant bacterial phyla and that fungal communities were not dominated by any specific taxa. Soil region was the main predictor for bacterial alpha diversity, phosphorous and lead being the most interesting edaphic factors explaining this diversity. The interaction of plant genotype and altitude was the most significant factor associated with fungal diversity. This study highlights how different factors govern the assembly of the rhizosphere microbiome of a wild plant. Bacterial communities depend more on the soil and its mineral content, while plant genetics influence the fungal community makeup. Our work illustrates plant–microbe associations and the drivers of their variation in a unique unexplored ecosystem from the Ecuadorian Andes. [ABSTRACT FROM AUTHOR]

Rhizosphere soil ecological functioning behavior is of critical importance for regulating phytoremediation efficiency during microbial-assisted phytoremediation for multi-heavy metal–polluted soils. In this study, Trifolium repens L. and its endophyte Pseudomonas putida were used to investigate the ecological responses of the microbe-plant-soil system in Cd, Cr, and Pb co-contaminated soil. The results showed that endophyte Pseudomonas putida significantly increased plant biomass by 22.26–22.78% and phytoremediation efficiency by 29.73–64.01%. The increased phytoremediation efficiency may be related to the improvement of photosynthetic pigment content and antioxidant enzyme activities in leaves and the enhancement of rhizosphere soil ecological functioning. With endophyte application, soil nutrient content was significantly increased and heavy metal bioavailability was enhanced that residual fraction was reduced by 3.79–12.87%. Besides, the relative abundance of ecologically beneficial rhizobacteria such as Bacteriovorax and Arthrobacter was increased by 3.04–8.53% and 0.80–1.64%, respectively. Endophyte inoculation also significantly increased all the functional genes involved in cellular processes, genetic information processing, environmental information processing, and metabolism. This study indicated that the application of endophytes has a positive effect on the biochemical responses of Trifolium repens L. and could significantly improve rhizosphere ecological functioning in multi-heavy metal contamination, which provided clear strategies for regulating phytoremediation. [ABSTRACT FROM AUTHOR]

Induced resistance (IR), a phenotypic state induced by an exogenous stimulus and characterized by enhanced resistance to future (a)biotic challenge, is an important component of plant immunity. Numerous IR-inducing stimuli have been described in various plant species, but relatively little is known about 'core' systemic responses shared by these distinct IR stimuli and the effects of IR on plant-associated microbiota. In this study, rice (Oryza sativa) leaves were treated with four distinct IR stimuli (β-aminobutyric acid, acibenzolar-S-methyl, dehydroascorbic acid, and piperonylic acid) capable of inducing systemic IR against the root-knot nematode Meloidogyne graminicola and evaluated their effect on the root transcriptome and exudome, and root-associated nematode communities. Our results reveal shared transcriptional responses—notably induction of jasmonic acid and phenylpropanoid metabolism—and shared alterations to the exudome that include increased amino acid, benzoate, and fatty acid exudation. In rice plants grown in soil from a rice field, IR stimuli significantly affected the composition of rhizosphere nematode communities 3 d after treatment, but by 14 d after treatment these changes had largely reverted. Notably, IR stimuli did not reduce nematode diversity, which suggests that IR might offer a sustainable option for managing plant-parasitic nematodes. [ABSTRACT FROM AUTHOR]

With the widespread use of abamectin in agriculture, there is increasing urgency to assess the effects of abamectin on soil microorganisms. Here, we treated plant-soil microcosms with abamectin at concentrations of 0.1 and 1.0 mg/kg and quantified the impacts of abamectin on bulk and rhizosphere soil microbial communities by shotgun metagenomics after 7 and 21 days of exposure. Although abamectin was reported to be easily degradable, it altered the composition of the soil microbial communities, disrupted microbial interactions, and decreased community complexity and stability after 7 days of exposure. After treatment with abamectin at a concentration of 1.0 mg/kg, some opportunistic human diseases, and soil-borne pathogens like Ralstonia were enriched in the soil. However, most ecological functions in soil, particularly the metabolic capacities of microorganisms, recovered within 21 days after abamectin treatment. The horizontal and vertical gene transfer under abamectin treatments increased the levels of antibiotic resistance genes dissemination. Overall, our findings demonstrated the negative effects of abamectin on soil ecosystems in the short-term and highlight a possible long-term risk to public and soil ecosystem health associated with antibiotic resistance genes dissemination. [ABSTRACT FROM AUTHOR]

Soil degradation remains an ongoing process that is exacerbated by the effects of climate change. Consequently, these processes decrease soil organic matter and nutrient contents, soil biological functions, and plant productivity. The addition of organic amendments (OAs) to the soil is a widespread practice to enhance soil quality and the health of agricultural soils. One of the most significant microbial hotspots controlling the processes, dynamics, and cycling of nutrients, carbon and water in terrestrial ecosystems is the rhizosphere. Understanding the continuing transformations of OAs and the distribution of different factors (C, nutrients, and microbial activities) across and along roots is crucial in the rhizosphere. The application of OAs to soil increases soil organic matter and nutrients, water holding capacity, improves soil structure and stimulates soil microbial activity and biomass. This review evaluates the role of the rhizosphere microbial community in organically amended soils for promoting plant growth and health. The diversity of the rhizosphere microbiome and the mechanisms used in plant protection are discussed. [ABSTRACT FROM AUTHOR]

Many petroleum extraction and refinement plants are located in arid climates. Therefore, the remediation of petroleum-polluted soils is complicated by the low moisture conditions. We ran a 70-day experiment to test the efficacy of various combining of remediation treatments with sorghum, yellow medick, and biochar to remove petroleum from and change the biological activity of Kastanozem, a soil typical of the dry steppes and semideserts of the temperate zone. At normal moisture, the maximum petroleum-degradation rate (40%) was obtained with sorghum–biochar. At low moisture, the petroleum-degradation rate was 22 and 30% with yellow medick alone and with yellow medick − sorghum, respectively. Biochar and the biochar-plant interaction had little effect on soil remediation. Both plants promoted the numbers of soil microbes in their rhizosphere: yellow medick promoted mostly hydrocarbon-oxidizing microorganisms, whereas sorghum promoted both hydrocarbon-oxidizing and total heterotrophic microorganisms. Low moisture did not limit microbial development. In the rhizosphere of sorghum, dehydrogenase and urease activities were maximal at normal moisture, whereas in the rhizosphere of yellow medick, they were maximal at low moisture. Peroxidase activity was promoted by the plants in unpolluted soil and was close to the control values in polluted soil. Biochar and the biochar-plant interaction did not noticeably affect the biological activity of the soil. [ABSTRACT FROM AUTHOR]

The rampant bayberry decline disease has been regarded as related to soil with the long-term plantation bayberry. These parameters, hydrogen, aluminum, other alkali cations, and plant-related nutrients, were measured from the soil around diseased tree roots 10, 20, and 30 years old. The pH significantly declined in topsoil with increasing tree age and rose with increasing depth of the soil layer with an age of 10, 20, and 30 years. The concentration of exchangeable aluminum has risen significantly with the increase of the tree ages in the top soil layer and also in 0 to 40 cm soils layer with ten-year-old trees. In the top soil layer with a depth of 0 to 10 cm, the cation concentrations of Ca2+, Mg2+, and K+ has fallen significantly with the increase of tree ages. A higher concentration of exchangeable aluminum was observed in the soil with trees more seriously affected by the disease and was accompanied with lower concentrations of Ca2+, Mg2+, and K+. The correlation analysis showed that the soil pH is significantly positively related to the concentration of exchangeable Ca2+, total nitrogen, and total phosphorus and negatively to exchangeable aluminum. These findings provided a new insight to mitigate the disease by regulating the soil parameters. [ABSTRACT FROM AUTHOR]

Nitrogen (N) application provides an effective way to enhance the efficiency of phosphorus (P) -phytoextraction. However, it remains unknown how N application facilitates P accumulation of P-accumulating plant by regulating rhizosphere P fractions. We investigated the P accumulation, rhizosphere P fractions and phosphatase activities of Polygonum hydropiper (P. hydropiper), a P-accumulating herb, across four growth periods in high-P soil (800 mg P kg−1) with different N applications (0 and 100 mg N kg−1). N application increased shoot P accumulation of P. hydropiper compared with the control, with the greatest shoot P accumulation in mining ecotype (ME) of P. hydropiper at 12 weeks. Compared with bulk soil, the concentration of H 2 O-Pi (Pi, inorganic P) and NaHCO 3 -P increased but the concentration of H 2 O-Po (Po, organic P) and NaOH-Po decreased in the rhizosphere after N application. Compared with the control, the stronger positive effects of NaHCO 3 -Po and HCl-Po on H 2 O-Pi and NaOH-Pi were observed after N application. The high activities of acid phosphomonoesterase (ACP) and alkaline phosphomonoesterase (ALP) in the rhizosphere of two ecotypes led to mineralization of Po. Overall, these results suggested that N application can enhance P-phytoextraction capability of P. hydropiper from high-P soil by increasing phosphatase activities and transforming P fractions. Our results also provided a practical optimization to extract excess P from high-P soil by P-accumulating plant. • N application enhanced P-phytoextraction efficiency of P. hydropiper. • ACP and ALP activities were increased by N application. • ACP and ALP activities promoted the mineralization of Po. • Po have stronger positive effects on H 2 O-Pi and NaOH-Pi under N application. [ABSTRACT FROM AUTHOR]

Background and Aims: While nitrogen (N) supply can enhance plant silicon (Si) accumulation, the mechanisms by which different forms of N affect Si mobilization in the rhizosphere are not well understood. This study aims to elucidate how pH changes induced by ammonium (NH4+) and nitrate (NO3−) affect Si availability in the rhizosphere, especially under low phosphorus (P) conditions.White lupin (Lupinus albus) plants were grown in non-fertilized low-P soil, supplied with a low dose of N, either as NH4+ or NO3−, with or without supply of monosilicic acid. We measured Si levels in various rhizosphere soil pools, along with different plant and rhizosphere soil parameters.The addition of NH4+ significantly lowered rhizosphere pH and decreased both Si adsorbed to pedogenic Fe/Mn oxides and amorphous phytogenic Si, resulting in higher concentrations of plant available Si in the white lupin rhizosphere. This led to greater Si uptake and improved plant growth compared to both the –N and + NO3− treatments. The supply of Si further enhanced these effects, with NH4+ showing a consistently different pattern of influence compared to NO3−. Additionally, –N white lupin plants accumulated more P than those treated with N, while Si supply significantly improved P acquisition across all treatments.Our study demonstrates that rhizosphere acidification induced by NH4+ nutrition can significantly enhance Si mobilization from the rhizosphere soil in the absence of Si supply and reduce Si adsorption when Si is applied. These findings may have practical implications for improving both Si mobilization in the rhizosphere and the effectiveness of Si fertilizers.Methods: While nitrogen (N) supply can enhance plant silicon (Si) accumulation, the mechanisms by which different forms of N affect Si mobilization in the rhizosphere are not well understood. This study aims to elucidate how pH changes induced by ammonium (NH4+) and nitrate (NO3−) affect Si availability in the rhizosphere, especially under low phosphorus (P) conditions.White lupin (Lupinus albus) plants were grown in non-fertilized low-P soil, supplied with a low dose of N, either as NH4+ or NO3−, with or without supply of monosilicic acid. We measured Si levels in various rhizosphere soil pools, along with different plant and rhizosphere soil parameters.The addition of NH4+ significantly lowered rhizosphere pH and decreased both Si adsorbed to pedogenic Fe/Mn oxides and amorphous phytogenic Si, resulting in higher concentrations of plant available Si in the white lupin rhizosphere. This led to greater Si uptake and improved plant growth compared to both the –N and + NO3− treatments. The supply of Si further enhanced these effects, with NH4+ showing a consistently different pattern of influence compared to NO3−. Additionally, –N white lupin plants accumulated more P than those treated with N, while Si supply significantly improved P acquisition across all treatments.Our study demonstrates that rhizosphere acidification induced by NH4+ nutrition can significantly enhance Si mobilization from the rhizosphere soil in the absence of Si supply and reduce Si adsorption when Si is applied. These findings may have practical implications for improving both Si mobilization in the rhizosphere and the effectiveness of Si fertilizers.Results: While nitrogen (N) supply can enhance plant silicon (Si) accumulation, the mechanisms by which different forms of N affect Si mobilization in the rhizosphere are not well understood. This study aims to elucidate how pH changes induced by ammonium (NH4+) and nitrate (NO3−) affect Si availability in the rhizosphere, especially under low phosphorus (P) conditions.White lupin (Lupinus albus) plants were grown in non-fertilized low-P soil, supplied with a low dose of N, either as NH4+ or NO3−, with or without supply of monosilicic acid. We measured Si levels in various rhizosphere soil pools, along with different plant and rhizosphere soil parameters.The addition of NH4+ significantly lowered rhizosphere pH and decreased both Si adsorbed to pedogenic Fe/Mn oxides and amorphous phytogenic Si, resulting in higher concentrations of plant available Si in the white lupin rhizosphere. This led to greater Si uptake and improved plant growth compared to both the –N and + NO3− treatments. The supply of Si further enhanced these effects, with NH4+ showing a consistently different pattern of influence compared to NO3−. Additionally, –N white lupin plants accumulated more P than those treated with N, while Si supply significantly improved P acquisition across all treatments.Our study demonstrates that rhizosphere acidification induced by NH4+ nutrition can significantly enhance Si mobilization from the rhizosphere soil in the absence of Si supply and reduce Si adsorption when Si is applied. These findings may have practical implications for improving both Si mobilization in the rhizosphere and the effectiveness of Si fertilizers.Conclusions: While nitrogen (N) supply can enhance plant silicon (Si) accumulation, the mechanisms by which different forms of N affect Si mobilization in the rhizosphere are not well understood. This study aims to elucidate how pH changes induced by ammonium (NH4+) and nitrate (NO3−) affect Si availability in the rhizosphere, especially under low phosphorus (P) conditions.White lupin (Lupinus albus) plants were grown in non-fertilized low-P soil, supplied with a low dose of N, either as NH4+ or NO3−, with or without supply of monosilicic acid. We measured Si levels in various rhizosphere soil pools, along with different plant and rhizosphere soil parameters.The addition of NH4+ significantly lowered rhizosphere pH and decreased both Si adsorbed to pedogenic Fe/Mn oxides and amorphous phytogenic Si, resulting in higher concentrations of plant available Si in the white lupin rhizosphere. This led to greater Si uptake and improved plant growth compared to both the –N and + NO3− treatments. The supply of Si further enhanced these effects, with NH4+ showing a consistently different pattern of influence compared to NO3−. Additionally, –N white lupin plants accumulated more P than those treated with N, while Si supply significantly improved P acquisition across all treatments.Our study demonstrates that rhizosphere acidification induced by NH4+ nutrition can significantly enhance Si mobilization from the rhizosphere soil in the absence of Si supply and reduce Si adsorption when Si is applied. These findings may have practical implications for improving both Si mobilization in the rhizosphere and the effectiveness of Si fertilizers. [ABSTRACT FROM AUTHOR]

Understanding the biological roles of root hairs is key to projecting their contributions to plant growth and to assess their relevance for plant breeding. The objective of this study was to assess the importance of root hairs for maize nutrition, carbon allocation and root gene expression in a field experiment. Applying wild type and root hairless rth3 maize grown on loam and sand, we examined the period of growth including 4-leaf, 9-leaf and tassel emergence stages, accompanied with a low precipitation rate. rth3 maize had lower shoot growth and lower total amounts of mineral nutrients than wild type, but the concentrations of mineral elements, root gene expression, or carbon allocation were largely unchanged. For these parameters, growth stage accounted for the main differences, followed by substrate. Substrate-related changes were pronounced during tassel emergence, where the concentrations of several elements in leaves as well as cell wall formation-related root gene expression and C allocation decreased. In conclusion, the presence of root hairs stimulated maize shoot growth and total nutrient uptake, but other parameters were more impacted by growth stage and soil texture. Further research should relate root hair functioning to the observed losses in maize productivity and growth efficiency. [ABSTRACT FROM AUTHOR]

Metal-induced oxidative stress in contaminated soils affects plant growth. In the present study, we evaluated the role of seed endophyte FXZ2 on Dysphania ambrosioides Zn/Cd tolerance and accumulation. A series of pot experiments were conducted under variable Zn (500, 1,000, and 1,500 mg kg-1) and Cd (5, 15, 30, and 60 mg kg-1). The results demonstrated that FXZ2-inoculation significantly enhanced the growth of D. ambrosioides and improved its chlorophyll and GSH content. In the rhizosphere, FXZ2 inoculation changed the chemical speciation of Zn/Cd and thus affected their uptake and accumulation in host plants. The exchangeable and carbonatebound fractions (F1 + F2) of Zn decreased in the rhizosphere of FXZ2-inoculated plants (E+) as compared to non-inoculated plants (E-) under Zn stress (500 and 1,000 mg kg-1), correspondingly, Zn in the shoots of E+ decreased (p < 0.05). However, at Cd stress (30 and 60 mg kg-1), the F1 + F2 fractions of Cd in E+ rhizospheric soils increased; subsequently, Cd in the shoots of E+ increased (p < 0.05). FXZ2 could exogenously secrete phytohormones IAA, GA, and JA. The study suggests that seed endophyte FXZ2 can increase Zn/Cd tolerance of host plant by altering Zn/Cd speciation in rhizospheric soils, as well as exogenous production of phytohormones to promote growth, lowering oxidative damage while enhancing antioxidant properties. For Zn/Cd accumulation, it has opposite effects: Zn uptake in E+ plants was significantly (p < 0.05) decreased, while Cd accumulation in E+ plants was significantly (p < 0.05) increased. Thus, FXZ2 has excellent application prospects in Cd phytoextraction and decreasing Zn toxicity in agriculturally important crops. [ABSTRACT FROM AUTHOR]

Rhizosphere microbial communities are recognized as crucial products of intimate interactions between plant and soil, playing important roles in plant growth and health. Enhancing the understanding of this process is a promising way to promote the next green revolution by applying the multifunctional benefits coming with rhizosphere microbiomes. In this study, we propagated eight cotton genotypes (four upland cotton cultivars and four sea-land cotton cultivars) with varying levels of resistance to Verticillium dahliae in three distinct soil types. Amplicon sequencing was applied to profile both bacterial and fungal communities in the rhizosphere of cotton. The results revealed that soil origin was the primary factor causing divergence in rhizosphere microbial community, with plant genotype playing a secondary role. The Shannon and Simpson indices revealed no significant differences in the rhizosphere microbial communities of Gossypium barbadense and G. hirsutum. Soil origin accounted for 34.0 and 59.05% of the total variability in the PCA of the rhizosphere bacterial and fungal communities, respectively, while plant genotypes within species only accounted for 1.1 to 6.6% of the total variability among microbial population. Similar results were observed in the Bray-Curtis indices. Interestingly, the relative abundance of Acidobacteria phylum in G. barbadense was greater in comparison with that of G. hirsutum. These findings suggested that soil origin and cotton genotype modulated microbiome assembly with soil predominantly shaping rhizosphere microbiome assembly, while host genotype slightly tuned this recruitment process by changing the abundance of specific microbial consortia. [ABSTRACT FROM AUTHOR]

Bacterial communities producing ectoine were studied in the rhizosphere of red goosefoot (Chenopodium rubrum L.) and weeping alkaligrass (Puccinellia distans (Jacq.) Parl.) growing on technogenic soil (Technosol) near the salt dump of the Solikamsk Potash Industrial Ore Administration 2 (SPIOA 2) of Uralkali PJSC (Solikamsk, Perm region) in order to assess the effect of this osmoprotective compound on plants under the conditions of technogenic salinization. It was found that most of bacteria in the studied soil are capable of synthesizing ectoine. The content of ectoine in the soil, as well as the number of producing bacteria, was higher in the rhizosphere than in the soil without plants. The concentration of ectoine was 167.4 ± 9.8 µmol/kg in the rhizosphere of red goosefoot, 92.9 ± 14.1 µmol/kg in the rhizosphere of weeping alkaligrass, and 23.9 ± 8.4 µmol/kg in the soil without plants. Bacteria belonging to the Pseudomonas genus predominated in the bacterial community of the rhizosphere of red goosefoot, and representatives of the Halomonas genus predominated in the rhizosphere of weeping alkaligrass. A stimulating effect on the growth of seedling roots under the conditions of salt stress was found for the following ectoine-producing strains: Halomonas sp. MK 2-1, Pseudomonas sp. BR 19-12, and Dietzia sp. PMK 9. The data obtained indicate the existence of positive effect of rhizosphere bacterial communities on plants under salinization due to the production of ectoine and may be used to develop biotechnologies that increase the productivity of plants growing on saline soils. [ABSTRACT FROM AUTHOR]

Background and aims: It is known that the single and combined use of phosphate-solubilizing bacteria (PSB) and silicon (Si) have the potential to improve the uptake of phosphorus (P) by plants in calcareous soils. However, it was unclear which form of Si in soil would have the most profound effects on the uptake of P by wheat plant inoculated with PSB. Here we investigated the effect of Si fertilizer on chemical forms of Si and P uptake by wheat plant inoculated with PSB in a calcareous soil. Determining different forms of Si in calcareous soils with a low P supply is essential to better understand the capacity of these forms to supply wheat plant with P in the presence of PSB. Methods: A pot trial in a completely randomized design with factorial arrangement in 3 repetitions under greenhouse conditions was adopted to investigate the effect of Si fertilizer alone or in combination with PSB on the uptake of P and Si by wheat plant grown on a calcareous soil with low available P. Experimental treatments included: Si factor at four levels of 0, 150, 300, and 600 mg Si kg−1 from silicic acid source and PSB strains factor at three levels of B0 (control), Pseudomonas sp. FA1, and Bacillus simplex UT1. The impacts of Si levels and PSB on shoot and root dry weight and the wheat shoot uptake of Si and P were measured. Also, the chemical forms of Si in wheat rhizosphere and non-rhizosphere soil and the regression models of the variables were studied to better understand the mechanisms of this process. Results: With increasing the levels of Si, the plant available Si with the lowest level, adsorbed Si, and amorphous Si with the highest level in both the rhizosphere and non-rhizosphere soil increased. In addition, Si fertilization-mediated increase at level of the soil Si fractions was intensified in the presence of PSB strains. The highest plant available Si (75.50 mg Si kg−1 soil) was obtained from the treatment of 600 mg Si kg−1 soil in the presence of Pseudomonas sp. FA1. The combined application of Si and PSB strains also increased the wheat shoot dry weight by 3.5 times compared to the control treatments. The use of Si alone at level of 300 mg Si kg−1 also increased the wheat shoot content of P by 2.3 times compared to the control treatment. However, the combined application of Pseudomonas sp. FA1 and Si at level of 600 mg Si kg−1 increased the wheat shoot content of P by 4 times compared to the control treatment. According to the correlations among the studied parameters, in addition to the expected positive correlation between plant available Si of wheat rhizosphere soil and the measured parameters, a positive and significant correlation between adsorbed Si of wheat rhizosphere soil and the shoot uptake of Si (r2 = 0.84, P < 0.01) and the shoot uptake of P (r2 = 0.58, P < 0.05) was also observed in this study. Conclusions: The information on the distribution of different forms of Si and the availability of P following the combined use of PSB strains and Si in this study (e.g., the role of rhizosphere adsorbed Si in increasing the wheat shoot uptake of P) may help in better management of P-fertilization in calcareous soils. [ABSTRACT FROM AUTHOR]

In order to study the relationships among rhizosphere microbial community, soil physicochemical properties, radioactivity and associated pollution, the rhizosphere soils of 7 dominant plants were collected from a decommissioned uranium mine. The soil physicochemical property analysis, Illumina high-throughput sequencing and redundancy analysis (RDA) were carried out. The results showed that the contents of arsenic, lead, cadmium, zinc and uranium in rhizosphere soil of most dominant plants were higher than the local background values. The top 10 bacterial phya in rhizosphere soil were Acidobacteriota, Actinobacteriota, Proteobacteria, unidentified&lowbar;Bacteria and Crenarchaeota, Chloroflexi, Firmicutes, Verrucomicrobiota, Bacteroidota, unidentifiedϣArchaea, with a total relative abundance 80.9%-89.0%. The top 10 fungi phyla were Mortierellomycota, Ascomycota, Basidiomycota, Mucoromycota, Chytridiomycota, Glomeromycota, Rozellomycota, Blastocladiomycota, Olpidiomycota, and Monoblepharomycota, with a total relative abundance 82.4%-96.5%. The growth of dominant plants improved the biodiversity of soil microorganisms, and specific microbial genera were enriched in the rhizosphere soil of certain plants. RDA analysis showed that chromium, arsenic and lead were the main driving factors affecting the dominant rhizosphere microbial community structure. The growth of dominant plants in mining areas increased the diversity of soil microorganisms and formed special symbionts with rhizosphere microorganisms to adapt to pollution. This study shows that symbionts composed of dominant plants and recruited microorganisms in contaminated areas have potential application in bioreremediation in the future. This study laid a theoretical foundation for the screening of biomaterials for plant-microbial combined remediation in the later stage. [ABSTRACT FROM AUTHOR]

Phytoremediation is an important solution to heavy metal pollution in soil. However, the impact of plants on microbial communities in contaminated soil also requires attention. Community-level physiological profiling (CLPP) based on the Biolog™ EcoPlate and high-throughput sequencing were used to study the soil microbial community in this article. The rhizosphere and bulk soil samples of six native species were collected from the iron mine tailings on Jiulong Mountain, Jiangxi Province. According to the average well color development (AWCD), all plants improved the activity and diversity of the contaminated soil microbial community to varying degrees. Cunninghamia lanceolate is considered to have good effects and led to the appearance of Cunninghamia lanceolata > Zelkova schneideriana > Toona ciliata > Alnus cremastogyne > Cyclobalanopsis myrsinifolia > Pinus elliottii. The Shannon–Wiener diversity index and principal component analysis (PCA) show that the evenness and dominance of soil microbial communities of several plants are structurally similar to those of uncontaminated soil (UNS). The results of high-throughput sequencing indicated that the bacterial community diversity of C. lanceolata, A. cremastogyne, and P. elliottii is similar to UNS, while fungal community diversity is different from UNS. C. lanceolata has a better effect on soil nutrients, C. myrsinifolia and P. elliottii may have a better effect on decreasing the Cu content. The objective of this study was to assess the influence of native plants on microbial communities in soils and the soil remediation capacity. Mortierellomycota was the key species for native plants to regulate Cu and microbial community functions. Native plants have decisive influence on microbial community diversity. [ABSTRACT FROM AUTHOR]

Background and aims: The Kiwifruit Vine Decline Syndrome (KVDS) is a disease that is currently a challenge for kiwifruit production in Italy, and it is spreading in new production areas. However, the causal agent of this syndrome has not been clearly identified, and we still know little about the overall effects of KVDS on the interactions between the host plant and its microbiome.In this study, we combined metabarcoding and targeted isolation (leaf baiting) to characterize the changes in the rhizosphere and root microbiomes associated with symptoms of KVDS.Our results suggest that KVDS has little impact on the bacterial, fungal, and oomycete communities associated with soil and roots, and we detected weak signatures of potential dysbiosis. On the other hand, we found a consistent association of the oomycete Phytopythium vexans with samples from plants symptomatic to KVDS, which matches the nucleotide sequences of the isolates obtained through baiting and, partially, the isolates from previous studies.While our results support the idea that P. vexans might be the major candidate agent of KVDS, there are still several unanswered questions that need to be addressed before being able to provide effective solutions to this emerging challenge in kiwifruit production.Methods: The Kiwifruit Vine Decline Syndrome (KVDS) is a disease that is currently a challenge for kiwifruit production in Italy, and it is spreading in new production areas. However, the causal agent of this syndrome has not been clearly identified, and we still know little about the overall effects of KVDS on the interactions between the host plant and its microbiome.In this study, we combined metabarcoding and targeted isolation (leaf baiting) to characterize the changes in the rhizosphere and root microbiomes associated with symptoms of KVDS.Our results suggest that KVDS has little impact on the bacterial, fungal, and oomycete communities associated with soil and roots, and we detected weak signatures of potential dysbiosis. On the other hand, we found a consistent association of the oomycete Phytopythium vexans with samples from plants symptomatic to KVDS, which matches the nucleotide sequences of the isolates obtained through baiting and, partially, the isolates from previous studies.While our results support the idea that P. vexans might be the major candidate agent of KVDS, there are still several unanswered questions that need to be addressed before being able to provide effective solutions to this emerging challenge in kiwifruit production.Results: The Kiwifruit Vine Decline Syndrome (KVDS) is a disease that is currently a challenge for kiwifruit production in Italy, and it is spreading in new production areas. However, the causal agent of this syndrome has not been clearly identified, and we still know little about the overall effects of KVDS on the interactions between the host plant and its microbiome.In this study, we combined metabarcoding and targeted isolation (leaf baiting) to characterize the changes in the rhizosphere and root microbiomes associated with symptoms of KVDS.Our results suggest that KVDS has little impact on the bacterial, fungal, and oomycete communities associated with soil and roots, and we detected weak signatures of potential dysbiosis. On the other hand, we found a consistent association of the oomycete Phytopythium vexans with samples from plants symptomatic to KVDS, which matches the nucleotide sequences of the isolates obtained through baiting and, partially, the isolates from previous studies.While our results support the idea that P. vexans might be the major candidate agent of KVDS, there are still several unanswered questions that need to be addressed before being able to provide effective solutions to this emerging challenge in kiwifruit production.Conclusion: The Kiwifruit Vine Decline Syndrome (KVDS) is a disease that is currently a challenge for kiwifruit production in Italy, and it is spreading in new production areas. However, the causal agent of this syndrome has not been clearly identified, and we still know little about the overall effects of KVDS on the interactions between the host plant and its microbiome.In this study, we combined metabarcoding and targeted isolation (leaf baiting) to characterize the changes in the rhizosphere and root microbiomes associated with symptoms of KVDS.Our results suggest that KVDS has little impact on the bacterial, fungal, and oomycete communities associated with soil and roots, and we detected weak signatures of potential dysbiosis. On the other hand, we found a consistent association of the oomycete Phytopythium vexans with samples from plants symptomatic to KVDS, which matches the nucleotide sequences of the isolates obtained through baiting and, partially, the isolates from previous studies.While our results support the idea that P. vexans might be the major candidate agent of KVDS, there are still several unanswered questions that need to be addressed before being able to provide effective solutions to this emerging challenge in kiwifruit production. [ABSTRACT FROM AUTHOR]