Effects of Soil Conditioner (Volcanic Ash) on Yield Quality and Rhizosphere Soil Characteristics of Melon.

In this study, the effects of soil conditioners on the growth and development of melons and the rhizosphere soil environment were explored. The optimal amount of added soil conditioner was screened to solve the practical production problems of high-quality and high-yield thin-skinned melon. The melon variety "Da Shetou" was used as the material. Under the conditions of conventional fertilization and cultivation technology management, different soil conditioners were set up for potted melons. The effects of Pastoral soil (CK), 95% Pastoral soil + 5% volcanic ash soil conditioner (KT1), 85% Pastoral soil + 15% volcanic ash soil conditioner (KT2), 75% Pastoral soil + 25% volcanic ash soil conditioner (KT3), 65% Pastoral soil + 35% volcanic ash soil conditioner (KT4), and 55% Pastoral soil + 45% volcanic ash soil conditioner (KT5) on melon yield, quality, and rhizosphere soil characteristics were investigated. The soil microbial community was analyzed using Illumina MiSeq technology. Compared to CK, KT1, KT3, KT4, and KT5, the KT2 treatment could improve the single fruit yield of melon, increasing it by 4.35%, 2.48%, 2.31%, 5.92%, and 2.92%. Meanwhile, the highest contents of soluble protein, soluble solid, and soluble sugar in the KT2 treatment were 1.89 mg·100 g-1, 16.35%, and 46.44 mg·g-1, which were significantly higher than those in the control treatment. The contents of organic matter, total nitrogen, alkali-soluble nitrogen, nitrate nitrogen, ammonium nitrogen, available potassium, and available phosphorus in melon rhizosphere soil were the highest in the KT2 treatment. Through Alpha diversity analysis, it was found that the Chao1 index, Shannon index, and ACE index were significantly higher in the KT1 treatment than in the control, while, among all groups, the Simpson index and coverage were not significantly different. The dominant bacteria in the six treated samples were mainly Actinobacteriota, Proteobacteria, Cyanobacteria, Chloroflexi, Acidobacteria, Bacteroidetes, Myxomycota, Firmicutes, Gemmatimonadota, Verrucomicrobia, and Planctomycetes, which accounted for 96.59~97.63% of the relative abundance of all bacterial groups. Through redundancy analysis (RDA), it was found that the organic matter, electrical conductivity, available phosphorus, and nitrate nitrogen of melon rhizosphere soil were the dominant factors of bacterial community change at the dominant genus level. In summary, 15% ash soil conditioner applied on melon was the selected treatment to provide a theoretical reference for the application of soil conditioner in facility cultivation.

Impact of three exogenous phosphorus-solubilizing bacteria on zinc and selenium contents and rhizosphere soil nutrients of Longjing and Huangjinya tea plants.

Phosphate-solubilizing bacteria (PSB) enhance plant phosphorus utilization through their ability to dissolve phosphorus. To address the low utilization of nitrogen, phosphorus, potassium, zinc, and selenium by tea plants in acidic, selenium-rich soils, the study aimed to investigate the impact of exogenous PSB on soil nutrients and the absorption of zinc and selenium by tea plants. Following the inoculation of potted Longjing and Huangjinya varieties with exogenous phosphorus-solubilizing bacteria, we determined the concentrations of AN, AP, AK, Zn, and Se in their rhizosphere soil, in addition to the Zn and Se contents in their aboveground and belowground parts. The results show that after respective treatment with the three PSB, the concentration of available P in the tea plant rhizosphere soil significantly increased, with PMS08 having the most pronounced effect.After the same treatment, In the rhizosphere soil of Longjing tea plants, the AN content increased by 26.47%, 18.41%, and 7.51%, respectively, relative to the control, while the AK content decreased in the rhizosphere soil of Huangjinya tea plants. Inoculation with the three PSB resulted in a greater content of available Se in both the aboveground and belowground parts of the two tea plants. After inoculation with PMS20, the available Zn content of the belowground parts of Longjing and Huangjinya tea plants respectively decreased by 13.42% and 15.69% in comparison with the control. Additionally, after inoculating Longjing tea plants with PSt09 and Huangjinya tea plants with PMS08, the content of available Zn in their belowground parts significantly decreased by 9.22% and 35.74%, respectively. Evidently, the inoculation with the three phosphorus-solubilizing bacteria is beneficial for the uptake of available P by tea plants, promoting the utilization and accumulation of available Se. However, the content of AN or AK in rhizosphere soil varies between different tea plant varieties inoculated with the same kind of phosphorus-solubilizing bacteria. Moreover, the content of available Zn in tea plants also differs, highlighting the need to further investigate the differential effects of phosphorus-solubilizing bacteria on different plant varieties.

Recruitment and Aggregation Capacity of Tea Trees to Rhizosphere Soil Characteristic Bacteria Affects the Quality of Tea Leaves.

There are obvious differences in quality between different varieties of the same plant, and it is not clear whether they can be effectively distinguished from each other from a bacterial point of view. In this study, 44 tea tree varieties (Camellia sinensis) were used to analyze the rhizosphere soil bacterial community using high-throughput sequencing technology, and five types of machine deep learning were used for modeling to obtain characteristic microorganisms that can effectively differentiate different varieties, and validation was performed. The relationship between characteristic microorganisms, soil nutrient transformation, and tea quality formation was further analyzed. It was found that 44 tea tree varieties were classified into two groups (group A and group B) and the characteristic bacteria that distinguished them came from 23 genera. Secondly, the content of rhizosphere soil available nutrients (available nitrogen, available phosphorus, and available potassium) and tea quality indexes (tea polyphenols, theanine, and caffeine) was significantly higher in group A than in group B. The classification result based on both was consistent with the above bacteria. This study provides a new insight and research methodology into the main reasons for the formation of quality differences among different varieties of the same plant.

Nano- and Microplastics Increase the Occurrence of Bacterial Wilt in Tomato (Solanum lycopersicum L.).

Concern over nano- and microplastic contamination of terrestrial ecosystems has been increasing. However, little is known about the effect of nano- and microplastics on the response of terrestrial ecosystems already under biotic stress. Here, nano- and microplastics at 150-500 mg·kg-1 were exposed to tomatoes (Solanum lycopersicum L.), and the results demonstrate that the presence of nano- and microplastics increased the occurrence of bacterial wilt caused by Ralstonia solanacearum in tomatoes as a function of contaminant concentration, surface modification, and size. Our work shows that nanoplastics (30 nm, 250 mg·kg-1) increased the disease incidence by 2.19-fold. The disease severities in amino- and carboxyl-modified nanoplastic treatments were 30.4 and 21.7% higher than that in unmodified nanoplastic treatment, respectively. The severity of disease under the influence of different-sized nano- and microplastic treatments followed the order 30 > 100 nm > 1 > 50 µm. Mechanistically, nanoplastics disrupted the structure of the tomato rhizosphere soil bacterial community and suppressed the induced systemic resistance in tomato; nanoplastics in planta decreased the salicylic acid and jasmonic acid content in tomatoes, thus inhibiting systemic acquired resistance; and microplastics increased the soil water retention, leading to increased pathogen abundance in the rhizosphere. Additionally, the leachates from nano- and microplastics had no effect on disease occurrence or the growth of tomatoes. Our findings highlight a potential risk of nano- and microplastic contamination to agriculture sustainability and food security.

Genetic control of rhizosphere microbiome of the cotton plants under field conditions.

Understanding the extent of heritability of a plant-associated microbiome (phytobiome) is critically important for exploitation of phytobiomes in agriculture. Two crosses were made between pairs of cotton cultivars (Z2 and J11, L1 and Z49) with differential resistance to Verticillium wilt. F2 plants were grown in a field, together with the four parents to study the heritability of cotton rhizosphere microbiome. Amplicon sequencing was used to profile bacterial and fungal communities in the rhizosphere. F2 offspring plants of both crosses had higher average alpha diversity indices than the two parents; parents differed significantly from F2 offspring in Bray-Curtis beta diversity indices as well. Two types of data were used to study the heritability of rhizosphere microbiome: principal components (PCs) and individual top microbial operational taxonomic units (OTUs). For the L1 × Z49 cross, the variance among the F2 progeny genotypes (namely, genetic variance, VT) was significantly greater than the random variability (VE) for 12 and 34 out of top 100 fungal and bacterial PCs, respectively. For the Z2 × J11 cross, the corresponding values were 10 and 20 PCs. For 29 fungal OTUs and 10 bacterial OTUs out of the most abundant 100 OTUs, genetic variance (VT) was significantly greater than VE for the L1 × Z49 cross; the corresponding values for the Z2 × J11 cross were 24 and one. The estimated heritability was mostly in the range of 40% to 60%. These results suggested the existence of genetic control of polygenic nature for specific components of rhizosphere microbiome in cotton. KEY POINTS: • F2 offspring cotton plants differed significantly from parents in rhizosphere microbial diversity. • Specific rhizosphere components are likely to be genetically controlled by plants. • Common PCs and specific microbial groups are significant genetic components between the two crosses.

High-throughput 16S rRNA gene-based amplicon sequencing reveals the functional divergence of halophilic bacterial communities in the Suaeda salsa root compartments on the eastern coast of China.

The rhizosphere environment of plants, which harbors halophilic bacterial communities, faces significant challenges in coping with environmental stressors, particularly saline soil properties. This study utilizes a high-throughput 16S rRNA gene-based amplicon sequencing to investigate the variations in bacterial community dynamics in rhizosphere soil (RH), root surface soil (RS), root endophytic bacteria (PE) compartments of Suaeda salsa roots, and adjoining soils (CK) across six locations along the eastern coast of China: Nantong (NT), Yancheng (YC), Dalian (DL), Tianjin (TJ), Dongying (DY), and Qingdao (QD), all characterized by chloride-type saline soil. Variations in the physicochemical properties of the RH compartment were also evaluated. The results revealed significant changes in pH, electrical conductivity, total salt content, and ion concentrations in RH samples from different locations. Notably, the NT location exhibited the highest alkalinity and nitrogen availability. The pH variations were linked to HCO3- accumulation in S. salsa roots, while salinity stress influenced soil pH through H+ discharge. Despite salinity stress, enzymatic activities such as catalase and urease were higher in soils from various locations. The diversity and richness of bacterial communities were higher in specific locations, with Proteobacteria dominating PE samples from the DL location. Additionally, Vibrio and Marinobacter were prevalent in RH samples. Significant correlations were found between soil pH, salinity, nutrient content, and the abundance and diversity of bacterial taxa in RH samples. Bioinformatics analysis revealed the prevalence of halophilic bacteria, such as Bacillus, Halomonas, and Streptomyces, with diverse metabolic functions, including amino acid and carbohydrate metabolisms. Essential genes, such as auxin response factor (ARF) and GTPase-encoding genes, were abundant in RH samples, suggesting adaptive strategies for harsh environments. Likewise, proline/betaine transport protein genes were enriched, indicating potential bioremediation mechanisms against high salt stress. These findings provide insight into the metabolic adaptations facilitating resilience in saline ecosystems and contribute to understanding the complex interplay between soil conditions, bacterial communities, and plant adaptation.

Straw application improved soil biological properties and the growth of rice plant under low water irrigation.

The application of organic amendments is one way to manage low water irrigation in paddy soils. In this 60-day greenhouse pot experiment involving paddy soil undergoing drying-rewetting cycles, we examined the effects of two organic amendments: azo-compost with a low carbon to phosphorus ratio (C:P) of 40 and rice straw with a high C:P ratio of 202. Both were applied at rates of 1.5% of soil weight (w/w). The investigation focused on changes in certain soil biochemical characteristics related to C and P in the rice rhizosphere, as well as rice plant characteristics. The irrigation regimes applied in this study included constant soil moisture in a waterlogged state (130% water holding capacity (WHC)), mild drying-rewetting (from 130 to 100% WHC), and severe drying-rewetting (from 130 to 70% WHC). The results indicated that the application of amendments was effective in severe drying-rewetting irrigation regimes on soil characteristics. Drying-rewetting decreased soil respiration rate (by 60%), microbial biomass carbon (by 70%), C:P ratio (by 12%), soil organic P (by 16%), shoot P concentration (by 7%), and rice shoot biomass (by 30%). However, organic amendments increased soil respiration rate (by 8 times), soil microbial biomass C (51%), total C (TC) (53%), dissolved organic carbon (3 times), soil available P (AP) (100%), soil organic P (63%), microbial biomass P (4.5 times), and shoot P concentration (21%). The highest significant correlation was observed between dissolved organic carbon and total C (r= 0.89**). Organic amendments also increased P uptake by the rice plant in the order: azo-compost > rice straw > control treatments, respectively, and eliminated the undesirable effect of mild drying-rewetting irrigation regime on rice plant biomass. Overall, using suitable organic amendments proves promising for enhancing soil properties and rice growth under drying-rewetting conditions, highlighting the interdependence of P and C biochemical changes in the rhizosphere during the rice vegetative stage.

Nano molybdenum trioxide-mediated enhancement of soybean yield through improvement of rhizosphere soil molybdenum bioavailability for nitrogen-fixing microbial recruitment.

Molybdenum (Mo) plays a pivotal role in the growth and nitrogen-fixing process of plants mediated by rhizobia. However, the influence of nano­molybdenum trioxide (MoO3NPs) on soybean growth, rhizosphere bioavailable Mo, and nitrogen-fixing microorganisms remains underexplored. Here, we report that compared with that of ionic Mo and bulk MoO3, the utilization of MoO3NPs (specifically NPs0.05 and NPs0.15) significantly boosted the available Mo content in the rhizosphere soil throughout the seedling (by 21.64 %-101.38 %), podding (by 54.44 %-68.89 %), and mature stage (by 34.41 %-to 45.71 %) of soybean growth. Furthermore, both NPs0.05 and NPs0.15 treatments maintained consistently higher levels of acid-extractable Mo, reducible Mo, and oxidizable Mo across these stages, which facilitated stable conversion and supply of bioavailable Mo. Within the rhizosphere soil, NPs0.05 and NPs0.15 treatments resulted in the highest relative abundance of Rhizobiales and Bradyrhizobium genera, and significantly promoted the colonization of nitrogen-fixing microorganisms, thereby increasing the content of nitrate nitrogen (NO3--N) by 8.69 % and 7.72 % and ammonium nitrogen (NH4+-N) by 44.75 % and 17.55 %, respectively. Ultimately, these effects together contributed to 107.17 % and 84.00 % increment in soybean yield by NPs0.05 and NPs0.15 treatments, respectively. In summary, our findings underscore the potential of employing MoO3NPs to promote plant growth and maintain soil nitrogen cycling, indicating distinct advantages of MoO3NPs over ionic Mo and bulk MoO3.

Drivers of the Sisrè berry plant [Synsepalum dulcificum (Schumach & Thonn.) Daniell] rhizosphere bacterial communities in Benin.

Each plant species has its own rhizobacteriome, whose activities determine both soil biological quality and plant growth. Little knowledge exists of the rhizosphere bacterial communities associated with opportunity crops with high economic potential such as Synsepalum dulcificum. Native to West Africa, this shrub is famous for its red berries representing the only natural source of miraculin, a glycoprotein, with sweetening properties, but also playing a role in the treatment of cancer and diabetes. This study aimed to characterize the structure and diversity of rhizobacterial communities associated with S. dulcificum and to identify the parameters determining this diversity. An initial sampling stage allowed the collection of rhizosphere soils from 29 S. dulcificum accessions, belonging to three distinct phenotypes, from 16 municipalities of Benin, located either on farms or in home gardens. The bacterial diversity of these rhizosphere soils was assessed by Illumina sequencing of the 16S rRNA gene after DNA extraction from these soils. Furthermore, an analysis of the physicochemical properties of these soils was carried out. All accessions combined, the most represented phylum appeared to be Actinobacteriota, with an average relative abundance of 43.5 %, followed by Proteobacteria (14.8 %), Firmicutes (14.3 %) and Chloroflexi (12.2 %), yet the relative abundance of dominant phyla varied significantly among accessions (p < 0.05). Plant phenotype, habitat, climate and soil physicochemical properties affected the bacterial communities, but our study pointed out that soil physicochemical parameters were the main driver of rhizobacterial communities' structure and diversity. Among them, the assimilable phosphorus, lead, potassium, arsenic and manganese contents, texture and cation exchange capacity of rhizosphere soils were the major determinants of the composition and diversity of rhizosphere bacterial communities. These results suggested the possibility of improving the growth conditions and productivity of S. dulcificum, by harnessing its associated bacteria of interest and better managing soil physicochemical properties.

Influence of Chrysanthemum morifolium-maize intercropping pattern on yield, quality, soil condition, and rhizosphere soil microbial communities of C. morifolium.

Introduction: Chrysanthemum morifolium Ramat. is a perennial herb in the Compositae family, often employed in traditional Chinese medicine due to its medicinal value. The planting of C. morifolium faces the challenges of continuous cropping, and intercropping is able to somewhat overcome the obstacles of continuous cropping. Methods: In our study, we designed two different C. morifolium-maize intercropping patterns, including C. morifolium-maize narrow-wide row planting (IS) and C. morifolium-maize middle row planting (IM). Compared with monoculture, the agronomic traits, yield, active ingredients, soil physicochemical properties, soil enzyme activities, and rhizosphere soil microbial communities of C. morifolium and maize were measured under the two C. morifolium-maize intercropping patterns. Results: The findings indicated that (1) Intercropping elevated the agronomic traits, yield, and active ingredients of C. morifolium, especially in C. morifolium-maize narrow-wide row planting pattern, which indicating that interspecific distance played an important role in intercropping system; (2) Intercropping enhanced soil physicochemical properties and enzyme activities of C. morifolium and maize; (3) Intercropping altered rhizosphere soil microbial communities of C. morifolium and maize, making microbial interrelationships more complex. (4) Intercropping could recruit a large number of beneficial microorganisms enrich in the soil, including Bacillus, Sphingomonas, Burkholderia-Caballeronia-Paraburkholderia, Chaetomium, and Ceratorhiza, which may increase the content of AN, NN, AvK, ExCa, AvCu, AvZn and other nutrients in soil and promoted the growth and quality of C. morifolium. Discussion: In summary, intercropping with maize could promote the accumulation of beneficial microorganisms in the soil, thus improving the overall growing environment, and finally realizing the growth and improvement of C. morifolium.

Potassium fertilizer promotes the thin-shelled Tartary buckwheat yield by delaying senescence and promoting grain filling.

The application rate of potassium fertilizer is closely related to the yield of crops. Thin-shelled Tartary buckwheat is a new variety of Tartary buckwheat with the advantages of thin shell and easy shelling. However, little is known about application rate of potassium fertilizer on the yield formation of thin-shelled Tartary buckwheat. This study aimed to clarify the effect of potassium fertilizer on the growth and yield of thin-shelled Tartary buckwheat. A field experiment to investigate the characteristics was conducted across two years using thin-shelled Tartary buckwheat (Miku 18) with four potassium fertilizer applications including 0 (no potassium fertilizer, CK), 15 (low-concentration potassium fertilizer, LK), 30 (medium-concentration potassium fertilizer, MK), and 45 kg·ha-1 (high-concentration potassium fertilizer, HK). The maximum and average grain filling rates; starch synthase activity; superoxide dismutase and peroxidase activities in leaves; root morphological indices and activities; available nitrogen, phosphorus, and organic matter content in rhizosphere soil; urease and alkaline phosphatase activities in rhizosphere soil; plant height, main stem node number, main stem branch number, leaf number; grain number per plant, grain weight per plant, and 100-grain weight increased first and then decreased with the increase in potassium fertilizer application rate and reached the maximum at MK treatment. The content of malondialdehyde was significantly lower in MK treatment than in other three treatments. The yields of thin-shelled Tartary buckwheat treated with LK, MK, and HK were 1.22, 1.37, and 1.07 times that of CK, respectively. In summary, an appropriate potassium fertilizer treatment (30kg·ha-1) can delay the senescence, promote the grain filling, and increase the grain weight and final yield of thin-shelled Tartary buckwheat. This treatment is recommended to be used in production to achieve high-yield cultivation of thin-shelled Tartary buckwheat.

Assembly patterns and key taxa of bacterial communities in the rhizosphere soil of moso bamboo (Phyllostachys pubescens) under different Cd and Pb pollution.

Moso bamboo is excellent candidate for cadmium (Cd)/lead (Pb) phytoremediation, while rhizosphere microbiome has significant impact on phytoremediation efficiency of host plant. However, little is known about the rhizosphere bacterial communities of moso bamboo in Cd/Pb contaminated soils. Therefore, this study investigated the assembly patterns and key taxa of rhizosphere bacterial communities of moso bamboo in Cd/Pb polluted and unpolluted soils, by field sampling, chemical analysis, and 16S rRNA gene sequencing. The results indicated α-diversity between Cd/Pb polluted and unpolluted soils showed a similar pattern (p > 0.05), while ß-diversity was significantly different (p < 0.05). The relative abundance analysis indicated α-proteobacteria (37%) and actinobacteria (31%) were dominant in Cd/Pb polluted soils, while γ-proteobacteria (40%) and α-proteobacteria (22%) were dominant in unpolluted soils. Co-occurrence network analysis indicated microbial networks were less complex and more negative in polluted soils than in unpolluted soils. Mantel analysis indicated soil available phosphorus, organic matter, and available Pb were the most important environmental factors affecting microbial community structure. Correlation analysis showed 11 bacterial genera were significantly positively related to Cd/Pb. Overall, this study identified the bacterial community composition of bamboo rhizosphere in responding to Cd/Pb contamination and provides a theoretical basis for microbe-assistant phytoremediation in the future.

To date, little is known about the bacterial communities in the rhizosphere of moso bamboo under Cd and Pb multiple stresses. This study investigated the assembly patterns and key taxa of rhizospheric bacterial communities of moso bamboo in Cd/Pb polluted and unpolluted soils. It was found that the bacterial community structure in bamboo rhizosphere is easily influenced by soil chemical environment, such as fertilities and heavy metals. The key bacterial taxa identified here could be target microbe in future microbe-assistant phytoremediation.

Sinomonas terricola sp. nov., a plant-beneficial bacterium isolated from litchi rhizosphere soil in Guangdong, China.

A novel plant-beneficial bacterium strain, designated as JGH33T, which inhibited Peronophythora litchii sporangia germination, was isolated on Reasoner's 2A medium from a litchi rhizosphere soil sample collected in Gaozhou City, Guangdong Province, PR China. Cells of strain JGH33T were Gram-stain-positive, aerobic, non-motile, bent rods. The strain grew optimally at 30-37 °C and pH 6.0-8.0. Sequence similarity analysis based on 16S rRNA genes indicated that strain JGH33T exhibited highest sequence similarity to Sinomonas albida LC13T (99.2 %). The genomic DNA G+C content of the isolate was 69.1 mol%. The genome of JGH33T was 4.7 Mbp in size with the average nucleotide identity value of 83.45 % to the most related reference strains, which is lower than the species delineation threshold of 95 %. The digital DNA-DNA hybridization of the isolate resulted in a relatedness value of 24.9 % with its closest neighbour. The predominant respiratory quinone of JGH33T was MK-9(H2). The major fatty acids were C15 : 0 anteiso (43.4 %), C16 : 0 iso (19.1 %) and C17 : 0 anteiso (19.3 %), and the featured component was C18 : 3 ω6c (1.01 %). The polar lipid composition of strain JGH33T included diphosphatidylglycerol, phosphatidylglycerol, dimannosylglyceride, phosphatidylinositol and glycolipids. On the basis of polyphasic taxonomy analyses data, strain JGH33T represents a novel species of the genus Sinomonas, for which the name Sinomonas terricola sp. nov. is proposed, with JGH33T (=JCM 35868T=GDMCC 1.3730T) as the type strain.

Effects of short-term nitrogen and phosphorus addition on soil bacterial community of different halophytes.

Soil microbial community composition and diversity are often affected by nutrient enrichment, which may influence soil microbes to affect nutrient cycling and plant community structure. However, the response of soil bacteria to nitrogen (N) and phosphorus (P) addition and whether it is influenced by plants remains unclear. By 16S rRNA sequencing, we investigated the response of the rhizosphere and bulk soil bacterial communities of different halophytes (salt-rejecting, salt-absorbing, and salt-secreting plant) in the Yellow River Delta to short-term N and P addition. The response of rhizosphere bacterial diversity to N and P addition was opposite in Phragmites communis and Suaeda salsa. N addition increased the rhizosphere soil bacterial α-diversity of S. salsa and Aeluropus sinensis, while P addition decreased the rhizosphere bacterial α-diversity bacteria of S. salsa. The N and P addition had a weak effect on the rhizosphere bacterial community composition and a significant effect on the bulk soil bacterial community composition of halophytes. The S. salsa and P. communis bulk soil bacterial community were mainly influenced by P addition, while it was influenced by N addition in A. sinensis. N and P addition reduced the difference in bacterial community composition between the two types of soil. N and P addition increased the eutrophic taxa (Proteobacteria and Bacteroidetes) and decreased the oligotrophic taxa (Acidobacteria). Redundancy analysis showed that soil organic matter, salt, and total N content had significant effects on the bacterial community composition. The results clarify that the response of soil bacterial communities to N and P additions is inconsistent across the three halophyte soils, and the effect of plant species on the bacterial community was stronger than short-term N and P addition. IMPORTANCE: The bulk soil bacterial community was more affected by nutrient addition. Nitrogen (N) and phosphorus (P) have different effects on bacterial community. Soil organic matter is a key factor influencing the response of bacterial community to nutrient addition. N and P influence on bacterial community changes with plants.

Foliar Application of Nanoparticles Reduced Cadmium Content in Wheat (Triticum aestivum L.) Grains via Long-Distance "Leaf-Root-Microorganism" Regulation.

Foliar application of beneficial nanoparticles (NPs) exhibits potential in reducing cadmium (Cd) uptake in crops, necessitating a systematic understanding of their leaf-root-microorganism process for sustainable development of efficient nano-enabled agrochemicals. Herein, wheat grown in Cd-contaminated soil (5.23 mg/kg) was sprayed with different rates of four commonly used NPs, including nano selenium (SeNPs)/silica (SiO2NPs)/zinc oxide/manganese dioxide. SeNPs and SiO2NPs most effectively reduced the Cd concentration in wheat grains. Compared to the control, Cd concentration in grains was significantly decreased by 35.0 and 33.3% by applying 0.96 mg/plant SeNPs and 2.4 mg/plant SiO2NPs, and the grain yield was significantly increased by 33.9% with SeNPs application. Down-regulated gene expression of Cd transport proteins (TaNramp5 and TaLCT1) and up-regulated gene expression of vacuolar Cd fixation proteins (TaHMA3 and TaTM20) were observed with foliar SeNPs and SiO2NPs use. SeNPs increased the levels of leaf antioxidant metabolites. Additionally, foliar spray of SeNPs resulted in lower abundances of rhizosphere organic acids and reduced Cd bioavailability in rhizosphere soil, and soil microorganisms related to carbon and nitrogen (Solirubrobacter and Pedomicrobium) were promoted. Our findings underscore the potential of the foliar application of SeNPs and SiO2NPs as a plant and rhizosphere soil metabolism-regulating approach to reduce Cd accumulation in wheat grains.

Combined effects of azoxystrobin and oxytetracycline on rhizosphere microbiota of Arabidopsis thaliana.

The rhizosphere is one of the key determinants of plant health and productivity. Mixtures of pesticides are commonly used in intensified agriculture. However, the combined mechanisms underlying their impacts on soil microbiota remain unknown. The present study revealed that the rhizosphere microbiota was more sensitive to azoxystrobin and oxytetracycline, two commonly used pesticides, than was the microbiota present in bulk soil. Moreover, the rhizosphere microbiota enhanced network complexity and stability and increased carbohydrate metabolism and xenobiotic biodegradation as well as the expression of metabolic genes involved in defence against pesticide stress. Co-exposure to azoxystrobin and oxytetracycline had antagonistic effects on Arabidopsis thaliana growth and soil microbial variation by recruiting organic-degrading bacteria and regulating ABC transporters to reduce pesticide uptake. Our study explored the composition and function of soil microorganisms through amplicon sequencing and metagenomic approaches, providing comprehensive insights into the synergistic effect of plants and rhizosphere microbiota on pesticides and contributing to our understanding of the ecological risks associated with pesticide use.

Impacts of AlaAT3 transgenic poplar on rhizosphere soil chemical properties, enzyme activity, bacterial community, and metabolites under two nitrogen conditions.

Poplar stands as one of the primary afforestation trees globally. We successfully generated transgenic poplar trees characterized by enhanced biomass under identical nutrient conditions, through the overexpression of the pivotal nitrogen assimilation gene, pxAlaAT3. An environmental risk assessment was conducted for investigate the potential changes in rhizosphere soil associated with these overexpressing lines (OL). The results show that acid phosphatase activity was significantly altered under ammonium in OL compared to the wild-type control (WT), and a similar difference was observed for protease under nitrate. 16SrDNA sequencing indicated no significant divergence in rhizosphere soil microbial community diversity between WT and OL. Metabolomics analysis revealed that the OL caused minimal alterations in the metabolites of the rhizosphere soil, posing no potential harm to the environment. With these findings in mind, we anticipate that overexpressed plants will not adversely impact the surrounding soil environment.

Oerskovia flava sp. nov., a deoxynivalenol (DON)-degrading actinomycete isolated from the rhizosphere soil of long-term continuous cropping cucumber.

The deoxynivalenol (DON)-degrading bacterium JB1-3-2 T was isolated from a rhizosphere soil sample of cucumber collected from a greenhouse located in Zhenjiang, Eastern China. The JB1-3-2 T strain is a Gram-stain-positive, nonmotile and round actinomycete. Growth was observed at temperatures between 15 and 40 ℃ (optimum, 35 ℃), in the presence of 15% (w/v) NaCl (optimum, 3%), and at pH 3 and 11 (optimum, 7). The major cellular fatty acids identified were anteiso-C15:0, iso-C16:0 and anteiso-C17:0. Genome sequencing revealed a genome size of 4.11 Mb and a DNA G + C content of 72.5 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the JB1-3-2 T strain was most closely related to type strains of the Oerskovia species, with the highest sequence similarity to Oerskovia turbata NRRL B-8019 T (98.2%), and shared 98.1% sequence identity with other valid type strains of this genus. Digital DNA‒DNA hybridization (dDDH) and average nucleotide identity (ANI) showed 21.8-22.2% and 77.2-77.3% relatedness, respectively, between JB1-3-2 T and type strains of the genus Oerskovia. Based on genotypic, phylogenetic, chemotaxonomic, physiological and biochemical characterization, Oerskovia flava, a novel species in the genus Oerskovia, was proposed, and the type strain was JB1-3-2 T (= CGMCC 1.18555 T = JCM 35248 T). Additionally, this novel strain has a DON degradation ability that other species in the genus Oerskovia do not possess, and glutathione-S-transferase was speculated to be the key enzyme for strain JB1-3-2 T to degrade DON.

Analysis of Leaf and Soil Nutrients, Microorganisms and Metabolome in the Growth Period of Idesia polycarpa Maxim.

Idesia polycarpa Maxim is an emerging oil plant species. Understanding its microecological characteristics and internal mechanisms can serve as a basis for field management and the screening and application of growth-promoting bacteria during the growth phase of young trees. This study used three-year-old young I. polycarpa to analyze the tree's root morphology, soil, and leaf nutrient status variations from May to October. In addition, differences in the rhizosphere soil, leaf metabolites, and microorganisms were observed. The results showed that, from May to October, the total nitrogen (TN) in the soil significantly decreased, whereas the TN, total potassium (TK), and total phosphorus (TP) in the leaves differed (p < 0.05). The leaf-dominant bacteria changed from Pseudomonadota to Firmicutes phylum. In addition, the relative abundance of soil and leaf-dominant bacteria decreased. The study found that the soil and leaf differential metabolites were mainly sugars and phenolic acids. The soil bacterial community showed a significant correlation with soil pH, available potassium (AK), available phosphorus (AP), and TN (p < 0.05). Further, the soil fungal community was significantly correlated with pH and AK (p < 0.001). TP, pH, and TK were the main factors influencing the leaf bacterial community, while the leaf fungal community was significantly correlated with five factors, including pH, TC, and TN. The root morphology was also mainly affected by pH, Pedomicrobium sp., Talaromyces sp., Penicillium sp., and D-Mannitol 2.

The Combination of Biochar and Bacillus subtilis Biological Agent Reduced the Relative Abundance of Pathogenic Bacteria in the Rhizosphere Soil of Panax notoginseng.

In the continuous cropping of Panax notoginseng, the pathogenic fungi in the rhizosphere soil increased and infected the roots of Panax notoginseng, resulting in a decrease in yield. This is an urgent problem that needs to be solved in order to effectively overcome the obstacles associated with the continuous cropping of Panax notoginseng. Previous studies have shown that Bacillus subtilis inhibits pathogenic fungi in the rhizosphere of Panax notoginseng, but the inhibitory effect was not stable. Therefore, we hope to introduce biochar to help Bacillus subtilis colonize in soil. In the experiment, fields planted with Panax notoginseng for 5 years were renovated, and biochar was mixed in at the same time. The applied amount of biochar was set to four levels (B0, 10 kg·hm-2; B1, 80 kg·hm-2; B2, 110 kg·hm-2; B3, 140 kg·hm-2), and Bacillus subtilis biological agent was set to three levels (C1, 10 kg·hm-2; C2, 15 kg·hm-2; C3, 25 kg·hm-2). The full combination experiment and a blank control group (CK) were used. The experimental results show that the overall Ascomycota decreased by 0.86%~65.68% at the phylum level. Basidiomycota increased by -73.81%~138.47%, and Mortierellomycota increased by -51.27%~403.20%. At the genus level, Mortierella increased by -10.29%~855.44%, Fusarium decreased by 35.02%~86.79%, and Ilyonectria increased by -93.60%~680.62%. Fusarium mainly causes acute bacterial wilt root rot, while Ilyonectria mainly causes yellow rot. Under different treatments, the Shannon index increased by -6.77%~62.18%, the Chao1 index increased by -12.07%~95.77%, the Simpson index increased by -7.31%~14.98%, and the ACE index increased by -11.75%~96.12%. The good_coverage indices were all above 0.99. The results of a random forest analysis indicated that Ilyonectria, Pyrenochaeta, and Xenopolyscytalum were the top three most important species in the soil, with MeanDecreaseGini values of 2.70, 2.50, and 2.45, respectively. Fusarium, the primary pathogen of Panax notoginseng, ranked fifth, and its MeanDecreaseGini value was 2.28. The experimental results showed that the B2C2 treatment had the best inhibitory effect on Fusarium, and the relative abundance of Fusarium in Panax notoginseng rhizosphere soil decreased by 86.79% under B2C2 treatment; the B1C2 treatment had the best inhibitory effect on Ilyonectria, and the relative abundance of Ilyonectria in the Panax notoginseng rhizosphere soil decreased by 93.60% under B1C2 treatment. Therefore, if we want to improve the soil with acute Ralstonia solanacearum root rot, we should use the B2C2 treatment to improve the soil environment; if we want to improve the soil with yellow rot disease, we should use the B1C2 treatment to improve the soil environment.