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.

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.

Integrated management of fruit trees and Bletilla striata: implications for soil nutrient profiles and microbial community structures

Introduction

Forest medicinal compound systems in agroforestry ecosystems represent a multi-layered cultivation approach that utilizes forest resources efficiently. However, research on how these systems affect soil nutrients and microbial communities is limited.

Methods

This study compared the soil chemical properties and microbial communities of Bletilla striata (C) grown alone versus in agroforestry systems with apple (PB), pear (LB), and peach trees (TB), aiming to understand the impact of these systems on soil health and microbial diversity.

Results

Soil in the GAB systems showed increased levels of essential nutrients but lower pH and ammonium nitrogen levels compared to the control. Significant improvements in organic matter, total phosphorus, and total potassium were observed in TB, PB, and LB systems, respectively. The bacterial diversity increased in GAB systems, with significant changes in microbial phyla indicative of a healthier soil ecosystem. The correlation between soil properties and bacterial communities was stronger than with fungal communities.

Discussion

Integrating B. striata with fruit trees enhances soil nutrients and microbial diversity but may lead to soil acidification. Adjustments such as using controlled-release fertilizers and soil amendments like lime could mitigate negative impacts, improving soil health in GAB systems.

The structure and diversity of bacteria and fungi in the roots and rhizosphere soil of three different species of Geodorum

Shepherd's crook (Geodorum) is a genus of protected orchids that are valuable both medicinally and ornamentally. Geodorum eulophioides (GE) is an endangered and narrowly distributed species, and Geodorum densiflorum (GD) and Geodorum attenuatum (GA) are widespread species. The growth of orchids depend on microorganisms. However, there are few studies on the microbial structure in Geodorum, and little is known about the roles of microorganisms in the endangered mechanism of G. eulophioides. This study analyzed the structure and composition of bacterial and fungal communities in the roots and rhizosphere soil of GE, GD, and GA. The results showed that Delftia, Bordetella and norank_f_Xanthobacteraceae were the dominant bacteria in the roots of Geodorum, while norank_f_Xanthobacteraceae, Gaiella and norank_f_norank_o_Gaiellales were the dominant bacteria in the rhizosphere soil of Geodorum. In the roots, the proportion of Mycobacterium in GD_roadside was higher than that in GD_understory, on the contrary, the proportion of Fusarium, Delftia and Bordetella in GD_roadside was lower than that in GD_understory. Compared with the GD_understory, the roots of GD_roadside had lower microbial diversity. In the endangered species GE, Russula was the primary fungus in the roots and rhizosphere soil, with fungal diversity lower than in the more widespread species. Among the widespread species, the dominant fungal genera in the roots and rhizosphere soil were Neocosmospora, Fusarium and Coprinopsis. This study enhances our understanding of microbial composition and diversity, providing fundamental information for future research on microbial contributions to plant growth and ecosystem function in Geodorum.

Influence of weeding methods on rhizosphere soil and root endophytic microbial communities in tea plants

Introduction

Polyethylene mulch is a kind of inorganic mulch widely used in agriculture. The effects of plastic mulch debris on the structure of plant soil and root growth have been fully studied, but their effects on endophytic microbial communities have not been explored to a large extent.

Methods

In this study, High-throughput sequencing of bacterial 16S rRNA genes and fungal ITS region sequences were used to analyze microbial community structure and composition in rhizosphere soil and root endophytic of tea plant under three different weeding methods: polyethylene mulching, hand weeding and no weeding (CK).

Results

The results showed that the weeding methods had no significant effect on the rhizosphere and root endophytic microbial abundance, but the rhizosphere bacterial structure covered by polyethylene mulch was significantly different than hand weeding and CK. The rhizosphere fungal diversity was also significantly higher than the other two analyzed treatments. The community abundance of rhizosphere microorganisms Acidobacteria, Candidatus Rokubacteria and Aspergillus covered by polyethylene mulch decreased significantly, whereas Bradyrhizobium, Solirubrobacterales and Alphaproteobacteria increased significantly. The abundance of bacteria Ktedonobacter, Reticulibacter, Ktedonosporobacter and Dictyobacter communities covered by polyethylene mulch was significantly changed, and the abundance of Fusarium and Nitrobacteraceae was significantly increased. Rhizosphere dominant bacteria were negatively correlated with soil available nitrogen content, while dominant fungi were significantly correlated with soil pH, total nitrogen and total potassium.

Discussion

Polyethylene mulch forms an independent micro-ecological environment. At the same time, the soil nutrient environment was enriched by affecting the nitrogen cycle, and the composition of microbial community was affected. This study elucidated the effects of polyethylene mulch on soil microbial community in tea garden and provided a new theoretical understanding for weed management.

Characterization of Rhizosphere Microbial Diversity and Selection of Plant-Growth-Promoting Bacteria at the Flowering and Fruiting Stages of Rapeseed

Plant rhizosphere microorganisms play an important role in modulating plant growth and productivity. This study aimed to elucidate the diversity of rhizosphere microorganisms at the flowering and fruiting stages of rapeseed (Brassica napus). Microbial communities in rhizosphere soils were analyzed via high-throughput sequencing of 16S rRNA for bacteria and internal transcribed spacer (ITS) DNA regions for fungi. A total of 401 species of bacteria and 49 species of fungi in the rhizosphere soil samples were found in three different samples. The composition and diversity of rhizosphere microbial communities were significantly different at different stages of rapeseed growth. Plant-growth-promoting rhizobacteria (PGPRs) have been widely applied to improve plant growth, health, and production. Thirty-four and thirty-one PGPR strains were isolated from the rhizosphere soil samples collected at the flowering and fruiting stages of rapeseed, respectively. Different inorganic phosphorus- and silicate-solubilizing and auxin-producing capabilities were found in different strains, in addition to different heavy-metal resistances. This study deepens the understanding of the microbial diversity in the rapeseed rhizosphere and provides a microbial perspective of sustainable rapeseed cultivation.

Deinococcus rhizophilus sp.nov., isolated from rhizosphere soil

A spherical, pink, aerobic, Gram-stain-positive bacterial strain (MIMF12T) was isolated from rhizosphere soil collected in the Inner Mongolia Autonomous Region, PR China. Cellular growth of the strain was observed at pH 6.0-8.0 (optimum, pH 7.0), at 20-37 °C (optimum, 28 °C) and with 0-1 % (w/v) NaCl (optimum, 0 %). Phylogenetic analyses based on 16S rRNA gene sequences indicated that strain MIMF12T was most closely related to Deinococcus terrestris SDU3-2T with a similarity value of 96.0 %. The respiratory quinone was menaquinone 8, the major fatty acids were C15 : 1  ω6c and C17 : 1  ω8c, and the major polar lipids were composed of two aminophospholipids, one phospholipid and four unidentified lipids. The G+C content of the genomic DNA was 70.1 mol%. The average nucleotide identity and digital DNA-DNA hybridization values between strain MIMF12T and the closest related type strain SDU3-2T were 88.1 and 52.1 %, respectively. The discovery that MIMF12T differs not only from validly named species in the genus Deinococcus, but also from currently unnamed species in the GDTB, gives us new insights into the genus. Based on phenotypic, chemotaxonomic and phylogenetic characteristics, strain MIMF12T represents a novel species of the genus Deinococcus, for which the name Deinococcus rhizophilus sp. nov. is proposed. The type strain is MIMF12T (=CGMCC 1.61579T=KCTC 43572T).

[Characteristics of anion and cation in rhizosphere soil of saline grassland in North China under different nitrogen addition levels]

We investigated the effects and mechanisms of nitrogen additions (0, 1, 2, 4, 8, 16, 24, 32 g N·m-2·a-1) on contents of anion and cation in rhizosphere soil, bulk soil, and mixed rhizosphere and bulk soil in the heavily salinized grassland in the agro-pastoral ecotone of North China. The results showed that pH of rhizosphere, mixed and bulk soils decreased significantly with the increases of nitrogen addition levels. Moreover, pH of three soil types under the 32 g N·m-2·a-1 treatment decreased by 1.2, 0.9, and 0.6, respectively, while pH of rhizosphere soil decreased by 0.44 compared with the bulk soil. Na+ content of rhizosphere, mixed and bulk soils significantly decreased, while the NO3- content significantly increased. The proportion of Na+ content in total soluble salt content in rhizosphere soil decreased by 14% and that in bulk soil decreased by 12% after the 32 g N·m-2·a-1 addition. NO3- content increased by 29% in rhizosphere soil and by 26% in bulk soil. There was significant negative correlation between pH and NO3- content, and significant positive correlation between pH and Na+ content. The total soluble salt content of rhizosphere soil under the 32 g N·m-2·a-1 treatment was significantly reduced by 31.5%. Collectedly, nitrogen deposition could reduce soil pH and total soluble salt content of rhizosphere soil and alleviate saline-alkali stress.

[Effects of salt stress on bacterial community composition and diversity in rhizosphere soil of Bletilla striata]

Salinization environment affects the normal growth and development of plants, as well as the microbial community in the rhizosphere. To explore the succession dynamics of bacterial communities in the rhizosphere soil of Bletilla striata under salt stress condition, we performed 16S rRNA high-throughput sequencing to determine the bacterial community composition and diversity of B. striata in the rhizosphere under different salt stress concentrations, measured the effects of salt stress on the growth and development of B. striata and soil physicochemical pro-perties, and analyzed the correlation between community composition of rhizosphere bacteria and the soil environmental factors. The results showed that compared with the control, salt stress reduced growth rate and health degree of B. striata, and significantly decreased the content of soil organic matter, nitrogen and phosphorus. Under the salt stress treatment, species diversity and evenness of the bacterial communities in the rhizosphere of B. striata showed a trend of first decreasing and then increasing. There were significant differences in the relative abundance and variation trends of the dominant bacterial taxa in the rhizosphere soil of B. striata at the phylum and class levels between the control and the salt stress treatments. Salt stress intensity and duration were important factors affecting bacterial community composition in the rhizosphere soil of B. striata. Soil organic matter, available nitrogen, and total phosphorus content were key environmental factors affecting the structure of rhizosphere bacterial community composition. Functional genes related to cytoskeleton, cell motility, substance metabolism and signal transduction mechanisms may be involved in the adaptation and stress response of bacterial communities to salt stress. This study would provide theoretical basis and reference for the cultivation management of B. striatain saline area.

nov

Three Gram-stain-negative, aerobic and rod-shaped bacterial strains, designated RD2P54T, M1R5S18T and M1R5S59T, were isolated from a root and rhizosphere soil of Kalidium cuspidatum, in Baotou, PR China. The three strains showed 94.1–98.7 % 16S rRNA gene sequence similarities to Luteimonas strains, indicating they belonged to the genus Luteimonas . The phylogenomic tree based on core genomes showed that strain RD2P54T tightly clustered with Luteimonas salinisoli SJ-92T, while strains M1R5S18T and M1R5S59T clustered with each other and with Luteimonas viscosa XBU10T and Luteimonas saliphila SJ-9T. Though strains M1R5S18T and M1R5S59T showed high 16S rRNA similarity (99.4 %) to each other, the low average nucleotide identity based on blast (ANIb; 88.6 %) and digital DNA–DNA hybridization (dDDH; 31.6 %) values between them indicated that they belonged to two different species. The ANIb and dDDH values of strains RD2P54T, M1R5S18T and M1R5S59T with their closely neighbours are well below the delineation threshold values for identifying strains as representing different species. All three strains take iso-C15 : 0 and summed feature 9 (C16 : 0 10-methyl and/or iso-C17 : 1  ω9c) as major fatty acids, and ubiquinone-8 as the sole respiratory quinone. The major polar lipids of all three strains are diphosphatidylglycerol, phosphatidylglycerol and phosphatidylethanolamine. Based on phenotypic and phylogenetic data, these three strains should be considered to represent three novel species of the genus Luteimonas , for which the names Luteimonas endophytica sp. nov. (type strain RD2P54T=CGMCC 1.61535T =KCTC 92470T), Luteimonas rhizosphaericola sp. nov. (type strain M1R5S18T=CGMCC 1.61537T =KCTC 92469T) and Luteimonas kalidii sp. nov. (type strain M1R5S59T=CGMCC 1.61536T =KCTC 92471T) are proposed.

Effect of continuous planting on Casuarina equisetifolia rhizosphere soil physicochemical indexes, microbial functional diversity and metabolites

Continuous planting has a severe impact on the growth of Casuarina equisetifolia. In this study, the effects of three different long-term monocultures (one, two and three replanting) on the physicochemical indexes, microbial functional diversity, and soil metabolomics were analyzed in C. equisetifolia rhizosphere soil. The results showed that rhizosphere soil organic matter content, cation exchange capacity, total and available nitrogen, total and available phosphorus, and total and available potassium contents significantly decreased with the increasing number of continuous plantings. The evaluation of microbial functional diversity revealed a reduction in the number of soil microorganisms that rely on carbohydrates for carbon sources and an increase in soil microorganisms that used phenolic acid, carboxylic acid, fatty acid, and amines as carbon sources. Soil metabolomics analysis showed a significant decrease in soil carbohydrate content and a significant accumulation of autotoxic acid, amine, and lipid in the C. equisetifolia rhizosphere soil. Consequently, the growth of C. equisetifolia could hinder total nutrient content and their availability. Thus, valuable insights for managing the cultivation of C. equisetifolia and soil remediation were provided.

nov., isolated from the rhizosphere soil of Koelreuteria paniculata and healthy leaves of Xanthium sibiricum

Two actinomycete strains, designated MG62T and CRLD-Y-1, were isolated from rhizosphere soil of Koelreuteria paniculata and healthy leaves of Xanthium sibiricum, respectively, in Hunan province, PR China. They could produce abundant aerial mycelia that generated rod-shaped spores with spiny surfaces. Morphological features of the two strains are typical of the genus Streptomyces. Strains MG62T and CRLD-Y-1 exhibited 99.93 % 16S rRNA gene sequence similarity. The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between them were 99.99 and 100 %, respectively, suggesting that they belonged to the same species. 16S rRNA gene sequences analysis revealed that the two strains belonged to the genus Streptomyces and showed highest similarities to Streptomyces violarus NBRC 13104T (99.07-99.29 %) and Streptomyces arenae ISP 5293T (99.21-99.35 %). Phylogenetic analysis based on 16S rRNA gene sequences indicated that strains MG62T and CRLD-Y-1 were closely related to S. violarus NBRC 13104T and S. arenae ISP 5293T. However, the ANI, dDDH and multilocus sequence analysis evolutionary distance values between the two strains and their relatives provide a robust basis upon which to verify strains MG62T and CRLD-Y-1 as representing a novel species. Moreover, a comprehensive comparison of phenotypic and chemotaxonomic characteristics further confirmed that the two strains were distinct from their relatives. Based on all these data above, strains MG62T and CRLD-Y-1 should represent a novel Streptomyces species, for which the name Streptomyces koelreuteriae sp. nov. is proposed. The type strain is MG62T (=JCM 34747T=MCCC 1K06175T).

[Effects of Aeration Methods on Microbial Diversity and Community Structure in Rice Rhizosphere]

To explore the effects of different aeration methods on the abundance of microorganisms and microorganism community structure in rice rhizosphere soil, two rice varieties, Miyang 46(MY) and Zhenshan 97B(ZS), were used with three aeration treatments:alternate wetting and drying(AWD), continuous flooding and aeration(CFA), and continuous flooding(CF). The diversity of bacterial and fungal communities in rice rhizosphere soil was analyzed using Illumina MiSeq high-throughput sequencing. Soil physical and chemical factors were also analyzed. The results showed that the dominant bacterial communities in rice rhizosphere soil were Chloroflexi, Actinobaciota, Acidobacteria, Proteobacteria, and Firmicutes, and the dominant fungal communities were Ascomycota and Basidiomycota in rice rhizosphere soil. At each growth stage, the relative abundance of Chloroflexi and Acidobacteria was higher in the AWD treatment than in the other treatments, and the relative abundance of Actinobaciota was higher in the CFA treatment than in the other treatments. The relative abundance of Firmicutes was lower in the AWD treatment than in the other treatments. Aeration methods affected the diversity and richness of rhizosphere microbial species. For example, the diversity of bacterial species was higher, and the richness of bacterial species was lower in the AWD treatment than that in the other treatments. The diversity and richness of fungal species were higher in the AWD and CFA treatments than those in the CF treatment. The physical and chemical properties of rhizosphere soil were also affected by aeration method. The soil redox potential(Eh) was the highest in AWD, followed by that in CFA and CF, and significant differences were observed among treatments. The NO3--N content was significantly higher, and the NH4+-N content was significantly lower in the AWD and CFA treatments than in the CF treatment in rhizosphere soil at all growth stages. Correlation analysis showed that the pH and Eh of rhizosphere soil were positively correlated with the diversity of bacterial species, negatively correlated with the richness of bacterial species, and positively correlated with the diversity and richness of fungal species. Redundancy analysis indicated that the relative abundance of Chloroflexi was positively correlated with the pH and NH4+-N content at each period, positively correlated with the Eh and NO3--N content at the tillering and heading stages, and negatively correlated with Eh and NO3--N content at the maturity stage. At each growth stage, the pH and Eh were positively correlated with the relative abundance of Acidobacteria, Proteobacteria, and Basidiomycota and negatively correlated with the relative abundance of Firmicutes and Ascomycota. During the entire growth period, the relative abundance of Ascomycota was negatively correlated with the NO3--N content and positively correlated with the NH4+-N content, and the opposite patterns were observed for the relative abundance of Basidiomycota. In summary, rhizosphere oxygenation enhanced the soil oxygen environment, altered soil physical and chemical properties, and affected microbial community diversity and richness to optimize microbial community structure.

[Correlation between rhizosphere environment and content of medicinal components of Arnebia euchroma]

This study aimed to explore the correlation between rhizosphere soil microorganisms of wild Arnebia euchroma and the content of medicinal components to provide guidance for the selection of the ecological planting base. The total DNA of rhizosphere soil microorganisms of wild A. euchroma was extracted, and the microbial community structure of rhizosphere soil microorganisms was analyzed by IlluminaMiseq high-throughput sequencing technology. The content of total hydroxynaphthoquinone pigment and β,β'-dimethylacrylalkannin in medicinal materials was determined by high-performance liquid chromatography(HPLC). The physicochemical pro-perties of rhizosphere soil of wild A. euchroma in main producing areas were determined, and the correlation of soil microbial abundance with index component content and soil physicochemical properties was analyzed by SPSS software. The results showed that the species composition of rhizosphere fungi and bacteria in A. euchroma from different habitats was similar at the phylum and genus levels, but their relative abundance, richness index(Chao1), and community diversity(Simpson) index were different. Correlation analysis showed that the content of available phosphorus in soil was positively correlated with the content of total hydroxynaphthoquinone pigment and β,β'-dimethylacrylalkannin, and the abundance of five fungal genera such as Solicoccozyma and six bacterial genera such as Pseudo-nocardia and Bradyrhizobium was positively correlated with the content of medicinal components in medicinal materials. The abundance of Bradyrhizobium was significantly positively correlated with the content of β,β'-dimethylacrylalkanin. The abundance of fungi such as Archaeorhizomyces was significantly positively correlated with the content of available phosphorus in rhizosphere soil, and Bradyrhizobium was significantly negatively correlated with soil pH. Therefore, the abundance of fungi and bacteria in the rhizosphere of A. euchroma has a certain correlation with the medicinal components and the physicochemical properties of the rhizosphere soil, which can provide a scientific basis for the selection of ecological planting bases in the later stage.

Effects of maize and soybean intercropping on soil phosphorus bioavailability and microbial community structure in rhizosphere

To investigate the effect of maize/soybean intercropping on rhizosphere soil microbial communities and phosphorus (P) bioavailability, we examined the changes of soil bioavailable P fractions and microbial community characteristics in the monoculture and intercropping systems based on high-throughput sequencing. The results showed that maize/soybean intercropping increased the contents of rhizosphere soil organic matter (SOM), available phosphorus (AP), microbial biomass phosphorus (MBP), and aboveground biomass. The increase of AP was mainly related to the increasing enzyme extracted phosphorus (Enzyme-P) and hydrochloric acid extracted phosphorus (HCl-P) contents. The dominant bacterial phyla under each treatment were Proteobacteria, Actinobacteria, Acidobacteria and Chloroflexi, while the dominant bacterial genera were Nocardioides, Solirubacter, Sphingomonas and Arthrobacter, with Proteobacteria and Sphingomonas having the highest relative abundance. The relative abundance of Proteobacteria and Sphingomonas in intercropping maize rhizosphere soil was significantly higher than that in monoculture, and that of Proteobacteria in intercropping soybean rhizosphere soil was significantly higher than monoculture. Soil properties and P fractions were closely related to the rhizosphere soil microbial composition. In all, maize/soybean intercropping could affect the rhizosphere soil P bioavailability by altering the structure of rhizosphere microbial communities.

Bacterial Microbiome Differences between the Roots of Diseased and Healthy Chinese Hickory (Carya cathayensis) Trees

Carya cathayensis is an important economic nut tree that is endemic to eastern China. As such, outbreaks of root rot disease in C. cathayensis result in reduced yields and serious economic losses. Moreover, while soil bacterial communities play a crucial role in plant health and are associated with plant disease outbreaks, their diversity and composition in C. cathayensis are not clearly understood. In this study, Proteobacteria, Acidobacteria, and Actinobacteria were found to be the most dominant bacterial communities (accounting for approximately 80.32% of the total) in the root tissue, rhizosphere soil, and bulk soil of healthy C. cathayensis specimens. Further analysis revealed the abundance of genera belonging to Proteobacteria, namely, Acidibacter, Bradyrhizobium, Paraburkholderia, Sphaerotilus, and Steroidobacter, was higher in the root tissues of healthy C. cathayensis specimens than in those of diseased and dead trees. In addition, the abundance of four genera belonging to Actinobacteria, namely, Actinoallomurus, Actinomadura, Actinocrinis, and Gaiella, was significantly higher in the root tissues of healthy C. cathayensis specimens than in those of diseased and dead trees. Altogether, these results suggest that disruption in the balance of these bacterial communities may be associated with the development of root rot in C. cathayensis, and further, our study provides theoretical guidance for the isolation and control of pathogens and diseases related to this important tree species.

The Composition and Function of the Rhizosphere Bacterial Community of Paeonia lactiflora Varies with the Cultivar

The composition and diversity of the rhizosphere microbial community maintain the stability of the root microclimate, and several studies have focused on this aspect of rhizosphere microorganisms. However, how these communities vary with cultivars of a species is not completely understood. Paeonia lactiflora-a perennial herb species of the family Paeoniaceae-includes a wide variety of cultivars, with rich rhizosphere microbial resources. Hence, we studied the differences in rhizosphere bacterial communities associated with eight P. lactiflora cultivars. We noted that Actinobacteria, Proteobacteria, Acidobacteria, Bacteroidetes, Firmicutes, Verrucomicrobia, Planctomycetes and Chloroflexi were the dominant phyla associated with the cultivars. The composition of rhizosphere bacterial community of different cultivars was highly similar at taxonomic levels, but there were slightly differences in the relative abundance. LEfSe analysis showed that the cultivars "Sheng Tao Hua" and "Zi Lou Xian Jin" exhibited the most biomarkers. Differential ASV analysis revealed the maximum difference in ASV abundance between "Lian Tai" and "Zi Hong Zheng Hui", as well as between "Sheng Tao Hua" and "Tao Hua Fei Xue", and the maximum similarity between "Duo Ye Zi" and "Xue Feng". Co-occurrence network analysis revealed that rhizosphere bacteria in most cultivars maintain homeostasis by cooperation, wherein Actinobacteria and Proteobacteria played a vital role. In addition, microbial resources related to cultivars like bioremediation, organic degradation and resistance to diseases are found. This study revealed the structures of the rhizosphere bacterial communities associated with different cultivars of P. lactiflora and explored their stress resistance potential, which can be used to guide future agricultural practices.

Luteimonas suaedae sp. nov., a novel bacterium isolated from rhizosphere of Suaeda aralocaspica (Bunge) Freitag & Schütze

Light yellowish-white colonies of a bacterial strain, designated LNNU 24178T, were isolated from the rhizosphere soil of halophyte Suaeda aralocaspica (Bunge) Freitag and Schütze grown at Shihezi district, Xinjiang, PR China. Cells were Gram-stain-negative, non-flagellum-forming, rod-shaped and non-motile. The results of phylogenetic analysis based on the 16S rRNA gene sequence indicated that LNNU 24178T represented a member of the genus Luteimonas and shared the highest sequence similarity with Luteimonas yindakuii CGMCC 1.13927T (97.1 %) and lower sequence similarity (< 97.0 %) to other known species. The genomic DNA G+C content of LNNU 24178T was 68.8 %. The average nucleotide identity (ANI) values between LNNU 24178T and Luteimonas yindakuii CGMCC 1.13927T, Luteimonas mephitis DSM 12574T, Luteimonas arsenica 26-35T and Luteimonas huabeiensis HB2T were 78.7, 78.6, 78.4 and 80.0 %, respectively. The digital DNA-DNA hybridisation (dDDH) values between LNNU 24178T and L. yindakuii CGMCC 1.13927T, L. mephitis DSM 12574T, L. arsenica 26-35T and L. huabeiensis HB2T were 22.0, 22.3, 22.2 and 23.5 %, respectively. The respiratory quinone detected in LNNU 24178T was ubiquinone-8 (Q-8). The major fatty acids (> 5.0 %) of LNNU 24178T were identified as iso-C15 : 0 (33.9 %), iso-C17 : 0 (8.7 %), iso-C11 : 0 (6.2 %), iso-C16 : 0 (5.7 %), C16 : 0 (5.3 %) and summed feature 9 (iso-C17 : 1ω9c/10-methyl C16 : 0) (21.1 %). The major polar lipids of LNNU 24178T were diphosphatidylglycerol (DPG), phosphatidylglycerol (PG), phosphatidylethanolamine (PE), one unidentified phospholipid (PL), one unidentified glycolipid (GL) and three unidentified lipids. According to the data obtained from phenotypic, chemotaxonomic and phylogenetic analyses, strain LNNU 24178T represents a novel species of the genus Luteimonas, for which the name Luteimonas suaedae sp. nov. is proposed, with LNNU 24178T (= CGMCC 1.17331T= KCTC 62251T) as the type strain.

Insights into the mechanisms of microbiome and metabolome changes mediated by understory interplanting mode in Polygonatum sibiricum

Background

Polygonatum sibiricum is an understory economic plant, and its dried rhizome is a traditional Chinese medicine. The purpose of this study was to connect the quality improvement of the understory plant P. sibiricum with specific microorganisms.

Methods

Amplicon and metabolome sequencing were conducted for P. sibiricum interplanted under three types of trees and in the field, and the relationship between the microbiome and secondary metabolism was explored.

Results

Principal component analysis (PCA) divided field cultivated and understory interplanted groups into two classes. A total of 95 different metabolites were found, with four expression patterns. The alpha diversity of rhizosphere bacteria and endosphere fungi in the understory interplanted group was significantly higher than that in the farmland cultivated group. There were 276 different rhizosphere microorganism genera among the four groups; however, only 33 different endosphere genera were observed, indicating that endophytic microbial diversity was relatively stable within the P. sibiricum rhizome, especially for endosphere bacteria. Cointertia analysis (CoIA) suggested that the metabolite changes in P. sibiricum induced by interplanting under different trees were more strongly affected by rhizosphere microorganisms than by endosphere microorganisms. In addition, the interactions between rhizosphere microorganisms and metabolites in the farmland group were weakened compared with those in the underplanted groups. Canonical correspondence analysis (CCA) showed that Aspergillus and Ellin6067 had the greatest influence on the metabolites. Myrmecridium, as a shared microbe in the rhizosphere and endosphere, had interaction effects with the largest number of microbes.

Conclusion

This study revealed the interactions between the microbes and metabolites in P. sibiricum and systematically explored the mechanism underlying their correlation, which was mediated by the understory interplanting mode. This study provides feasible strategies for improving the medicinal value of P. sibiricum by regulating microorganisms.

Effects of tea oil camellia (Camellia oleifera Abel.) shell-based organic fertilizers on the physicochemical property and microbial community structure of the rhizosphere soil

Soil microorganisms play important roles in promoting soil ecosystem restoration, but much of the current research has been limited to changes in microbial community structure in general, and little is known regarding the soil physicochemical property and microbial community structure. In this study, four organic fertilizers were first prepared based on tea oil camellia shell (TOCS). Our findings indicate that the application of BOFvo increased both total pore volume and BET surface area of the rhizosphere soils, as well there was a remarkable enhancement in total organic matter (TOM), total nitrogen (TN), available nitrogen (AN), total phosphorus (TP), total potassium (TK), and available potassium (AK) contents of the rhizosphere soils. Meanwhile, in comparison to the CK and CF groups, the utilization of BOFvo led to a substantial increase in both average yield and fruiting rate per plant at maturity, as well resulted in a significant increase in TN and TP contents of tea oil camellia leaves. Furthermore, our findings suggest that the application of TOCS-based organic fertilizers significantly enhances the microbial diversity in the rhizosphere soils with Proteobacteria and Ascomycota being the dominant bacterial and fungal phyla, respectively, and Rhodanobacter and Fusarium being the dominant bacterial and fungal genus, respectively. Redundancy analysis (RDA) indicates that the physicochemical characteristics of TOCS-based organic fertilizers had a significant impact on the composition and distribution of microbial communities in the rhizosphere soils. This study will facilitate the promotion and application of TOCS-based organic fertilizers, thereby establishing a foundation for the reuse of tea oil camellia waste resources.

Temporal Variability of Gallium in Natural Plants

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.

Chryseobacterium herbae Isolated from the Rhizospheric Soil of Pyrola calliantha H. Andres in Segrila Mountain on the Tibetan Plateau

A non-motile, Gram-staining-negative, orange-pigmented bacterium called herbae pc1-10T was discovered in Tibet in the soil around Pyrola calliantha H. Andres' roots. The isolate thrived in the temperature range of 10-30 °C (optimal, 25 °C), pH range of 5.0-9.0 (optimum, pH = 6.0), and the NaCl concentration range of 0-1.8% (optimal, 0%). The DNA G+C content of the novel strain was 37.94 mol%. It showed the function of dissolving organophosphorus, acquiring iron from the environment by siderophore and producing indole acetic acid. Moreover, the genome of strain herbae pc1-10T harbors two antibiotic resistance genes (IND-4 and AdeF) encoding a β-lactamase, and the membrane fusion protein of the multidrug efflux complex AdeFGH; antibiotic-resistance-related proteins were detected using the Shotgun proteomics technology. The OrthoANIu values between strains Chryseobacterium herbae pc1-10T; Chryseobacterium oleae CT348T; Chryseobacterium kwangjuense KJ1R5T; and Chryseobacterium vrystaatense R-23566T were 90.94%, 82.96%, and 85.19%, respectively. The in silico DDH values between strains herbae pc1-10T; C. oleae CT348T; C. kwangjuense KJ1R5T; and C. vrystaatense R-23566T were 41.7%, 26.6%, and 29.7%, respectively. Chryseobacterium oleae, Chryseobacterium vrystaatense, and Chryseobacterium kwangjuense, which had 16S rRNA gene sequence similarity scores of 97.80%, 97.52%, and 96.75%, respectively, were its closest phylogenetic relatives. Chryseobacterium herbae sp. nov. is proposed as the designation for the strain herbae pc1-10T (=GDMCC 1.3255 = JCM 35711), which represented a type species based on genotypic and morphological characteristics. This study provides deep knowledge of a Chryseobacterium herbae characteristic description and urges the need for further genomic studies on microorganisms living in alpine ecosystems, especially around medicinal plants.

Integrated metagenomics and metabolomics analysis reveals changes in the microbiome and metabolites in the rhizosphere soil of Fritillaria unibracteata

Fritillaria unibracteata (FU) is a renowned herb in China that requires strict growth conditions in its cultivation process. During this process, the soil microorganisms and their metabolites may directly affect the growth and development of FU, for example, the pathogen infection and sipeimine production. However, few systematic studies have reported the changes in the microbiome and metabolites during FU cultivation thus far. In this work, we simultaneously used metagenomics and metabolomics technology to monitor the changes in microbial communities and metabolites in the rhizosphere of FU during its cultivation for one, two, and three years. Moreover, the interaction between microorganisms and metabolites was investigated by co-occurrence network analysis. The results showed that the microbial composition between the three cultivation-year groups was significantly different (2020-2022). The dominant genera changed from Pseudomonas and Botrytis in CC1 to Mycolicibacterium and Pseudogymnoascus in CC3. The relative abundances of beneficial microorganisms decreased, while the relative abundances of harmful microorganisms showed an increasing trend. The metabolomics results showed that significant changes of the of metabolite composition were observed in the rhizosphere soil, and the relative abundances of some beneficial metabolites showed a decreasing trend. In this study, we discussed the changes in the microbiome and metabolites during the three-year cultivation of FU and revealed the relationship between microorganisms and metabolites. This work provides a reference for the efficient and sustainable cultivation of FU.

Improvement of growth, yield and associated bacteriome of rice by the application of probiotic Paraburkholderia and Delftia

Plant probiotic bacteria enhance growth and yield of crop plants when applied at the appropriate time and dose. Two rice probiotic bacteria, Paraburkholderia fungorum strain BRRh-4 and Delftia sp. strain BTL-M2 promote growth and yield of plants. However, no information is available on application of these two bacteria on growth, yield, and diversity and population of bacteriome in roots and rhizosphere soils of the treated rice plants. This study aimed to assess the effect of BRRh-4 and BTL-M2 application on growth, yield and bacteriome in roots and rhizosphere soil of rice under varying doses of N, P and K fertilizers. Application of BRRh-4 and BTL-M2 strains significantly (p < 0.05) increased seed germination, growth and yield of rice compared to an untreated control. Interestingly, the grain yield of rice by these bacteria with 50% less of the recommended doses of N, P, and K fertilizers were statistically similar to or better than the rice plants treated with 100% doses of these fertilizers. Targeted amplicon (16S rRNA) sequence-based analysis revealed significant differences (PERMANOVA, p = 0.00035) in alpha-diversity between the root (R) and rhizosphere soil (S) samples, showing higher diversity in the microbial ecosystem of root samples. Additionally, the bacteriome diversity in the root of rice plants that received both probiotic bacteria and chemical fertilizers were significantly higher (PERMANOVA, p = 0.0312) compared to the rice plants treated with fertilizers only. Out of 185 bacterial genera detected, Prevotella, an anaerobic and Gram-negative bacterium, was found to be the predominant genus in both rhizosphere soil and root metagenomes. However, the relative abundance of Prevotella remained two-fold higher in the rhizosphere soil metagenome (52.02%) than in the root metagenome (25.04%). The other predominant bacterial genera detected in the rice root metagenome were Bacillus (11.07%), Planctomyces (4.06%), Faecalibacterium (3.91%), Deinococcus (2.97%), Bacteroides (2.61%), and Chryseobacterium (2.30%). On the other hand, rhizosphere soil metagenome had Bacteroides (12.38%), Faecalibacterium (9.50%), Vibrio (5.94%), Roseomonas (3.40%), and Delftia (3.02%). Interestingly, we found the presence and/or abundance of specific genera of bacteria in rice associated with the application of a specific probiotic bacterium. Taken together, our results indicate that improvement of growth and yield of rice by P. fungorum strain BRRh-4 and Delftia sp. strain BTL-M2 is likely linked with modulation of diversity, structures, and signature of bacteriome in roots and rhizosphere soils. This study for the first time demonstrated that application of plant growth promoting bacteria significantly improve growth, yield and increase the diversity of bacterial community in rice.

Temporal and spatial changes in rhizosphere bacterial diversity of mountain Rhododendron mucronulatum

To better conserve the ecology of the wild Rhododendron mucronulatum range, we studied the rhizosphere microenvironment of R. mucronulatum in Beijing's Yunmeng Mountain National Forest Park. R. mucronulatum rhizosphere soil physicochemical properties and enzyme activities changed significantly with temporal and elevational gradients. The correlations between soil water content (SWC), electrical conductivity (EC), organic matter content (OM), total nitrogen content (TN), catalase activity (CAT), sucrose-converting enzyme activity (INV), and urease activity (URE) were significant and positive in the flowering and deciduous periods. The alpha diversity of the rhizosphere bacterial community was significantly higher in the flowering period than in the deciduous period, and the effect of elevation was insignificant. The diversity of the R. mucronulatum rhizosphere bacterial community changed significantly with the change in the growing period. A network analysis of the correlations revealed stronger linkages between the rhizosphere bacterial communities in the deciduous period than in the flowering period. Rhizomicrobium was the dominant genus in both periods, but its relative abundance decreased in the deciduous period. Changes in the relative abundance of Rhizomicrobium may be the main factor influencing the changes in the R. mucronulatum rhizosphere bacterial community. Moreover, the R. mucronulatum rhizosphere bacterial community and soil characteristics were significantly correlated. Additionally, the influence of soil physicochemical properties on the rhizosphere bacterial community was larger than that of enzyme activity on the bacterial community. We mainly analyzed the change patterns in the rhizosphere soil properties and rhizosphere bacterial diversity of R. mucronulatum during temporal and spatial variation, laying the foundation for further understanding of the ecology of wild R. mucronulatum.

Impact of Insect-Resistant Transgenic Maize 2A-7 on Diversity and Dynamics of Bacterial Communities in Rhizosphere Soil

Artificial modification of Bacillus thuringiensis (Bt) proteins can effectively improve their resistance to target pests, but the effect of such modification on the diversity of rhizosphere microorganisms remains unclear. Transgenic maize 2A-7 contains two artificially modified Bt proteins, mCry1Ab and mCry2Ab. These proteins can enter soil and pose a potential threat to soil microbial diversity. To assess their impacts on rhizosphere bacteria communities, the contents of the two Bt proteins and changes in bacterial community diversity in the rhizosphere soils of transgenic maize 2A-7 and its control variety were analyzed at different growth stages in 2020. The results showed that the two Bt proteins were detected at low levels in the rhizosphere soils of 2A-7 plants. No significant differences in soil bacterial diversity were detected between 2A-7 and its control variety at any of the growth stages. Bioinformatics analysis indicated that the growth stage, rather than the cultivar, was the main factor causing changes in bacterial communities. This research provides valuable data for understanding the impact of Bt crops on the soil microbiome, and establishes a theoretical basis for evaluation of their safety.

Long-term fertilization coupled with rhizobium inoculation promotes soybean yield and alters soil bacterial community composition

Microbial diversity is an important indicator of soil fertility and plays an indispensable role in farmland ecosystem sustainability. The short-term effects of fertilization and rhizobium inoculation on soil microbial diversity and community structure have been explored extensively; however, few studies have evaluated their long-term effects. Here, we applied quantitative polymerase chain reaction (qPCR) and amplicon sequencing to characterize the effect of 10-year fertilizer and rhizobium inoculation on bacterial communities in soybean bulk and rhizosphere soils at the flowering-podding and maturity stages. Four treatments were examined: non-fertilization control (CK), phosphorus and potassium fertilization (PK), nitrogen and PK fertilization (PK + N), and PK fertilization and Bradyrhizobium japonicum 5821 (PK + R). Long-term co-application of rhizobium and PK promoted soybean nodule dry weight by 33.94% compared with PK + N, and increased soybean yield by average of 32.25%, 5.90%, and 5.00% compared with CK, PK, and PK + N, respectively. The pH of PK + R was significantly higher than that of PK and PK + N at the flowering-podding stage. The bacterial abundance at the flowering-podding stage was positively correlated with soybean yield, but not at the maturity stage. The significant different class Gemmatimonadetes, and the genera Gemmatimonas, and Ellin6067 in soil at the flowering-podding stage were negatively correlated with soybean yield. However, the bacterial community at class and genus levels at maturity had no significant effect on soybean yield. The key bacterial communities that determine soybean yield were concentrated in the flowering-podding stage, not at maturity stage. Rhizosphere effect, growth period, and treatment synergies resulted in significant differences in soil bacterial community composition. Soil organic matter (OM), total nitrogen (TN), pH, and available phosphorus (AP) were the main variables affecting bacterial community structure. Overall, long-term co-application of rhizobium and fertilizer not only increased soybean yield, but also altered soil bacterial community structure through niche reconstruction and microbial interaction. Rhizobium inoculation plays key role in reducing nitrogen fertilizer application and promoting sustainable agriculture practices.

viridulum

Lily Fusarium wilt disease caused by Fusarium spp. spreads rapidly and is highly destructive, leading to a severe reduction in yield. In this study, lily (Lilium brownii var. viridulum) bulbs were irrigated after planting with suspensions of two Bacillus strains that effectively control lily Fusarium wilt disease to assess their effects on the rhizosphere soil properties and microbial community. A high-throughput sequencing of microorganisms in the rhizosphere soil was performed and the soil physicochemical properties were measured. The FunGuild and Tax4Fun tools were used for a functional profile prediction. The results showed that Bacillus amyloliquefaciens BF1 and B. subtilis Y37 controlled lily Fusarium wilt disease with control efficacies of 58.74% and 68.93%, respectively, and effectively colonized the rhizosphere soil. BF1 and Y37 increased the bacterial diversity and richness of the rhizosphere soil and improved the physicochemical properties of the soil, thereby favoring the proliferation of beneficial microbes. The relative abundance of beneficial bacteria was increased and that of pathogenic bacteria was decreased. Bacillus abundance in the rhizosphere was positively correlated with most soil physicochemical properties, whereas Fusarium abundance was negatively correlated with most physicochemical properties. Functional prediction revealed that irrigation with BF1 and Y37 significantly upregulated glycolysis/gluconeogenesis among metabolism and absorption pathways. This study provides insights into the mechanism by which two Bacillus strains with antifungal activity, BF1 and Y37, antagonize plant pathogenic fungi and lays the foundation for their effective application as biocontrol agents.

Responses of Fungal Assembly and Co-Occurrence Network of Rhizosphere Soil to Amaranthus palmeri Invasion in Northern China

The interaction between invasive plants and soil microbial communities is critical for plant establishment. However, little is known about the assembly and co-occurrence patterns of fungal communities in the rhizosphere soil of Amaranthus palmeri. The soil fungal communities and co-occurrence networks were investigated in 22 invaded patches and 22 native patches using high-throughput Illumina sequencing. Despite having little effect on alpha diversity, plant invasion significantly altered the composition of the soil fungal community (ANOSIM, p < 0.05). Fungal taxa associated with plant invasion were identified using linear discriminant analysis effect size (LEfSe). In the rhizosphere soil of A. palmeri, Basidiomycota was significantly enriched, while Ascomycota and Glomeromycota were significantly reduced when compared to native plants. At the genus level, the invasion of A. palmeri dramatically increased the abundance of beneficial fungi and potential antagonists such as Dioszegia, Tilletiopsis, Colacogloea, and Chaetomium, while it significantly decreased the abundance of pathogenic fungi such as Alternaria and Phaeosphaeria. Plant invasion reduced the average degree and average path length, and increased the modularity value, resulting in a less complex but more effective and stable network. Our findings improved the knowledge of the soil fungal communities, network co-occurrence patterns, and keystone taxa in A. palmeri-invaded ecosystems.

Enhancement of phytoextraction efficiency coupling Pteris vittata with low-dose biochar in arsenic-contaminated soil

Phytoremediation of arsenic (As) by Pteris vittata (P. vittata) is a cost-effective and environmentally friendly method for restoring As-contaminated sites. However, the phytoextraction efficiency is low in some cases, such as clay soil, thus biochar was applied to enhance the efficiency of As extraction. The paper investigated the effect of biochar on soil characteristic, As mobility, and As uptake in P. vittata with a 90-day greenhouse experiment. Biochar derived from rice straw was added at rates of 0.5, 1.5, and 4% (w/w). The results showed that, under biochar amendment, soil pH raised from 5.24 to 6.03 and 4.91 to 5.85, soil dissolved organic carbon (DOC) increased 11.1-46.1% and 2.8-11.2%, respectively, in rhizosphere and bulk soils. Biochar also increased soil catalase (CAT) activity significantly, especially for the rhizosphere soil. Besides, biochar increased the labile As in the soils and transfer coefficient from roots to aboveground, thereby enhancing As accumulation by P. vittata tissues. The accumulation of As in fronds of P. vittata was up to 350 mg kg-1 in 1.5% biochar, which was more than twice the control and far beyond other biochar treatments. The results indicate that biochar addition is favorable to improve phytoremediation of P. vittata in As-contaminated soil and 1.5% (w/w) biochar may be a reasonable application ratio, thus providing an effective solution to enhance the efficiency of As phytoextraction.

nov., two novel actinomycetes isolated from rhizosphere soil of cotton

Two Gram-positive, aerobic and non-motile actinomycetes, designated S1-96^T and N2-109^T, were isolated from soils collected from a cotton field. They are described as representing two novel species of genera Actinophytocola and Streptomyces through a polyphasic approach. Analysis of 16S rRNA gene sequences revealed that strains S1-96^T and N2-109^T showed highest similarity to Actinophytocola xinjiangensis CGMCC 4.4663^T (99.10 %) and Streptomyces iconiensis BNT558^T (98.21 %), respectively. Phylogenetic analyses based on 16S rRNA and core genes confirmed the close relationships of these strains. Genomic analyses further supported the novel taxonomic delimitation of these two species based on digital DNA-DNA hybridization and average nucleotide identity. Strains S1-96^T and N2-109^T contained MK-9(H₄) and MK-9(H₆) as the most abundant menaquinone, respectively. High abundances of iso-fatty acids were detected in both strains, which was similar to their close relatives. Physiological and polar lipid analyses also revealed differences between these strains and their phylogenetic neighbours, supporting their taxonomic delimitation as novel species. The names Actinophytocola gossypii sp. nov. (type strain S1-96^T=JCM 34412^T=CGMCC 4.7707^T) and Streptomyces gossypii sp. nov. (type strain N2-109^T=JCM 34628^T=CGMCC 4.7717^T) are proposed.

Plants changed the response of bacterial community to the nitrogen and phosphorus addition ratio

INTRODUCTION

Human activities have increased the nitrogen (N) and phosphorus (P) supply ratio of the natural ecosystem, which affects the growth of plants and the circulation of soil nutrients. However, the effect of the N and P supply ratio and the effect of plant on the soil microbial community are still unclear.

METHODS

In this study, 16s rRNA sequencing was used to characterize the response of bacterial communities in Phragmites communis (P.communis) rhizosphere and non-rhizosphere soil to N and P addition ratio.

RESULTS

The results showed that the a-diversity of the P.communis rhizosphere soil bacterial community increased with increasing N and P addition ratio, which was caused by the increased salt and microbially available C content by the N and P ratio. N and P addition ratio decreased the pH of non-rhizosphere soil, which consequently decreased the a-diversity of the bacterial community. With increasing N and P addition ratio, the relative abundance of Proteobacteria and Bacteroidetes increased, while that of Actinobacteria and Acidobacteria decreased, which reflected the trophic strategy of the bacterial community. The bacterial community composition of the non-rhizosphere soil was significantly affected by salt, pH and total carbon (TC) content. Salt limited the relative abundance of Actinobacteria, and increased the relative abundance of Bacteroidetes. The symbiotic network of the rhizosphere soil bacterial community had lower robustness. This is attributed to the greater selective effect of plants on the bacterial community influenced by nutrient addition.

DISCUSSION

Plants played a regulatory role in the process of N and P addition affecting the bacterial community, and nutrient uptake by the root system reduced the negative impact of N and P addition on the bacterial community. The variations in the rhizosphere soil bacterial community were mainly caused by the response of the plant to the N and P addition ratio.

The layout measures of micro-sprinkler irrigation under plastic film regulate tomato soil bacterial community and root system

INTRODUCTION

The change in rhizosphere soil bacterial community and root system under new water-saving device is not clear.

METHODS

A completely randomized experimental design was used to explore the effects of different micropore group spacing (L1: 30 cm micropore group spacing, L2: 50 cm micropore group spacing) and capillary arrangement density (C1: one pipe for one row, C2: one pipe for two rows, C3: one pipe for three rows) on tomato rhizosphere soil bacteria community, roots and tomato yield under MSPF. The bacteria in tomato rhizosphere soil were sequenced by 16S rRNA gene amplicon metagenomic sequencing technology, the interaction of bacterial community, root system and yield in tomato rhizosphere soil was quantitatively described based on regression analysis.

RESULTS

Results showed that L1 was not only beneficial to the development of tomato root morphology, but also promoted the ACE index of tomato soil bacterial community structure and the abundance of nitrogen and phosphorus metabolism functional genes. The yield and crop water use efficiency (WUE) of spring tomato and autumn tomato in L1 were about 14.15% and 11.27%, 12.64% and 10.35% higher than those in L2. With the decrease of capillary arrangement density, the diversity of bacterial community structure in tomato rhizosphere soil decreased, and the abundance of nitrogen and phosphorus metabolism functional genes of soil bacteria also decreased. The small abundance of soil bacterial functional genes limited the absorption of soil nutrients by tomato roots and roots morphological development. The yield and crop water use efficiency of spring and autumn tomato in C2 were significantly higher than those in C3 about 34.76% and 15.23%, 31.94% and 13.91%, respectively. The positive interaction between soil bacterial community and root morphological development of tomato was promoted by the capillary layout measures of MSPF.

DISCUSSION

The L1C2 treatment had a stable bacterial community structure and good root morphological development, which positively promoted the increase of tomato yield. The interaction between soil microorganisms and roots of tomato was regulated by optimizing the layout measures of MSPF to provide data support for water-saving and yield-increasing of tomato in Northwest China.

[Effects of Chemical Fertilizer Reduction Substitute with Organic Fertilizer on Soil Functional Microbes and Lemon Yield and Quality]

To clarify the effects of non-rhizosphere/rhizosphere soil functional microbes (nitrifiers, denitrifiers, and phosphorus-solubilizing microorganisms) on lemon yield and quality, the lemon fruit and non-rhizosphere/rhizosphere soil were selected as subjects. To explore the correlation between non-rhizosphere/rhizosphere soil functional microbes and lemon yield and quality under a chemical fertilizer reduction substitute with organic fertilizer, traditional fruit quality determination and multiple molecular techniques were used. The results showed that:① 30% chemical fertilizer reduction substitute with organic fertilizer increased the nitrification intensity and phosphatase activity but effectively controlled the denitrifying enzyme activity. ② The chemical fertilizer reduction substitute with organic fertilizer significantly decreased the abundances of nitrifiers and nirS/nirK-harboring denitrifiers and significantly increased the abundances of nosZ-harboring denitrifier and phoD-harboring microorganisms. However, the diversities of functional microbial community structure did not have clear regularity under chemical fertilizer reduction substitute with organic fertilizer. ③ Compared with that under the application of chemical fertilizer and organic fertilizer alone, lemon yield and quality were the highest under the 30% reduction of chemical fertilizer substitute with organic fertilizer. ④ Nitrogen and its related microbes significantly affected lemon yield through internal and external quality. Phosphorus and its related microbes affected lemon yield mainly through internal quality. In addition, the influence factors of non-rhizosphere soil and rhizosphere soil on lemon intrinsic quality were obviously different. Altogether, these results showed that the 30% reduction of chemical fertilizer substitute with organic fertilizer significantly affected soil nitrogen and phosphorus functional microorganisms and further improved lemon yield and quality.

and Actinomadura litoris OS3-89, isolated from rhizosphere soil of cactus

Two mycelium-forming actinobacterial strains, designated OS3-83 ^T and OS3-89, were isolated from rhizosphere soil of a cactus (Opuntia ficus-indica) sampled on Mara Island, Jeju, Republic of Korea. Both of the isolates were found to grow at 20-37 °C, pH 6.0-10.0 and with 0-2 % (w/v) NaCl. Their taxonomic positions were investigated by a polyphasic approach. Strains OS3-83^T and OS3-89 were most closely related to the type strain of Actinomadura litoris (99.5 % and 98.9 % 16S rRNA gene sequence similarity, respectively). Both of the isolates shared 99.2 % sequence similarity to each other. Morphological and chemotaxonomic characteristics supported the affiliation of the two isolates to the genus Actinomadura. 16S rRNA gene phylogeny exhibited that strain OS3-83^T formed a tight cluster with A. litoris, while strain OS3-89 occupied a position located remotely from A. litoris. Nevertheless, phylogenomic analysis based on 92 core gene sequences showed that both of the isolates formed a tight clade with A. litoris. The values of average nucleotide identity and digital DNA-DNA hybridization between strain OS3-83^T and the closest relative, A. litoris, were 92.2 and 46.2 %, respectively, whereas strain OS3-89 shared an average nucleotide identity value of 97.5 % and a digital DNA-DNA hybridization value of 76.9 % with A. litoris. These results strongly suggested that strain OS3-83^T (=KACC 19752^T=NBRC 114688^T) represents a novel species and strain OS3-89 (=KACC 19753=NBRC 114400) is a strain of A. litoris. On the basis of the data obtained here, strain OS3-83^T is considered to represent a new species of the genus Actinomadura, for which the name Actinomadura terrae sp. nov. is proposed.

nov., isolated from paddy rhizosphere soil and formal proposal to reclassify Streptomyces albulus as a later heterotypic synonym of Streptomyces noursei

The taxonomic position of a novel actinomycete, designated strain RS10V-4^T, was determined using a polyphasic approach. Strain RS10V-4^T was isolated from paddy rhizosphere soil of rice plant (Oryzae sativa L.). The morphological, physiological and chemotaxonomic properties were consistent with its classification in the genus Streptomyces. On the basis of 16S rRNA gene sequence analysis, strain RS10V-4^T belongs to the genus Streptomyces and had the highest sequence similarity to Streptomyces noursei NBRC 15452^T (98.3 %). The G+C content of the genomic DNA was 73.8 %. Digital DNA-DNA hybridization and average nucleotide identity values between the genome sequences of strain RS10V-4^T and S.noursei ATCC 11455^T were lower than the recommendation threshold values for the recognition of species within the same genus. The whole-cell hydrolysates of strain RS10V-4 ^T contained ll -diaminopimelic acid as the diagnostic diamino acid and the whole-cell sugars were glucose and ribose. The predominant menaquinones were MK-9(H₆) and MK-9(H₈). The predominant cellular fatty acids (>10 %) were iso-C_16 : 0, anteiso-C_15 : 0, iso-C_14 : 0 and iso-C_15 : 0. The polar lipids of strain RS10V-4^T contained diphosphatidylglycerol, hydroxyphosphatidylethanolamine, phosphatidylethanolamine, phosphatidylinositol, an unidentified aminolipid, two unidentified lipids and an unidentified phospholipid. On the basis of these phenotypic and genotypic characteristics, it is supported that strain RS10V-4^T represents a novel species of the genus Streptomyces, for which the name Streptomyces rhizoryzae sp. nov. is proposed. The type strain is RS10V-4^T (=TBRC 15167^T=NBRC 115345^T). In addition, the comparison of the whole genome sequences and phenotypic features suggested that S. noursei and S. albulus belong to the same species. Therefore, it is proposed that S. albulus is reclassified as a later heterotypic synonym of S. noursei.

Bacillus benefits the competitive growth of Ambrosia artemisiifolia by increasing available nutrient levels

Bacillus can help plants to acquire nutrients either directly or indirectly. However, the role of Bacillus community on the competitive growth of invasive Ambrosia artemisiifolia is poorly understood. Native Setaria viridis is often found in areas that have been invaded by A. artemisiifolia. We sought to determine whether the quantitative and/or qualitative differences in the Bacillus community present on the invasive A. artemisiifolia and native S.viridis provide a competitive advantage to the invasive over native species. A field experiment was established to imitate the invasion of A. artemisiifolia. The 16S rRNA gene was commercially sequenced to identify the bacilli isolated from the rhizosphere soil of field-grown A. artemisiifolia and S. viridis. The Bacillus communities in their rhizosphere were compared, and their effects on the competitive growth of A. artemisiifolia and S. viridis were tested in the pot experiments. Bacillus in the rhizosphere soil of A. artemisiifolia significantly enhanced its intra-specific competitive ability. The relative abundance of B. megaterium in the rhizosphere soil of A. artemisiifolia was significantly higher than that of S. viridis. Inoculation with B. megaterium that was isolated from the rhizosphere soil of both A. artemisiifolia and S. viridis significantly enhanced the relative competitiveness of A. artemisiifolia and inhibited that of S. viridis. The higher abundance of B. megaterium in the rhizosphere of A. artemisiifolia creates higher levels of available nutrients than that in the native S. viridis, which enhance the competitive growth of A. artemisiifolia. The result helps to discover the mechanism of Bacillus community in the invasion of A. artemisiifolia.

Effects of nitrogen input on soil bacterial community structure and soil nitrogen cycling in the rhizosphere soil of Lycium barbarum L

Lycium barbarum L., goji berry, is a precious traditional Chinese medicine and it is homology of medicine and food. Its growth is heavily dependent on nitrogen. The use of chemical fertilizers has significantly promoted the yield of goji berry and the development of the L. barbarum L. industry. However, crop plants are inefficient in the acquisition and utilization of applied nitrogen, it often leads to excessive application of nitrogen fertilizers by producers, which cause negatively impact to the environment ultimately. The exploration of an interaction model which deals with crops, chemical fertilizers, and rhizosphere microbes to improve nitrogen use efficiency, is, therefore, an important research objective to achieve sustainable development of agriculture greatly. In our study, we explored the effects of nitrogen input on soil microbial community structure, soil nitrogen cycling, and the contents of nutrients in L. barbarum fruits. The structure and composition of the bacterial community in the rhizosphere soil of L. barbarum were significantly different under different nitrogen supply conditions, and high nitrogen addition inhibited the diversity and stability of bacterial communities. Low nitrogen input stimulated the relative abundance of ammonia-oxidizing bacteria (AOB), such as Nitrosospira, catalyzing the first step of the ammonia oxidation process. The results of the GLMM model showed that the level of nitrogen fertilizer (urea) input, the relative abundance of AOB, the relative abundance of Bradyrhizobium, and their combinations had significant effects on the soil nitrogen cycling and contents of nutrients in L. barbarum fruits. Therefore, we believe that moderately reducing the use of urea and other nitrogen fertilizers is more conducive to improving soil nitrogen use efficiency and Goji berry fruit quality by increasing the nitrogen cycling potential of soil microorganisms.

Effects of continuous cropping Jiashi muskmelon on rhizosphere microbial community

Introduction

The continuous cropping of crops can result in the deterioration of the soil environment and cause a decline in plant health and yield, which complicates agricultural production. However, the effects of continuous melon cropping on rhizospheric microbial communities remain poorly understood.

Methods

In this study, high-throughput absolute quantification 16S rRNA gene amplicon sequencing was employed to analyze the bacterial community structure of greenhouse rhizosphere soil from Jiashi muskmelon replanted for 0, 1, 2, and 3 years (CK, 1a, 2a, and 3a, respectively).

Results

The results showed that long- term continuous cropping caused significant changes in soil physicochemical properties. The bacterial absolute abundances increased, but the bacterial community richness and diversity were significantly lost (p < 0.05). The composition of bacterial community was more similar after 2 and 3 years of continuous cropping. The longer the continuous cropping years were, the greater the shift in the bacterial diversity and abundance. Analysis of potential functional components revealed that different bacterial groups were enriched in different continuous cropping years. The significant reduction of the taxa associated with nitrate reduction may be responsible for the loss of soil nitrogen in continuous cropping soil.

Discussion

In summary, continuous cropping had a significant impact on the bacterial community structure of Jiashi muskmelon rhizospheric soil, and these results will provide a reference for soil management and scientific fertilization of melon and other crops under a continuous cropping regime.

Structural characteristics and diversity of the rhizosphere bacterial communities of wild Fritillaria przewalskii Maxim. in the northeastern Tibetan Plateau

Introduction

Fritillaria przewalskii Maxim. is a Chinese endemic species with high medicinal value distributed in the northeastern part of the Tibetan Plateau. F. przewalskii root-associated rhizosphere bacterial communities shaped by soil properties may maintain the stability of soil structure and regulate F. przewalskii growth, but the rhizosphere bacterial community structure of wild F. przewalskii from natural populations is not clear.

Methods

In the current study, soil samples from 12 sites within the natural range of wild F. przewalskii were collected to investigate the compositions of bacterial communities via high-throughput sequencing of 16S rRNA genes and multivariate statistical analysis combined with soil properties and plant phenotypic characteristics.

Results

Bacterial communities varied between rhizosphere and bulk soil, and also between sites. Co-occurrence networks were more complex in rhizosphere soil (1,169 edges) than in bulk soil (676 edges). There were differences in bacterial communities between regions, including diversity and composition. Proteobacteria (26.47-37.61%), Bacteroidetes (10.53-25.22%), and Acidobacteria (10.45-23.54%) were the dominant bacteria, and all are associated with nutrient cycling. In multivariate statistical analysis, both soil properties and plant phenotypic characteristics were significantly associated with the bacterial community (p < 0.05). Soil physicochemical properties accounted for most community differences, and pH was a key factor (p < 0.01). Interestingly, when the rhizosphere soil environment remained alkaline, the C and N contents were lowest, as was the biomass of the medicinal part bulb. This might relate to the specific distribution of genera, such as Pseudonocardia, Ohtaekwangia, Flavobacterium (relative abundance >0.01), which all have significantly correlated with the biomass of F. przewalskii (p < 0.05).

Discussion

F. przewalskii is evidently averse to alkaline soil with high potassium contents, but this requires future verification. The results of the present study may provide theoretical guidance and new insights for the cultivation and domestication of F. przewalskii.

Effect of Parthenium hysterophorus L. Invasion on Soil Microbial Communities in the Yellow River Delta, China

Parthenium hysterophorus L., as an invasive plant, has negatively impacted the ecosystem functioning and stability of the terrestrial ecosystem in China. However, little information was available for its effects on microorganisms in the Yellow River Delta (YRD), the biggest newly-formed wetland in China. In the present study, high-throughput sequencing technology was used to obtain the bacterial community in soils and roots of different plant species, including P. hysterophorus and some native ones in the YRD. Our results showed that the Proteobacteria, Acidobacteriota, Gemmatimonadota, and Actinobacteriota were dominant in the rhizosphere soils of P. hysterophorus (84.2%) and Setaria viridis (86.47%), and the bulk soils (80.7%). The Proteobacteria and Actinobacteriota were dominant within the root of P. hysterophorus. A total of 2468 bacterial OTUs were obtained from different groups among which 140 were observed in all the groups; 1019 OTUs were shared by P. hysterophorus non-rhizosphere soil bacteria (YNR) P. hysterophorus rhizosphere soil bacteria (YRR) groups. The indexes of the ACE (823.1), Chao1 (823.19), Simpson (0.9971), and Shannon (9.068) were the highest in the YRR groups, showing the greatest bacterial community diversity. Random forest analysis showed that the Methylomirabilota and Dadabacteria (at the phylum level) and the Sphingomonas, and Woeseia (at the genus level) were identified as the main predictors among different groups. The LEfSe results also showed the essential role of the Acidobacteriota in the YRR group. The SourceTracker analysis of the bacterial community of the YRR group was mainly from GBS groups (average 53.14%) and a small part was from YNR groups (average 6.56%), indicating that the P. hysterophorus invasion had a more significant effect on native plants' rhizosphere microorganisms than soil microorganisms. Our observations could provide valuable information for understanding the bacterial diversity and structure of the soil to the invasion of P. hysterophorus.

Allelopathy and Allelochemicals of Solidago canadensis L. and S. altissima L. for Their Naturalization

Solidago canadensis L. and Solidago altissima L. are native to North America and have naturalized many other continents including Europa and Asia. Their species is an aggressive colonizer and forms thick monospecific stands. The evidence of the allelopathy for S. canadensis and S. altissima has accumulated in the literature since the late 20th century. The root exudates, extracts, essential oil and rhizosphere soil of S. canadensis suppressed the germination, growth and the arbuscular mycorrhizal colonization of several plants, including native plant species. Allelochemicals such as fatty acids, terpenes, flavonoids, polyphenols and their related compounds were identified in the extracts and essential oil of S. canadensis. The concentrations of total phenolics, total flavonoids and total saponins in the rhizosphere soil of S. canadensis obtained from the invasive ranges were greater than those from the native ranges. Allelochemicals such as terpenes, flavonoids, polyacetylene and phenols were also identified in the extracts, essential oil and the rhizosphere soil in S. altissima. Among the identified allelochemicals of S. altissima, the cis-dehydromatricaria ester may be involved in the allelopathy considering its growth inhibitory activity and its concentration in the rhizosphere soil. Therefore, the allelopathy of S. canadensis and S. altissima may support their invasiveness, naturalization and formation of thick monospecific stands. This is the first review article focusing on the allelopathy of both of S. canadensis and S. altissima.

Responses of Rhizosphere Bacterial and Fungal Communities to the Long-Term Continuous Monoculture of Water Oat

As an cultivated aquatic vegetable, the long-term continuous monocropping of water oat results in the frequent occurrence of diseases, the deterioration of ecological system and decreased quality of water oat. In this study, real-time quantitative PCR (qPCR) and Illumina high-throughput sequencing were used to determine the dynamic changes in bacterial and fungal communities in rhizosphere soil under continuous cropping of water oat for 1, 5, 10, 15 and 20 years (Y1, Y5, Y10, Y15 and Y20), and soil properties and enzyme activities were also determined. Results showed that the contents of soil organic carbon (SOC), total nitrogen (TN), alkali-hydrolyzable nitrogen (AN), available phosphorus (AP) and the activities of four soil enzymes increased in Y5 and Y10 and then decreased in Y15 and Y20. Spearman correlation analysis identified SOC, TN, AP and AN as the main factors that affect the four enzyme activities. The qPCR results showed that there was no significant difference in bacterial abundance between the different planting years, while the fungal abundance first increased and then decreased. The long-term continuous planting of water oat (Y15 and Y20) significantly reduced the operational taxonomic unit numbers and the Shannon, Chao1, and ACE indices of rhizosphere bacteria and fungi. The bacterial and fungal community compositions were markedly affected by the continuous planting year. The relative abundances of Bacteroidetes and Firmicutes decreased significantly in Y10 and Bacteroidetes increased significantly in Y15. Relative abundances of dominated Mortierellomycota and Ascomycota phyla increased with the continuous cropping years, while Rozellomycota presented the opposite trend. The AK, AN, and SOC were the main factors that changed the bacterial community, while AK and AP significantly shifted the fungal community. Thus, long-term continuous planting of water oat resulted in the deterioration of soil nutrients and microbial communities. The results provided a reference for the remediation of soil under continuous water oat planting and sustainable development of water oat industry.

Changes in soil fungal communities after onset of wheat yellow mosaic virus disease

Rhizosphere-associated microbes have important implications for plant health, but knowledge of the association between the pathological conditions of soil-borne virus-infected wheat and soil microbial communities, especially changes in fungal communities, remains limited. We investigated the succession of fungal communities from bulk soil to wheat rhizosphere soil in both infected and healthy plants using amplicon sequencing methods, and assessed their potential role in plant health. The results showed that the diversity of fungi in wheat rhizosphere and bulk soils significantly differed post wheat yellow mosaic virus disease onset. The structure differences in fungal community at the two wheat health states or two compartment niches were evident, soil physicochemical properties (i.e., NH4 +) contribute to differences in fungal community structure and alpha diversity. Comparison analysis showed Mortierellomycetes and Dothideomycetes as dominant communities in healthy wheat soils at class level. The genus Pyronemataceae and Solicoccozyma were significantly are significantly enriched in rhizosphere soil of diseased plant, the genus Cystofilobasidium, Cladosporium, Mortierella, and Stephanonectria are significantly enriched in bulk soil of healthy plant. Co-occurrence network analysis showed that the fungi in healthy wheat soil has higher mutual benefit and connectivity compared with diseased wheat. The results of this study demonstrated that the occurrence of wheat yellow mosaic virus diseases altered both fungal community diversity and composition, and that NH4 + is the most important soil physicochemical factor influencing fungal diversity and community composition.

Sex-based metabolic and microbiota differences in roots and rhizosphere soils of dioecious papaya (Carica papaya L.)

Dioecious plant species have a high genetic variation that is important for coping with or adapting to environmental stress through natural selection. Intensive studies have reported dimorphism morphism in morphology, physiology, as well as biotic and abiotic stress responses in dioecious plants. Here, we demonstrated the dimorphism of metabolic profile and the preference of some microorganisms in the roots and rhizosphere soils of male and female papaya. The metabolic composition of roots were significantly different between the males and females. Some sex hormones occurred in the differential metabolites in roots and rhizosphere soils. For example, testosterone was up-regulated in male papaya roots and rhizosphere soils, whereas norgestrel was up-regulated in the female papaya roots, indicating a possible balance in papaya roots to control the sexual differentiation. Plant hormones such as BRs, JAs, SA and GAs were also detected among the differential metabolites in the roots and rhizosphere soils of dioecious papaya. In addition, some metabolites that have medicinal values, such as ecliptasaponin A, crocin, berberine and sapindoside A were also expressed differentially between the two sexes. Numerous differential metabolites from the papaya roots were secreted in the soil, resulting in the differences in microbial community structure in the roots and rhizosphere soils. Some nitrogen-fixing bacteria such as Allorhizobium-Neorhizobium-Pararhizobium-Rhizobium, Brevundimonas and Microvirga were enriched in the male papaya roots or rhizosphere soils. While Candidatus Solibacter and Tumebacillus, which utilize organic matters, were enriched in the roots or rhizosphere soils of the female papaya. Some differences in the fungi abundance were also observed in both male and female papaya roots. These findings uncovered the effect of sex types on the metabolic and microbiota differences in roots and rhizosphere soils in papaya and will lead to investigations of underlining genomic and molecular mechanisms.

Long-term fertilization has different impacts on bacterial communities and phosphorus forms in sugarcane rhizosphere and bulk soils under low-P stress

The application of phosphorus (P) fertilizer effectively improves soil P availability, but it also affects soil microbial communities. However, the responses of soil bacterial communities and P forms to long-term P fertilization, and the relationships of bacterial communities with soil P forms remain unclear in P-deficient field. In this study, the impacts of different P fertilization treatments (chemical nitrogen and potassium (NK); chemical N, P and K (NPK); and NPK plus straw (NPKS)) on the bacterial communities and P forms in sugarcane rhizosphere (RS) and bulk soils (BS) were evaluated. Compared with the NK, the NPK and NPKS treatments significantly (P<0.05) increased the yield and quality characters of sugarcane, especially under NPKS. Additionally, P fertilization significantly increased the available P (AP), soluble inorganic P (Pi) and retained Pi in both the RS and BS, but they significantly increased the Chao1 and Shannon index only in the BS; and almost all these indices were significantly higher in the RS than in the BS. The bacterial community compositions were also significantly altered by P fertilization, with major changes in the RS and minor changes in the BS. The bacterial genera that were enriched in the sugarcane rhizosphere mainly included Bradyrhizobium, Rhodanobacter, Pseudolabrys, Conexibacter, and Burkholderia-Caballeronia-Paraburkholderia, some of which potentially promote the plant growth. Compared to NK, functional groups involved in the cycling of carbon, N, and sulfur significantly increased or decreased with fertilizer P application. Moreover, the relative abundances of many bacterial species were significantly correlated with the soil P forms. In conclusion, long-term P fertilization altered bacterial structure and functions in P-deficient sugarcane soil, which could help the soil P cycling and suppling. The results provide useful information to stimulate the power of the microbes by fertilization measures to improve soil nutrients and crop production.

Influence of plant genotype and soil on the cotton rhizosphere microbiome

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.

Host Plant Selection Imprints Structure and Assembly of Fungal Community along the Soil-Root Continuum

The soil fungal community plays pivotal roles in soil nutrient cycling and plant health and productivity in agricultural ecosystems. However, the differential adaptability of soil fungi to different microenvironments (niches) is a bottleneck limiting their application in agriculture. Hence, the understanding of ecological processes that drive fungal microbiome assembly along the soil-root continuum is fundamental to harnessing the plant-associated microbiome for sustainable agriculture. Here, we investigated the factors that shape fungal community structure and assembly in three compartment niches (the bulk soil, rhizosphere, and rhizoplane) associated with tobacco (Nicotiana tabacum L.), with four soil types tested under controlled greenhouse conditions. Our results demonstrate that fungal community assembly along the soil-root continuum is governed by host plant rather than soil type and that soil chemical properties exert a negligible effect on the fungal community assembly in the rhizoplane. Fungal diversity and network complexity decreased in the order bulk soil > rhizosphere > rhizoplane, with a dramatic decrease in Ascomycota species number and abundance along the soil-root continuum. However, facilitations (positive interactions) were enhanced among fungal taxa in the rhizoplane niche. The rhizoplane supported species specialization with enrichment of some rare species, contributing to assimilative community assembly in the rhizoplane in all soil types. Mortierella and Pyrenochaetopsis were identified as important indicator genera of the soil-root microbiome continuum and good predictors of plant agronomic traits. The findings provide empirical evidence for host plant selection and enrichment/depletion processes of fungal microbiome assembly along the soil-root continuum.

IMPORTANCE Fungal community assembly along the soil-root continuum is shaped largely by the host plant rather than the soil type. This finding facilitates the implementations of fungi-associated biocontrol and growth-promoting for specific plants in agriculture practice, regardless of the impacts from variations in geographical environments. Furthermore, the depletion of complex ecological associations in the fungal community along the soil-root continuum and the enhancement of facilitations among rhizoplane-associated fungal taxa provide empirical evidence for the potential of community simplification as an approach to target the plant rhizoplane for specific applications. The identified indicators Mortierella and Pyrenochaetopsis along the soil-root microbiome continuum are good predictors of tobacco plant agronomic traits, which should be given attention when manipulating the root-associated microbiome.

Variations in rhizosphere soil total phosphorus and bioavailable phosphorus with respect to the stand age in Pinus massoniana Lamb

Phosphorus (P) is a nutrient limiting plant growth in subtropical regions. However, our understanding of how soil P responds to an increase in stand age is rather poor. In particular, little is known about how bioavailable P pools (soluble P, exchangeable P, hydrolyzable P, and ligand P) shift with a change in stand age. Moreover, the P cycle in rhizosphere soil has the most direct and significant influence on plants. The aim of the present study was to determine the concentrations of total P in various rhizosphere soil bioavailable P fractions in 5-, 9-, 19-, 29-, and 35-year-old stands of Pinus massoniana Lamb. According to the results, total P (TP) concentration and N:P ratio in rhizosphere soil first decreased, and then increased with an increase in stand age. Soluble P concentration decreased first, and then increased with an increase in stand age; exchangeable P and ligand P decreased first, and then tended to be stable with an increase in stand age, whereas hydrolyzable P increased first, and then decreased. Structural Equation Model results suggested that ligand P and soluble P were the major factor affecting the TP. In addition, soil microorganisms and acid phosphatase-driven hydrolyzable P play a crucial role in soil bioavailable P cycling. Overall, the results of our study provide a mechanistic understanding of soil bioavailable P cycling under low available P conditions, and a basis for an effective P management strategy for the sustainable development of P. massoniana plantations.

Short-term Variability of Macro- and Trace Elements in Elymus Repens L. and Urtica Dioica L

BACKGROUND

The main aim of the research was to study short-term changes in the concentrations of elements in two widely distributed plant species, couch grass and nettle and in the rhizosphere soil of the plants.

METHODS

The sampling of plants and soil was carried out on three dates: 3, 10, and 25 May 2021. On each day of sampling, the plants and soil were collected three times: at 9:00, 14:00, and 19:00. The ICP-OES and ICP-MS analytical techniques were used for determination of elements in the plant and soil samples. The Raman spectroscopy was applied to study variations in the organic compounds.

RESULTS

The concentrations of both macro-nutrients and trace elements in plants varied greatly over daytime on all dates of sampling. The differences between concentrations of many elements in the plants collected at different times during a day were statistically significant. There were also statistically significant differences between concentrations of some elements (Na, Mg, P, K, Fe, Ba) in the plants collected on different dates. The relative intensity of diffuse luminescence of the rhizosphere soil of couch grass and nettle was different during daytime and also differed between the soils taken from roots of the two plant species, especially in the beginning of May.

CONCLUSIONS

The experimental data indicates that the daily variations of the element concentrations in plants might be a result of multiple effects of various factors. The differences in the daily element variations in the couch grass and nettle growing in the same site and collected simultaneously might be due to the fact that these plants belong to different clades. The diurnal fluctuations (that also include regular changes in the element concentrations in plants) can be different for monocotyledons (couch grass) and dicotyledons (nettle). New experimental findings on short-term variations in the concentrations of macro-nutrients and trace elements can help to gain a new insight into accumulation of the elements in different plant species and also be useful in agricultural practice.