Rhizosphere Microbial Community Structure Research Articles

Response of rhizosphere microbial community structure and production performance of corn and soybean to belt planting mode

Soybean and corn strip cropping takes full advantage of the root characteristics and plant height differences between soybean and corn, which can improve crop photosynthesis and nutrient uptake as well as capitalize on the marginal effect of corn. However, there is not enough in-depth research on the effects of soybean and corn strip cropping modes on inter-root microbial communities and crop yield traits and their correlations, and the functional genes of inter-root microbes. In this study, the structural composition and functional genes of soil inter-root microbial communities under different strip cropping patterns of soybean and maize, Mode 1, Mode 2, and Mode 3, were studied using macro-genome high-throughput sequencing, and the yield traits of soybean and maize were determined and the correlation was understood, taking Zhonglian Soybean 1505 and Tiyu 108 maize as test materials at the experimental base of the Research Institute of Agricultural and Livestock Sciences, Xing'anmeng, Inner Mongolia. correlation between the two. The following results were found. Redundancy analysis found that rhizosphere microorganisms are mainly bacteria, followed by viruses, followed by archaea, and fungi are the least. Relatively speaking, viruses and bacteria are more susceptible to the influence of planting patterns than fungi. Alpha diversity analysis shows that the diversity index changes significantly during the peak flowering period. There is no difference between the other two stages. The diversity of maize rhizosphere microorganisms under Mode 1 or Mode 2 modes is higher than that under Mode 3 modes, while the diversity of soybean rhizosphere microorganisms under Mode 3 modes is higher than the other two modes. Profiling analysis found that different growth periods and planting patterns lead to varying degrees of changes in community structure. The dominant bacterial phyla include Pseudomonas, Actinobacteria, Bacteroidetes, and Streptococcus. The dominant genera of bacteria are rhizobia, pseudomonas, erythrobacteria, and pseudomonas. The relative abundance of slow root rhizobia in the three growth stages of maize rhizosphere is relatively low. The results of yield traits showed that corn yield under Mode 1 and Mode 2 planting was significantly higher than that under pattern III; soybean yield under pattern III planting was significantly higher than that under the other two patterns, indicating that pattern I or II planting is suitable for corn production, while Mode 3 planting mode is more suitable for soybean production. Correlation analysis showed that S_Massilis_putida was significantly and positively correlated with maize yield, and S_lysobacter_capsici was highly significantly and significantly positively correlated with the number of soybean plants per square meter, and the number of plants in 2 square meters. This study contributes to our further understanding of the classification of inter-root microorganisms and their functional relationships in maize and soybean under different conditions.

Using multi-omics to explore the effect of Bacillus velezensis SAAS-63 on resisting nutrient stress in lettuce

To avoid the unreasonable use of chemical fertilizer, an environmentally friendly means of improving soil fertility is required. This study explored the role of the plant growth-promoting rhizosphere bacteria (PGPR) strain Bacillus velezensis SAAS-63 in improving nutrient stress in lettuce. Compared with no inoculation, B. velezensis SAAS-63 inoculants exhibited significantly increased fresh weight, root length, and shoot height under nutrient deficiency, as well as improved antioxidant activities and proline contents. The exogenous addition of B. velezensis SAAS-63 also significantly increased the accumulation of macroelements and micronutrients in lettuce. To elucidate the resistance mechanisms induced by B. velezensis SAAS-63 under nutrient stress, high-throughput sequencing and multi-omics analysis were performed. Inoculation with B. velezensis SAAS-63 altered the microbial community of the rhizosphere and increased the relative abundances of Streptomyces, Actinoallomurus, Verrucomicrobia, and Chloroflexi. It is worth noting that the inoculant SAAS-63 can affect plant rhizosphere metabolism. The inoculant changed the metabolic flow of phenylpropanoid metabolic pathway under nutrient deficiency and promoted phenylalanine to participate more in the synthesis of lignin precursors and coumarin substances by inhibiting the synthesis of flavone and isoflavone, thus improving plant resistance. This study showed that the addition of inoculant SAAS-63 could help plants recruit microorganisms to decompose and utilize trehalose and re-established the carbon metabolism of the plant rhizosphere. Additionally, microbes were found to be closely related to the accumulation of metabolites based on correlation analysis. The results indicated that the addition of PGPRs has an important role in regulating soil rhizosphere microbes and metabolism, providing valuable information for understanding how PGPRs affect complex biological processes and enhance plant adaptation to nutrient deficiency.Key points• Inoculation with SAAS-63 significantly promoted plant growth under nutrient-deficient conditions• Inoculation with SAAS-63 affected rhizosphere microbial diversity and community structure• Inoculation with SAAS-63 affected plant rhizosphere metabolism and induced plants to synthesize substances that resist stressGraphical abstract

The effect of white grub (Maladera Verticalis) larvae feeding on rhizosphere microbial characterization of aerobic rice (Oryza sativa L.) in Puer City, Yunnan Province, China

BackgroundRhizosphere microorganisms are vital in plants’ growth and development and these beneficial microbes are recruited to the root-zone soil when experiencing various environmental stresses. However, the effect of white grub (Maladera verticalis) larvae feeding on the structure and function of rhizosphere microbial communities of aerobic rice (Oryza sativa L.) is unclear.ResultsIn this study, we compared physicochemical properties, enzyme activities, and microbial communities using 18 samples under healthy and M. verticalis larvae-feeding aerobic rice rhizosphere soils at the Yunnan of China. 16 S rRNA and ITS amplicons were sequenced using Illumina high throughput sequencing. M. verticalis larvae feeding on aerobic rice can influence rhizosphere soil physicochemical properties and enzyme activities, which also change rhizosphere microbial communities. The healthy and M. verticalis larvae-feeding aerobic rice rhizosphere soil microorganisms had distinct genus signatures, such as possible_genus_04 and Knoellia genera in healthy aerobic rice rhizosphere soils and norank_f__SC − I−84 and norank_f__Roseiflexaceae genera in M. verticalis larvae-feeding aerobic rice rhizosphere soils. The pathway of the metabolism of terpenoids and polyketides and carbohydrate metabolism in rhizosphere bacteria were significantly decreased after M. verticalis larvae feeding. Fungal parasite–wood saprotroph and fungal parasites were significantly decreased after M. verticalis larvae feeding, and plant pathogen–wood saprotroph and animal pathogen–undefined saprotroph were increased after larvae feeding. Additionally, the relative abundance of Bradyrhizobium and Talaromyces genera gradually increased with the elevation of the larvae density. Bacterial and fungal communities significantly correlated with soil physicochemical properties and enzyme activities, respectively.ConclusionsBased on the results we provide new insight for understanding the adaptation of aerobic rice to M. verticalis larvae feeding via regulating the rhizosphere environment, which would allow us to facilitate translation to more effective measures.

Response of Phyllosphere and Rhizosphere Microbial Communities to Salt Stress of Tamarix chinensis.

As carriers of direct contact between plants and the atmospheric environment, the microbiomes of phyllosphere microorganisms are increasingly recognized as an important area of study. Salt secretion triggered by salt-secreting halophytes elicits changes in the community structure and functions of phyllosphere microorganisms, and often provides positive feedback to the individual plant/community environment. In this study, the contents of Na+ and K+ in the rhizosphere, plant and phyllosphere of Tamarix chinensis were increased under 200 mmol/L NaCl stress. The increase in electrical conductivity, Na+ and K+ in the phyllosphere not only decreased the diversity of bacterial and fungal communities, but also decreased the relative abundance of Actinobacteriota and Basidiomycota. Influenced by electrical conductivity and Na+, the bacteria-fungus co-occurrence network under salt stress has higher complexity. Changes in the structure of the phyllosphere microbial community further resulted in a significant increase in the relative abundance of the bacterial energy source and fungal pathotrophic groups. The relative abundance of Actinobacteriota and Acidobacteriota in rhizosphere showed a decreasing trend under salt stress, while the complexity of the rhizosphere co-occurrence network was higher than that of the control. In addition, the relative abundances of functional groups of rhizosphere bacteria in the carbon cycle and phosphorus cycle increased significantly under stress, and were significantly correlated with electrical conductivity and Na+. This study investigated the effects of salinity on the structure and physicochemical properties of phyllosphere and rhizosphere microbial communities of halophytes, and highlights the role of phyllosphere microbes as ecological indicators in plant responses to stressful environments.

Synergistic effects of rhizosphere effect and combined organic and chemical fertilizers application on soil bacterial diversity and community structure in oilseed rape cultivation.

The combined application of chemical and organic fertilizers has been recognized to enhance soil fertility and foster the soil microbial ecosystem. However, the optimal ratio of chemical and organic fertilizers in oilseed rape cultivation is still uncertain, and the role of rhizosphere effect is still unclear. Thus, this study aimed to elucidate the impacts of varying ratios of chemical and organic fertilizers on the structure and potential functionalities of rhizosphere and non-rhizosphere soil microbial communities. The interplay of microbial communities with soil properties and oilseed rape root exudates was investigated in controlled pot cultivations receiving varying ratios of chemical and organic fertilizers. Results indicated clear segregation in the soil bacterial community, influenced by both fertilization treatments and rhizosphere effects. The bacterial community structure significantly correlated with nitrate nitrogen, organic acids, and dissolved organic carbon (DOC) content. Rhizosphere effects led to increased bacteria abundance, reduced diversity, and decreased network stability. Notably, F3 treatment receiving 25% chemical and 75% organic fertilizers showed a significantly higher abundance at 1.43 × 1011 copies g-1 dry soil, accompanied by increased species and genetic diversity, and ecological network complexity. This treatment also yielded the highest aboveground biomass of oilseed rape. However, the application of organic fertilizers also increased the risk of plant pathogenicity. This study reveals the impact of fertilizers and rhizosphere effects on soil microbial community structure and function, shedding light on the establishment of more effective fertilization schemes for oilseed rape agriculture.

Nitrogen fertilization practices alter microbial communities driven by clonal integration in Moso bamboo

Nitrogen (N) fertilization is crucial for maintaining plant productivity. Clonal plants can share resources between connected ramets through clonal integration influencing microbial communities and regulating soil biogeochemical cycling, especially in the rhizosphere. However, the effect of various N fertilization practices on microbial communities in the rhizosphere of clonal ramets remain unknown. In this study, clonal fragments of Moso bamboo (Phyllostachys edulis), consisting of a parent ramet, an offspring ramet, and an interconnecting rhizome, were established in the field. NH4NO3 solution was applied to the parent, offspring ramets or rhizomes to investigate the effect of fertilization practices on the structure and function of rhizosphere microbial communities. The differences in N availability, microbial biomass and community composition, and abundance of nitrifying genes among rhizosphere soils of ramets gradually decreased during the rapid growth of Moso bamboo, irrespective of fertilization practice. The soil N availability variation, particularly in NO3−, caused by fertilization practices altered the rhizosphere microbial community. Soil N availability and stable microbial biomass N in parent fertilization were the highest, being 9.0 % and 18.7 %, as well as 60.8 % and 90.4 % higher than rhizome and offspring fertilizations, respectively. The microbial network nodes and links in rhizome fertilization were 1.8 and 7.5 times higher than in parent and offspring fertilization, respectively. However, the diversity of bacterial community and abundance of nitrifying and denitrifying genes were the highest in offspring fertilization among three practices, which may be associated with increased N loss. Collectively, the rhizosphere microbial community characteristics depended on fertilization practices by altering the clonal integration of N in Moso bamboo. Parent and rhizome fertilization were favorable for N retention in plant-soil system and resulted in more stable microbial functions than offspring fertilization. Our findings provide new insights into precision fertilization for the sustainable Moso bamboo forest management.

A Synthetic Microbiome Based on Dominant Microbes in Wild Rice Rhizosphere to Promote Sulfur Utilization

Sulfur (S) is one of the main components of important biomolecules, which has been paid more attention in the anaerobic environment of rice cultivation. In this study, 12 accessions of rice materials, belonging to two Asian rice domestication systems and one African rice domestication system, were used by shotgun metagenomics sequencing to compare the structure and function involved in S cycle of rhizosphere microbiome between wild and cultivated rice. The sulfur cycle functional genes abundances were significantly different between wild and cultivated rice rhizosphere in the processes of sulfate reduction and other sulfur compounds conversion, implicating that wild rice had a stronger mutually-beneficial relationship with rhizosphere microbiome, enhancing sulfur utilization. To assess the effects of sulfate reduction synthetic microbiomes, Comamonadaceae and Rhodospirillaceae, two families containing the genes of two key steps in the dissimilatory sulfate reduction, aprA and dsrA respectively, were isolated from wild rice rhizosphere. Compared with the control group, the dissimilatory sulfate reduction in cultivated rice rhizosphere was significantly improved in the inoculated with different proportions groups. It confirmed that the synthetic microbiome can promote the S-cycling in rice, and suggested that may be feasible to construct the synthetic microbiome step by step based on functional genes to achieve the target functional pathway. In summary, this study reveals the response of rice rhizosphere microbial community structure and function to domestication, and provides a new idea for the construction of synthetic microbiome.

The Effect of Bacillus velezensis LJ02 Compounded with Different Fungi on the Growth of Watermelon Seedlings and Microbial Community Structure

The application of beneficial microbial consortium can effectively improve plant disease resistance and its growth. Various fungi were compounded with Bacillus velezensis LJ02 and applied to watermelon plants in this paper. The results showed that the microbial consortium T2 (compounded Bacillus velezensis LJ02 with Aspergillus aculeatus 9) can effectively control gummy stem blight and powdery mildew in watermelon, while the control effect reached 83.56% and 70.93%, respectively (p < 0.05). Compound treatment improved the diversity and richness of the rhizosphere microbial community structure, and the relative abundance of Caulobacterales and Xanthomonadaceae significantly increased after applying T2 to the soil. Meanwhile, the internode length was significantly decreased 28% (p < 0.05), and the maximum leaf length increased 10.33% (p < 0.05). In addition, the microbial consortium delays the maturity of watermelon vegetables. By studying the effects of microbial consortium on watermelon seedlings, our study provides a theoretical basis for the popularization and application of the compound inoculant.

Effects of plant growth-promoting rhizobacteria on blueberry growth and rhizosphere soil microenvironment.

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

Straw and Biochar Application Alters the Structure of Rhizosphere Microbial Communities in Direct-Seeded Rice (Oryza sativa L.) Paddies

A comprehensive understanding of rice straw (RS) and biochar (BC) addition affecting soil quality, enzyme activities, bacterial community structure and grain yield is crucial. The objective of this study was to examine the dynamics of the soil microbial community impacted by the application of rice straw and biochar, and to understand the relationship between the microbial communities, soil enzymes, nutrients and grain yield of paddies. We conducted a field experiment with organic amendments under the direct seeding of paddies. The bacterial community structure in the rhizosphere was characterized using high-throughput 16S rRNA sequencing. The results showed that RS amendment increased grain yields by 8.5 and 9.9% more than with BC and the control without organic amendment (CK), respectively (p < 0.05). The abundance of bacteria associated with nitrate reduction in RS was higher than that in BC and CK, which further showed the significance of the RS-treated soil bacteria in rice nutrient utilization. A cladogram plotted using linear discriminant analysis effect size showed that Proteobacteria (Alphaproteobacteria), Acidobacteria, Firmicutes, Verrucomicrobia and Epsilonbacteraeota in the RS-treated soil increased in comparison with CK. Pearson’s correlation analysis showed that enzymes activities (cellulase activity and protease activity), soil nutrition content (soil hydrolyzable nitrogen), and bacterial phyla (Nitrospinae) were positively correlated with grain yield, suggesting that the RS-treated soil improved enzyme activities, soil nutrition content, and bacterial abundance, which in turn increased grain yield. The results indicated that RS-treated bacterial communities combined with soil enzymatic activities strengthen the transformation of nutrients, suggesting that the interactions play an important role in enhancing the grain yield of paddy rice. These results provide new insights and a theoretical basis for studying the changes in soil microbial communities with the application of RS and BC in Northeastern China.

Response of rhizosphere soil physicochemical properties and microbial community structure to continuous cultivation of tobacco

PurposeThe health of rhizosphere soil microorganisms is an important indicator to evaluate soil quality. Therefore, understanding the response of rhizosphere soil microorganisms to tobacco crop succession is crucial for promoting the sustainable development of agriculture.MethodsThe microbial diversity and community structure of rhizosphere soil in continuous cropping and non-cropped tobacco for 7 years were analyzed by the Illumina platform.Result(1) Continuous cropping tobacco cause rhizosphere soil acidification and reduction in alkaline nitrogen (AN) and soil organic matter (SOM). (2) Continuous cropping tobacco reduces the diversity of rhizosphere soil microbial communities, increasing harmful functional microorganisms and declining beneficial ones. (3) The abundance of bacteria that perform nitrification and saprophytic fungi in the rhizosphere soil of continuous cropping areas decreases, inhibiting carbon and nitrogen cycling processes. (4) The composition and diversity of the soil rhizosphere microbial community are affected by the imbalance in the physicochemical property of the rhizosphere.ConclusionContinuous cropping tobacco cause rhizosphere soil acidification and nutrient imbalance, and the carbon and nitrogen cycles involved in microorganisms were damaged. Furthermore, the decreased diversity of rhizosphere soil microorganisms and the increased abundance of pathogenic fungi contribute to the continuous cropping obstacles of tobacco.

Response of Soil Microorganisms and Phenolic to Pseudostelariae heterophylla Cultivation in Different Soil Types

Pseudostellaria heterophylla of the Caryophyllaceae family is an important medicinal herb in traditional Chinese medicine, but it encounters continuous cropping obstacle during cultivation. This study aimed to study the differences in the response of Pseudostellaria heterophylla cultivation to soil microorganisms and phenolic substances in different types of soil (Loamy soil and Clayey soil). The analysis of soil metabolites using HPLC-ESI-Q/TOF-MS and HPLC-DAD techniques revealed that the content of various phenolic components in the rhizosphere soil increased significantly after Pseudostellaria heterophylla cultivation. Pseudostellaria heterophylla cultivation in yellow soil could increase the abundance of Proteobacteria, Ascomycota, and Thermoplasmatota, while in brown soil, the abundance of Ascomycota significantly decreased. In addition, Pseudostellaria heterophylla cultivation could increase the α-diversity of bacteria and fungi in yellow soil, while reducing the α-diversity of archaea, and the impact on diversity in brown soil was relatively small. Correlation analysis showed that phenolic compounds were more likely to regulate the genera Bradyrhizobium, Calcarisporiella, Boothiomyces and Methanocella. Pseudostellaria heterophylla may regulate rhizosphere microbial diversity and community structure by secreting phenolic. However, in different types of soil environments, the response mechanism of soil microorganisms to Pseudostellaria heterophylla planting might vary. Our study provides new insights that the variability in the response of different soil types to Pseudostelariae heterophylla cultivation should be taken into account when developing strategies for reducing continuous cropping obstacles in medicinal plants.

Effects of polystyrene, polyethylene, and polypropylene microplastics on the soil-rhizosphere-plant system: Phytotoxicity, enzyme activity, and microbial community

The widespread presence of soil microplastics (MPs) has become a global environmental problem. MPs of different properties (i.e., types, sizes, and concentrations) are present in the environment, while studies about the impact of MPs having different properties are limited. Thus, this study investigated the effects of three common polymers (polystyrene, polyethylene, and polypropylene) with two concentrations (0.01% and 0.1% w/w) on growth and stress response of lettuce (Lactuca sativa L.), soil enzymes, and rhizosphere microbial community. Lettuce growth was inhibited under MPs treatments. Moreover, the antioxidant system, metabolism composition, and phyllosphere microbiome of lettuce leaves was also perturbed. MPs reduced phytase activity and significantly increased dehydrogenase activity. The diversity and structure of rhizosphere microbial community were disturbed by MPs and more sensitive to polystyrene microplastics (PSMPs) and polypropylene microplastics (PPMPs). In general, the results by partial least squares pathway models (PLS-PMs) showed that the presence of MPs influenced the soil-rhizosphere-plant system, which may have essential implications for assessing the environmental risk of MPs.

Arbuscular mycorrhizal fungi increased peanut (Arachis hypogaea L.) yield by changing the rhizosphere microbial community structure in saline-alkali soil.

Arbuscular mycorrhizal fungi (AMF) have demonstrated the potential to enhance the saline-alkali tolerance in plants. Nevertheless, the extent to which AMF can ameliorate the tolerance of salt-sensitive plants to alkaline conditions necessitates further investigation. The current study is primarily centered on elucidating the impact of AMF on the growth of the Huayu22 (H22) when cultivated in saline-alkaline soil. We leveraged DNA of rhizosphere microorganisms extracted from saline-alkali soil subjected to AMF treatment and conducted high-throughput sequencing encompassing 16S rRNA gene and ITS sequencing. Our findings from high-throughput sequencing unveiled Proteobacteria and Bacillus as the prevailing phylum and genus within the bacterial population, respectively. Likewise, the predominant fungal phylum and genus were identified as Ascomycota and Haematonectria. It is noteworthy that the relative abundance of Proteobacteria, Actinobacteria, Chloroflexi, Bacteroidetes, and Ascomycota exhibited significant increments subsequent to AMF inoculation. Our investigation into soil enzyme activity revealed a remarkable surge post-AMF inoculation. Notably, the amounts of pathogen growth inhibitory enzymes and organic carbon degrading enzymes rise, as predicted by the putative roles of microbial communities. In saline-alkali soil, inoculation of AMF did boost the yield of H22. Notable improvements were observed in the weight of both 100 fruits and 100 grains, which increased by 20.02% and 22.30%, respectively. Conclusively, this study not only provides a theoretical framework but also furnishes empirical evidence supporting the utilization of AMF as a viable strategy for augmenting the yield of salt-sensitive plants grown in alkaline conditions.

Improvement in gravel-mulched land soil nutrient and bacterial community diversity with Lonicera japonica.

Gravel-mulched land in China suffers from poor natural resources and fragile ecological environment, posing a challenge to effective restoration of ecological function. Lonicera japonica, a traditional Chinese herb used for treating human diseases, is a highly adaptable and resilient plant species, can effectively improve the soil properties, and may have important implications for the ecology and economy of gravel-mulched land. A study was conducted in a gravel-mulched field to measure the impact of planting the L. japonica (including control (CK), 1-year, 2-year, and 4-year cultivation of plants) on (i) dynamic changes in soil nutrient and enzyme activity properties, and (ii) soil rhizosphere microbial community structure characteristics. We found that the concentration of soil organic carbon, available nitrogen, available phosphorus and available potassium in L. japonica soil after cultivation for 1-4 years increased by 11-409%. The urease, phosphatase and catalase activities were increased by 11-560%, with the highest nutrient concentration and enzyme activity in 4-year plants. The pH value gradually decreased after cultivation. The improved soil environments increased soil bacterial community diversity. Planting L. japonica significantly increased the bacterial ACE, Chao1 index, Simpson index, and Shannon-Wiener index. The Firmicutes, Proteobacteria and Bacteroidetes were observed in dominant phyla. The relative abundance of eight genera, including Streptococcus, Veillonella and Rothia, was significantly reduced by more than 1%. Taken together, these soil indicators suggest that planting L. japonica in the short term would be a cost-effective strategy to combat soil degradation in a gravel-mulched ecosystem.

Alfalfa Plant Age (3 to 8 Years) Affects Soil Physicochemical Properties and Rhizosphere Microbial Communities in Saline–Alkaline Soil

Increasing soil salinization can severely restrict local agricultural production. Planting alfalfa is considered an effective measure to ameliorate saline–alkali soil. However, it remains unclear how alfalfa planting years affect the sustained impact on soil and rhizosphere microecology. This study analyzed the effects of alfalfa planted 3, 6, and 8 years ago on soil physicochemical properties and key soil enzyme activities and investigated the rhizosphere microbial community structure and diversity. The results indicate that cultivating alfalfa plants for six years can improve soil physicochemical properties and enhance soil fertility to a certain extent. This is attributed to a higher abundance of plant growth-promoting bacteria, such as Bradyrhizobium and Allorhizobium, as well as degradation bacteria, such as Flavobacterium, Stenotrophomonas, Brevundimonas, and Massilia, in the rhizosphere of alfalfa plants. These microorganisms promote alfalfa growth, improve soil quality, and inhibit the accumulation of autotoxins. This not only maintains high alfalfa yields but also optimizes soil physicochemical properties and enzyme activity, facilitating more effective nutrient cycling and metabolic processes in the soil. However, extending plant growth to 8 years is not beneficial.

Rhizosphere microbial ecological characteristics of strawberry root rot.

Strawberry (Fragaria × ananassa Duch.) holds a preeminent position among small fruits globally due to its delectable fruits and significant economic value. However, strawberry cultivation is hampered by various plant diseases, hindering the sustainable development of the strawberry industry. The occurrence of plant diseases is closely linked to imbalance in rhizosphere microbial community structure. In the present study, a systematic analysis of the differences and correlations among non-culturable microorganisms, cultivable microbial communities, and soil nutrients in rhizosphere soil, root surface soil, and non-rhizosphere soil of healthy and diseased strawberry plants affected by root rot was conducted. The goal was to explore the relationship between strawberry root rot occurrence and rhizosphere microbial community structure. According to the results, strawberry root rot altered microbial community diversity, influenced fungal community composition in strawberry roots, reduced microbial interaction network stability, and enriched more endophytic-phytopathogenic bacteria and saprophytic bacteria. In addition, the number of bacteria isolated from the root surface soil of diseased plants was significantly higher than that of healthy plants. In summary, the diseased strawberry plants changed microbial community diversity, fungal species composition, and enriched functional microorganisms significantly, in addition to reshaping the microbial co-occurrence network. The results provide a theoretical basis for revealing the microecological mechanism of strawberry root rot and the ecological prevention and control of strawberry root rot from a microbial ecology perspective.

Rhizosphere microbial community structure differs between constant subzero and freeze-thaw temperature regimes in a subarctic soil.

In the Arctic and subarctic, climate change is causing reduced snowpack extent and earlier snowmelt. Shallower snowpack decreases the thermal insulation of underlying soil and results in more freeze-thaw conditions reflective of dynamic air temperatures. The aim of this study was to determine the effect of alternative temperature regimes on overall microbial community structure and rhizosphere recruitment across representatives of three subarctic plant functional groups. We hypothesized that temperature regime would influence rhizosphere community structure more than plant type. Planted microcosms were established using a tree, forb, grass, or no plant control and subjected to either freeze-thaw cycling or static subzero temperatures. Our results showed rhizosphere communities exhibited reduced diversity compared to bulk soils, and were influenced by temperature conditions and to a lesser extent plant type. We found that plants have a core microbiome that is persistent under different winter temperature scenarios but also have temperature regime-specific rhizosphere microbes. Freeze-thaw cycling resulted in greater community shifts from the pre-incubation soils when compared to constant subzero temperature. This finding suggests that wintertime snowpack conditions may be a significant factor for plant-microbe interactions upon spring thaw.

Microbial communities and functions changed in rhizosphere soil of Pinus massoniana provenances with different carbon storage.

The average carbon storage of Pinus massoniana is much higher than the average carbon storage of Chinese forests, an important carbon sink tree species in subtropical regions of China. However, there are few studies on the differences in rhizosphere microorganisms of P. massoniana with different carbon storages. To clarify the relationships between plant carbon storage level, environmental parameters and microbial community structure, we identified three carbon storage levels from different P. massoniana provenances and collected rhizosphere soil samples. We determined chemical properties of soil, extracellular enzyme activity, and microbial community structures at different carbon storage levels and examined how soil factors affect rhizosphere microorganisms under different carbon storage levels. The results revealed that soil organic carbon (SOC), nitrate nitrogen (NO3--N), ammonium nitrogen (NH4+-N) contents all increased with increasing carbon storage levels, while pH decreased accordingly. In contrast, the available phosphorus (AP) content did not change significantly. The soil AP content was within the range of 0.91 ~ 1.04 mg/kg. The microbial community structure of P. massoniana changed with different carbon storage, with Acidobacteria (44.27%), Proteobacteria (32.57%), and Actinobacteria (13.43%) being the dominant bacterial phyla and Basidiomycota (73.36%) and Ascomycota (24.64%) being the dominant fungal phyla across the three carbon storage levels. Soil fungi were more responsive to carbon storage than bacteria in P. massoniana. C/N, NH4+-N, NO3--N, and SOC were the main drivers (p < 0.05) of changes in rhizosphere microbial communities. The results revealed that in the rhizosphere there were significant differences in soil carbon cycle and microorganism nutrient preferences at different carbon storages of P. massoniana provenance, which were significantly related to the changes in rhizosphere microbial community structure. Jiangxi Anyuan (AY) provenance is more suitable for the construction of high carbon storage plantation.

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.