Diversity In Rhizosphere Soil Research Articles

Combined effects of border irrigation and super-absorbent polymers on enzyme activity and microbial diversity of poplar rhizosphere soil.

Fast-growing poplar plantations are considered a great benefit to timber production, but water availability is a key factor limiting their growth and development, especially in arid and semi-arid ecosystems. Super-absorbent polymers facilitate more water retention in soil after rain or irrigation, and they are able to release water gradually during plant growth. This study aimed to examine the effects of reduced irrigation (60% and 30% of conventional border irrigation) co-applied with super-absorbent polymers (0, 40 kg/ha) on root exudates, enzyme activities, microbial functional diversity in rhizosphere soil, and volume increments in poplar (Populus euramericana cv. 'Neva'). The results showed that 60% border irrigation co-applied with super-absorbent polymers significantly increased the content of organic acids, amino acids and total sugars in the root exudates, and the activities of invertase, urease, dehydrogenase, and catalase in the rhizosphere soil in comparison to conventional border irrigation without super-absorbent polymers. Meanwhile, this treatment also enhanced the average well-color development, Shannon index, and McIntosh index, but decreased the Simpson index. Additionally, the average volume growth rate and relative water content of leaves reached their maximum using 60% irrigation with super-absorbent polymers, which was significantly higher than other treatments. However, using 30% irrigation with super-absorbent polymers, had a smaller effect on rhizosphere soil and volume growth than 60% irrigation with super-absorbent polymers. Therefore, using an appropriate water-saving irrigation measure (60% conventional border irrigation with super-absorbent polymers) can help to improve enzyme activities and microbial diversity in the rhizosphere soil while promoting the growth of poplar trees.

Analysis of Microbial Diversity in Rhizosphere Soil of Panax notoginseng under Different Water and Microbial Fertilizer Conditions

Panax notoginseng is a highly regarded medicinal plant that has obstacles associated with continuous cropping. Understanding soil microorganisms is crucial, as they play a major role in this regard. However, soil microorganisms are affected by multiple factors; therefore, we need to conduct more in-depth research. This study investigated the combined effects of irrigation and microbial fertilizer treatments (J1F1, J1F2, J2F1, J2F2, J3F1, J3F2, and CK) on the diversity of bacterial and fungal microbial communities in the rhizosphere of Panax notoginseng. The bacterial 16S rRNA genes and fungal internal transcribed spacer (ITS) sequences were sequenced using Illumina HiSeq. The results showed that, without microbial fertilizer (CK), the microbial community abundance and diversity were significantly lower than in the other treatments; moreover, among the microbial fertilizer treatments, the microbial abundance in F1 was higher than that in F2. Under the same microbial fertilizer application, the incidence rate of Panax notoginseng root rot was J2 > J1 > J3, and the yield of Panax notoginseng was J3 > J2 > J1. Under the same irrigation conditions, the incidence rate of Panax notoginseng root rot was F1 > F2, and the yield of Panax notoginseng was F2 > F1. This study provides important guidance for Panax notoginseng plant microbiota and sustainable agriculture.

Elevated Altitude and Limestone Soil Promoted Fungal Diversity in Rhizosphere Soil of Sophora japonica

Soil microorganisms play a crucial role in mediating material transformation and nutrient cycling. However, little attention has been paid to the relationships between microbial communities and altitude and lithology in karst regions. Sophora japonica cv. Jinhuai is an officinal plant cultivated in karst areas, and there is a correlation between the dynamics of microbial community and ecological factors. This study examined the diversity of microbial communities in the rhizosphere of S. japonica under different lithologies and altitudes in karst regions of northern Guangxi, China using high-throughput sequencing technology. It was found that the bacterial community consisted of 37 phyla, including Proteobacteria. The fungal community mainly comprised 15 phyla, including Ascomycota. The fungal Shannon and Chao1 indices increased with altitude, while the bacterial Shannon index decreased. The fungal Shannon indices in limestone soil were higher than those in dolomite. The soil’s microbial Shannon and Chao1 indices were positively affected by pH, while the available phosphorus and potassium had the opposite effect. Research shows that altitude, lithology, pH, and available phosphorus were the crucial factors influencing the rhizosphere soil microbial community. This study provides references for understanding the relationship between plants and microorganisms and the microbial distribution strategy of rocky desertification habitats in the future.

Ridge-furrow planting patterns with film mulching improve water use efficiency by enhancing arbuscular mycorrhizal fungi in the rhizosphere and endophyte of summer maize

In a rainfed agroecosystem with limited water resources, the symbiotic interactions between crop-arbuscular mycorrhizal fungi may have a significant impact on field productivity and water absorption and utilization. However, the interaction between AMF characteristics of root endophyte and rhizosphere soil and water use patterns of summer maize has not been studied under ridge-furrow with film mulching planting patterns (RFPM) in dry farmland. Based on a field experiment, we aimed to reveal the effects of different RFPM planting patterns (i.e., ridge/furrow ratio of 40:70 cm (RF40:70), ridge/furrow ratio of 55:55 cm (RF55:55), and ridge/furrow ratio of 70:40 cm (RF70:40)) on the root water use patterns of summer maize, the distribution characteristics of AMF in root endophyte and rhizosphere soil, and their interaction relationship by using the water isotope (δD and δ18O) tracer technique, the high-throughput sequencing technology, MixSIAR model, and the structural equation models. As a result, compared to flat planting without mulching (FP), RF40:70, RF55:55, and RF70:40 significantly increased grain yield by 29.74%, 35.24%, and 45.53%, and water use efficiency by 23.13%, 35.99%, and 50.25%, across the two growing seasons, respectively (P < 0.05). The root characteristic parameters of summer maize decreased with the increase in soil depth, and were mainly distributed in the shallow layer (0–20 cm) and middle layer (20–60 cm). Compared with FP, the distribution ratio of root surface area density, root length density, and root dry weight density in shallow soil layer was significantly increased by 5.03%, 7.46%, and 9.70% averaging the different RFPM treatments, respectively (P<0.05). Besides, compared to FP, the AMF abundance and diversity in rhizosphere soil and root endogenous averaged RFPM treatments increased by 32.32% and 29.66% and 5.88% and 28.43% respectively, in which the abundance and diversity gradually increased with the increase of the ratio of ridge-furrow. The PLS-PM results found that the larger ridge-furrow ratio could significantly increase the yield and WUE of summer maize mainly by increasing the root surface area density, root length density, and the abundance and diversity of AMF in the root endophyte and rhizosphere soil, which increased the water use of the middle and deep layer soils. In summary, the large ridge-furrow ratio can significantly increase the yield and WUE of summer maize by extending the hyphal network of maize root symbiotic AMF, which increases the water uptake of middle and deep layer soil.

Fertility and microbial diversity in rhizosphere soil of Camellia oleifera under different intercropping systems

Fertility and microbial diversity in rhizosphere soil of Camellia oleifera under different intercropping systems

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.

Influences of phosphorus-modified biochar on bacterial community and diversity in rhizosphere soil.

Root-associated bacteria play a vital role in the soil ecosystem and plant productivity. Previous studies have reported the decline of bacterial community and rhizosphere soil quality in the cultivation of some medicinal plants (i.e., Pseudostellaria heterophylla). Phosphorus (P)-modified biochar has the potential to improve soil health and quality. However, its influence on the bacterial community and diversity in the rhizosphere of medicinal plants is not well understood. Therefore, this study aims to investigate the effects of P-modified biochar on the bacterial community and diversity in the rhizosphere of P. heterophylla. Soil samples were collected from the rhizosphere of 4-month P. heterophylla under control (no biochar), 3% unmodified and 3% P-modified biochar treatments, respectively. Compared with control and unmodified biochar treatment, P-modified biochar significantly increased the relative abundance of plant-beneficial bacteria (P < 0.05), particularly Firmicutes, Nitrospirae and Acidobacteria. The relative abundance of Bacillus, belonging to Firmicutes, was dramatically raised from 0.032% in control group to 1.723% in P-modified biochar-treated group (P < 0.05). These results indicate the potential enhancement of soil quality for the growth of medicinal plants. The application of biochar significantly increased bacterial richness and bacterial diversity (P < 0.05). P modification of biochar did not have significant effects on soil bacterial richness (P > 0.05), while it reduced Shannon and increased Simpson diversity index of soil bacterial communities significantly (P < 0.05). It indicates a decrease in bacterial diversity. This research provides a new perspective for understanding the role of P-modified biochar in the rhizosphere ecosystem.

Community Structure and Diversity of Rhizosphere Soil and Endophytic Bacteria during the Period of Growth of Moso Bamboo Shoots.

The purpose of this study was to elucidate the community structure of rhizosphere soil bacteria and endophytic bacteria during the growth of moso bamboo (Phyllostachys edulis) shoots. This study collected the rhizospheric soil samples, tissue samples of rhizome roots, shoot buds, winter bamboo shoots, spring bamboo shoots, and samples of forest soil. Their metagenomic DNA was extracted, and the bacterial community structure and diversity characteristics were compared and analyzed using high-throughput sequencing technology. These samples enabled the identification of 32 phyla, 52 classes, 121 orders, 251 families, and 593 genera of bacteria. The phyla primarily included Proteobacteria, Acidobacteria, and Cyanobacteria among others. Proteobacteria was the dominant phylum in the samples of bamboo shoots and rhizome roots, whereas Acidobacteria was dominant in the rhizosphere and forest soil samples. The predominant genera of the rhizome root samples were Acidothermus, Bradyrhizobium and Acidobacterium, and the predominant genera of the soil samples were Acidothermus and Acidobacterium. This study preliminarily revealed the regularity between the growth and development of bamboo shoots and the changes in the community structure of rhizosphere soil and endophytic bacteria, which provides insights into the relationship between growth and the bacterial community structure in different stages of bamboo shoots.

Intercropping system modulated soil-microbe interactions that enhanced the growth and quality of flue-cured tobacco by improving rhizospheric soil nutrients, microbial structure, and enzymatic activities.

As the promotive/complementary mechanism of the microbe-soil-tobacco (Nicotiana tabacum L.) interaction remains unclear and the contribution of this triple interaction to tobacco growth is not predictable, the effects of intercropping on soil nutrients, enzymatic activity, microbial community composition, plant growth, and plant quality were studied, and the regulatory mechanism of intercropping on plant productivity and soil microenvironment (fertility and microorganisms) were evaluated. The results showed that the soil organic matter (OM), available nitrogen (AN), available phosphorus (AP), available potassium (AK), the urease activity (UE) and sucrase activity (SC), the diversity, abundance, and total and unique operational taxonomic units (OTUs) of bacteria and fungi as well as plant biomass in T1 (intercropping onion), T2 (intercropping endive), and T3 (intercropping lettuce) treatments were significantly higher than those of the controls (monocropping tobacco). Although the dominant bacteria and fungi at the phylum level were the same for each treatment, LEfSe analysis showed that significant differences in community structure composition and the distribution proportion of each dominant community were different. Proteobacteria, Acidobacteria, and Firmicutes of bacteria and Ascomycota and Basidiomycetes of fungi in T1, T2, and T3 treatments were higher than those of the controls. Redundancy analysis (RDA) suggested a close relation between soil characteristic parameters and microbial taxa. The correlation analysis between the soil characteristic parameters and the plant showed that the plant biomass was closely related to soil characteristic parameters. In conclusion, the flue-cured tobacco intercropping not only increased plant biomass and improved chemical quality but also significantly increased rhizospheric soil nutrient and enzymatic activities, optimizing the microbial community composition and diversity of rhizosphere soil. The current study highlighted the importance of microbe-soil-tobacco interactions in maintaining plant productivity and provided the potential fertilization practices in flue-cured tobacco production to maintain ecological sustainability.

Composition, function and driving factors of microbial communities in rhizosphere soil and root endophyte of Codonopsis pilosula in different years

Root microbial communities influence plant health and response to environmental stress. While the succession of rhizosphere soil and endophytic microbial communities in the growth stage of perennial medicinal plant Codonopsis pilosula remains unclear. In this study, rhizosphere soil and root tissue samples of one-year, two-year and three-year C. pilosula were selected to determine the community composition and diversity of rhizosphere soil and root endophyte microorganisms based on high-throughput sequencing technology. The results showed that the composition and structure of microbial community in rhizosphere soil and root endophyte of C. pilosula were different in different planting years. The abundance of Proteobacteria has decreased significantly, while that of Acidobacteria and Ascomycota have increased significantly. The neutral community model showed that the bacteria were mainly affected by random assembly and fungi by deterministic assembly. The complexity of microbial network in rhizosphere soil was higher than that in the root endophyte, and the complexity of bacterial network was higher than that of fungal community. Environmental factors significantly affected the microbial diversity of C. pilosula root system, while the growth years had little effect on it. Soil protease (PRO), soil total nitrogen (TN) and microbial biomass carbon (MBC) were the key factors causing the changes of C. pilosula microbiome. This study provides insights into the dynamic changes and driving factors of root microbial community of C. pilosula, and provides a basis for regulating root microbial community in C. pilosula cultivation to improve the sustainability of agricultural production.

Bacterial Communities Structure and Diversity in Rhizosphere Soil of Dominant Plants in Riparian Wetlands of Reservoir in Zhejiang Province, China

Soil bacterial play special roles in the maintenance and stabilization of wetland ecosystem. To investigate bacterial community structure and diversity in rhizosphere soils of four dominant plants in riparian wetlands of mountain reservoir in Zhejiang province, the V4+V5 areas of 16S rDNA gene of bacteria were sequenced and analyzed by the Illumina HiSeq 2500 high-throughput sequencing technology. The results indicated that 27 phylums, 70 classes, 144 orders, 218 families, and 370 genuses of bacteria were achieved, with Proteobacteria, Acidobacteria,Actinobacteria and Bacteroidetes being the dominant phylum and Gammaproteobacteria, Deltaproteobacteria, Acidobacteria, Actinobacteria, Betaproteobacteria and Thermoleophilia being the main class in the soils of riparian wetlands in this areas. The Shannon index and chao1 index of the rhizosphere soil bacteria of Salix babylonica were 8.64 and 585.58, respectively, which were the highest among the four plants, and that of Pterocarya stenoptera were the lowest, with 7.71 and 289.63, respectively. Soil pH, total nitrogen and organic matter were the main factors affecting the soil bacterial community structure in the soil rhizosphere of four dominant plants species in wetlands of riparian zone of reservoir in Zhejiang province.

Root-associated fungal microbiota of the perennial sweet sorghum cultivar under field growth.

Root-associated fungal microbiota, which inhabit the rhizosphere, rhizoplane and endosphere, have a profound impact on plant growth and development. Sorghum bicolor (L.) Moench, also called broomcorn or sweet sorghum, is a multipurpose crop. The comparison between annual and perennial sweet sorghum cultivars in terms of plant growth, as well as their interactions with belowground fungal microbiota, is still poorly understood, although there has been growing interest in the mutualism between annual sweet sorghum and soil bacteria or bacterial endophytes. In this study, the perennial sweet sorghum cultivar N778 (N778 simply) and its control lines TP213 and TP60 were designed to grow under natural field conditions. Bulk soil, rhizosphere soil and sorghum roots were collected at the blooming and maturity stages, and then the fungal microbiota of those samples were characterized by high-throughput sequencing of the fungal ITS1 amplicon. Our results revealed that the alpha diversity of the fungal microbiota in rhizosphere soil and root samples was significantly different between N778 and the two control lines TP213 and TP60 at the blooming or maturity stage. Moreover, beta diversity in rhizosphere soil of N778 was distinct from those of TP213 and TP60, while beta diversity in root samples of N778 was distinct from those of TP213 but not TP60 by PCoA based on Bray-Curtis and WUF distance metrics. Furthermore, linear discriminant analysis (LDA) and multiple group comparisons revealed that OTU4372, a completely unclassified taxon but with symbiotroph mode, was enriched in sorghum roots, especially in N778 aerial roots at the blooming stage. Our results indicate that Cladosporium and Alternaria, two fungal genera in the rhizosphere soil, may also be dominant indicators of sorghum yield and protein content in addition to Fusarium at the maturity stage and imply that the perennial sweet sorghum N778 can primarily recruit dominant psychrotolerant bacterial taxa but not dominant cold-tolerant fungal taxa into its rhizosphere to support its survival below the freezing point.

Effects of Rhizophagus intraradices on soybean yield and the composition of microbial communities in the rhizosphere soil of continuous cropping soybean

Soybean (Glycine max L.) is an important oil and economic crop in the world. However, soybean continuous cropping may lead to the decline of soybean yield and quality. The purpose of this study was to investigate the effects of Rhizophagus intraradices on soybean growth/yield, root rot disease index, and the composition of microbial communities in the rhizosphere soil of continuous cropping soybean at the R8 stage. The results showed that the 100-seed weight, seed-yield per plant, yield per 0.04 hectare, pods per plant, seed number per plant, branch number, plant height, and fresh weight of root and shoot, and disease index of soybean root rot were significantly affected by the inoculation of R. intraradices and soybean continuous cropping. The growth/yield indexes of soybean were the highest in the inoculated soybean plants under non-continuous cropping. Inoculation of R. intraradices and soybean continuous cropping significantly decreased and increased the disease index of soybean root rot, respectively. Bacterial diversity levels in the rhizosphere soil of continuous cropping soybean were lower than those in non-continuous cropping soybean. Furthermore, it also showed that inoculation of R. intraradices could increase the bacterial and fungal diversity in rhizosphere soil of soybean. It also showed that both inoculation and soybean continuous cropping had effects on the composition of microbial communities in the rhizosphere soil of soybean. Proteobacteria and Ascomycota were the most dominant bacterial and fungal phylum in all samples, respectively. The results would contribute to evaluating the biocontrol potential of R. intraradices against soybean root rot disease, increase soybean yield and improve the composition of microbial communities in the rhizosphere soil of continuous cropping soybean.

Genetic diversity and community composition of arbuscular mycorrhizal fungi associated with root and rhizosphere soil of the pioneer plant Pueraria phaseoloides

Genetic diversity and community composition of arbuscular mycorrhizal fungi associated with root and rhizosphere soil of the pioneer plant <i>Pueraria phaseoloides</i>

Soil nutrient dynamics relate to Epichloë endophyte mutualism and nitrogen turnover in a low nitrogen environment

Colonization by foliar fungal endophytes can assist host plants in the acquisition of soil nutrients, however understanding of the effects of Epichloë endophytes on soil nutrient dynamics and their consequences for nitrogen cycling remains fragmentary. Here, we studied the microbial functional genes involved in the soil nitrogen cycle and soil nutrient dynamics along a nitrogen gradient in rhizosphere soil of ryegrass infected by the endophyte Epichloë festucae var. lolii. High-throughput sequencing was used to determine the community of microbial functional genes. Plant nutrients and soil N2O flux were measured. The endophyte presence reduced the plant nutrient traits (shoot organic carbon, total nitrogen and total phosphorus, and root total phosphorus) under low nitrogen, while it increased the soil nutrient accumulation and altered the microbial environment. Plants with fungal endophyte showed higher community diversity in the AOB-amoA gene (ammonia-oxidation bacteria), had lower absolute and relative abundances in the nirK gene (nitrite reduction bacteria), and improved relative abundances and community diversity of the nosZ (nitrous oxide reduction bacteria). The nifH gene (N2 fixing bacteria) showed higher absolute and relative abundances, and diversity in rhizosphere soil of endophyte-infected plants. Changes in plant and soil traits mediated by endophyte infection were closely related to N2O fluxes and nifH gene abundance. The changes in CO2 flux by changing in soil microbial biomass nitrogen mediated by shoot biomass (induced by endophyte infection), which further altered the soil pH and NO3− content and lead to an increased in NH4+ accumulation. The current study demonstrated that the possible mechanism for endophyte-mediated nutrient uptake might promote the NH4+ accumulation through nitrogen mineralization and NO3− isomerization rather than enhancing in the nitrogen fixation process and inhibiting the denitrification process in N limited samples. By underlining the importance of endophyte infection for nutrient accumulation in plant and soil and biomass, these findings suggested that nutrient availability could initiate endophyte infection effects to mitigate the damage of low N stress for the host.

Effects of Continuous Cropping on Bacterial Community and Diversity in Rhizosphere Soil of Industrial Hemp: A Five-Year Experiment

Long-term continuous monoculture cultivation harms soil physicochemical and microbial communities in agricultural practices. However, little has been reported on the effect of continuous cropping of industrial hemp on bacterial community and diversity in the rhizosphere soil. Our study investigated the changes in physicochemical properties and bacterial communities of industrial hemp rhizosphere soils in different continuous cropping years. The results showed that continuous cropping would reduce soil pH and available phosphorus (AP), while electrical conductivity (EC), available nitrogen (AN), and available potassium (AK) would increase. Soil bacterial diversity and richness index decreased with continuous cropping years. At the same time, continuous cropping marked Acidobacteria, Bacteroidetes, and Gemmatimonadetes increase, and the Proteobacteria and Actinobacteria decreased. Moreover, we found that pH, AK, and AP were the critical factors associated with the changes in the abundance and structure of the bacterial community. Overall, our study first reported the effect of continuous cropping on the rhizosphere soil microflora of industrial hemp. The results can provide a theoretical basis for revealing the obstacle mechanism of continuous cropping of industrial hemp and contribute to the sustainable cultivation of industrial hemp in the future.

Nanoselenium integrates soil-pepper plant homeostasis by recruiting rhizosphere-beneficial microbiomes and allocating signaling molecule levels under Cd stress

Most studies have focused on regulation in a metabolic pathway in response to exogenous selenium under cadmium stress, rather than the change of key factors in soil and pepper plants. In this study, the correlations in environmental variables, microorganisms, metabolic pathways, Se and Cd morphology under nano-Se intervention were examined using metabolomics and microbial diversity in rhizosphere soil and pepper plants. The principal forms of Se in the soils were Se (VI) and SeCys, while SeMet and MeSeCys were the main components in the root, stem, leaves, and fruits in the treatment of nano-Se (5 and 20 mg/L) relative to the control. Soil enzymes,metabolites (fluorescein diacetate, urease, brassinolide, and p-hydroxybenzonic acid), and plant metabolites (rutin, luteolin, brassinolide, and abscisic acid) were remarkably enhanced by nano-Se fortification. The bio-enhancement of nano-Se can boost the beneficial microorganisms of Gammaproteobacteria, Alphaproteobacteria, Bacteroidia, Gemmatimonadetes, Deltaproteobacteria, and Anaerolineae in rhizosphere soil. Changes in microbial community were found to be strongly linked to the environment index, enzymes, soil metabolites, Se forms, which reduced Cd bioavailability and Cd accumulation in pepper plants. In conclusion, the nano-Se application integrates soil-plant balance by improving soil qualities and assigning signaling molecule levels in rhizosphere soil and pepper plants.

Succession Pattern in Soil Micro-Ecology Under Tobacco (Nicotiana tabacum L.) Continuous Cropping Circumstances in Yunnan Province of Southwest China.

Continuous cropping obstacle (CCO) is a common phenomenon in agricultural production and extremely threatens the sustainable development of agriculture. To clarify the potential keystone factors causing tobacco (Nicotiana tabacum L.) CCO, tobacco plants, topsoil, and rhizosphere soil were sampled from the fields with no, slight, and severe tobacco disease in Dali and Yuxi of Yunnan province in China. The physicochemical properties of topsoil and rhizosphere soil, the phenolic acids (PAs) contents in rhizosphere soil, and elemental contents in topsoil, rhizosphere soil, and tobacco plants were analyzed. Microbial diversity in rhizosphere soil was determined by the metagenomic sequencing method. The results showed that soil pH, texture, cation exchange capacity, organic matter, TC, TN, and available K contents showed a significant difference (p < 0.05) in soil physicochemical properties. There was a deficiency of B, K, Mg, and Mn contents in soil and/or tobacco plants. The contents of PAs, especially syringic acid in rhizosphere soil, varied significantly among the three sampling groups (p < 0.05). Meanwhile, microbial communities and functional genes changed from beneficial to harmful, showing an intimate correlation with soil pH and syringic acid content. It can be concluded that tobacco CCO could be allocated to the imbalance of soil micro-ecology, which possessed a regional feature at the two sampling sites.

Fungal community diversity and driving factors in rhizosphere soil of Caragana species across semi-arid regions

To investigate fungal community diversity in rhizosphere soil of Caragana species, and their relationships with ecological factors in the semi-arid regions of China, we collected soil samples from Caragana liouana and C. microphylla in different habitats. By using Illumina MiSeq high-throughput sequencing technology, we analyzed fungal diversity, community composition, and the driving factors. Results showed that 7 phyla, 20 classes, 43 orders, 66 families, and 78 genera were recorded from the rhizosphere soil. The dominant phyla in all sample sites were Ascomycota (37.7%), Basidiomycota (13.7%), and Zygomycota (4.3%). At the genus level, Penicillium, Geomyces, and Mortierella were dominant, and Rhizophagus and Glomus were also found in rhizosphere soil. The fungal Chao1 index, ACE index, and Simpson index of C. microphylla were significantly higher than those of C. liouana. There was significant difference between the two species in the composition of fungal communities. Results of redundancy analysis showed that soil organic carbon, total nitrogen, electrical conductivity, available potassium, altitude, total phosphorus and aridity index exhibited significant impacts on soil fungal diversity. Overall, those results enhanced our understanding of the relationships between rhizospheric microbial community diversity of Caragana species and ecological factors, and provided important information on the adaptive mechanisms of desert plants in semi-arid regions.

Impact of biocontrol microbes on soil microbial diversity in ginger (Zingiber officinale Roscoe).

Bacteria are the most diverse and abundant group of soil organisms that influence plant growth and health. Bacillus and Trichoderma are commonly used as biological control agents (BCA) that directly or indirectly act on soil bacteria. Therefore, it is essential to understand how the applied microbes impact the indigenous microbial community before exploring their activity in the control of soilborne diseases. MiSeq sequencing of the 16S rRNA gene was used to decipher the shift of rhizosphere bacterial community in ginger (Zingiber officinale Roscoe) treated with Bacillus subtilus and Trichoderma harzianum at different concentrations. The dominant phyla in treated and nontreated samples were Proteobacteria, Actinobacteria, Acidobacteria and comprised up to 54.7% of the total sequences. There were significant differences between BCA treated and nontreated samples in the bacteria community. BCA treated plants presented higher bacterial diversity than nontreated and higher dosage of BCA had a larger impact on rhizosphere microbiota, but the 'dose-response relationship' varied in different bacterial groups. Potential biomarkers at genus level were found, such as RB41, Pseudomonas, Nitrospira, Candidatus_Udaeobacter. The combined use of Bacillus subtilus and Trichoderma harzianum could alter bacterial community structure and diversity in rhizosphere soil. BCA-microbes interactions as well as soil microbial ecology should be noticed in plant disease management. © 2021 Society of Chemical Industry.