Rhizosphere Of Plants Research Articles

Micro PIXE mapping proves a differential distribution and concentration of trace elements in fungal structures of Rhizophagus intraradices

Arbuscular mycorrhizal (AM) fungi can sequester different potentially toxic elements, such as trace elements (TEs), within their structures to alleviate the toxicity for its host plant and themselves. To elucidate the role of AM fungi in TEs immobilization in the rhizosphere of host plants, it is important to know the TEs distribution in AM fungal structures. In the present study, we investigated the distribution and concentration of TEs within extraradical spores and mycelium of the AM fungus Rhizophagus intraradices, collected from the rhizosphere of Senecio bonariensis plants grown in a soil polluted with multiple TEs, by using Particle-Induced X-ray Emission with a micro-focused beam (micro PIXE). This technique enabled the simultaneous micrometric mapping of elements in a sample. The calculated values were compared with those in the polluted substrate, measured by the Wavelength Dispersive X-ray Fluorescence technique. The highest concentrations of Fe, P, Ti, Mn, Cr, Cu and Zn were found in AM fungal spores, where they were accumulated, while extraradical mycelium was enriched in Cu. Finally, we demonstrated that AM fungi can simultaneously accumulate high amounts of different TEs in their structures, thus reducing the toxicity of these elements to its host plant.

Radiation-Tolerant Fibrivirga spp. from Rhizosphere Soil: Genome Insights and Potential in Agriculture.

The rhizosphere of plants contains a wide range of microorganisms that can be cultivated and used for the benefit of agricultural practices. From garden soil near the rhizosphere region, Strain ES10-3-2-2 was isolated, and the cells were Gram-negative, aerobic, non-spore-forming rods that were 0.3-0.8 µm in diameter and 1.5-2.5 µm in length. The neighbor-joining method on 16S rDNA similarity revealed that the strain exhibited the highest sequence similarities with "Fibrivirga algicola JA-25" (99.2%) and Fibrella forsythia HMF5405T (97.3%). To further explore its biotechnological potentialities, we sequenced the complete genome of this strain employing the PacBio RSII sequencing platform. The genome of Strain ES10-3-2-2 comprises a 6,408,035 bp circular chromosome with a 52.8% GC content, including 5038 protein-coding genes and 52 RNA genes. The sequencing also identified three plasmids measuring 212,574 bp, 175,683 bp, and 81,564 bp. Intriguingly, annotations derived from the NCBI-PGAP, eggnog, and KEGG databases indicated the presence of genes affiliated with radiation-resistance pathway genes and plant-growth promotor key/biofertilization-related genes regarding Fe acquisition, K and P assimilation, CO2 fixation, and Fe solubilization, with essential roles in agroecosystems, as well as genes related to siderophore regulation. Additionally, T1SS, T6SS, and T9SS secretion systems are present in this species, like plant-associated bacteria. The inoculation of Strain ES10-3-2-2 to Arabidopsis significantly increases the fresh shoot and root biomass, thereby maintaining the plant quality compared to uninoculated controls. This work represents a link between radiation tolerance and the plant-growth mechanism of Strain ES10-3-2-2 based on in vitro experiments and bioinformatic approaches. Overall, the radiation-tolerant bacteria might enable the development of microbiological preparations that are extremely effective at increasing plant biomass and soil fertility, both of which are crucial for sustainable agriculture.

Sedimentary organic matter load influences the ecological effects of submerged macrophyte restoration through rhizosphere metabolites and microbial communities

Organic matter (OM) accumulation in lake sediments has doubled owing to human activities over the past 100 years, which has negatively affected the restoration of submerged vegetation and ecological security. Changes in the pollution structure of sediments caused by plant recovery and rhizosphere chemical processes under different sediment OM levels are the theoretical basis for the rational application of plant rehabilitation technology in lake management. This study explored how Vallisneria natans mediates changes in sediment N and P through rhizospheric metabolites and microbial community and function under low (4.94 %) and high (17.35 %) sediment OM levels. V. natans promoted the accumulation of NH4-N in the high-OM sediment and the transformation of Fe/Al-P to Ca-P in the low-OM sediment. By analyzing 63 rhizospheric metabolites and the sediment microbial metagenome, the metabolites lactic acid and 3-hydroxybutyric acid and the genus Anammoximicrobium were found to mediate NH4-N accumulation in the high-OM sediment. Additionally, 3-hydroxy-decanoic acid, adipic acid, and the genus Bdellovibrionaceae mediated the transformation of Fe/Al-P to Ca-P in the low-OM sediment. The growth of V. natans enriched the abundance of functional genes mediating each step from nitrate to ammonia and the genes encoding urease in the high-OM sediment, and it up-regulated three genes related to microbial phosphorus uptake in the low-OM sediment. This study revealed the necessity of controlling endogenous pollution by recovering submerged macrophytes under high- and low-OM conditions from the perspective of the transformation of inorganic nitrogen and phosphorus.

Amaranth Plants with Various Color Phenotypes Recruit Different Soil Microorganisms in the Rhizosphere.

To explore and utilize the abundant soil microorganisms and their beneficial functions, high-throughput sequencing technology was used to analyze soil microbial compositions in the rhizosphere of red and green amaranth varieties. The results showed that significant differences in soil microbial composition could be found in the rhizosphere of amaranth plants with different color phenotypes. Firstly, soil bacterial compositions in the rhizosphere were significantly different between red and green amaranths. Among them, Streptomyces, Pseudonocardia, Pseudolabrys, Acidibacter, norank_ f_ Micropepsaceae, Bradyrhizobium, and Nocardioides were the unique dominant soil bacterial genera in the rhizosphere of red amaranth. In contrast, Conexibacter, norank_f_norank_o_norank_c_TK10, and norank_f_ norank_o_ norank_ c_AD3 were the special dominant soil bacterial genera in the rhizosphere of green amaranth. Additionally, even though the soil fungal compositions in the rhizosphere were not significantly different between red and green amaranths, the abundance of the dominant soil fungal genera in the rhizosphere showed significant differences between red and green amaranths. For example, unclassified_k__Fungi, Fusarium, Cladophialophora, unclassified_c__Sordariomycetes and unclassified_p__Chytridiomycota significantly enriched as the dominant soil fungal genera in the rhizosphere of the red amaranth. In contrast, Aspergillues only significantly enriched as the dominant soil fungal genus in the rhizosphere of green amaranth. All of the above results indicated that amaranth with various color phenotypes exactly recruited different microorganisms in rhizosphere, and the enrichments of soil microorganisms in the rhizosphere could be speculated in contributing to amaranth color formations.

Persistence and Microbiome Modification in Rhizoctonia solani-Inoculated Rhizosphere Following Amendment with a Bacillus Biocontrol Agent

Bacterial biocontrol agents that antagonize soilborne pathogens are increasingly considered alternatives to chemical pesticides, but their in vivo efficacy is often inconsistent, restricting commercial use. The efficacy of a biocontrol agent can depend on rhizosphere competence and its interaction with native microbiomes, which can affect ecosystem functioning. This study investigated the capacity of a Bacillus cereus sensu lato biocontrol strain (S-25) to persist on roots and in the rhizosphere of cucumber and evaluated its impact on bacterial and fungal community composition in the rhizosphere in the absence and presence of Rhizoctonia solani, the causative agent of damping-off disease in young seedlings. Following amendment, S-25 abundance in the cucumber rhizosphere decreased by two orders of magnitude but remained relatively high for the duration of the experiment, in contrast to the root surface, where it was not detected. Amendment with S-25 significantly reduced the incidence of disease caused by R. solani without reducing the relative abundance of the fungal pathogen. Interestingly, R. solani did not substantially alter the rhizosphere microbial community, whereas S-25 reduced bacterial diversity and facilitated a shift in community composition, with increased relative abundance of Acidobacteriota and Actinomycetota, and reduced abundance of Pseudomonadota, Bacteroidota, and Verrucomicrobiota. Collectively, this study provides important insights into the mode of persistence of biocontrol agents and their effect on native microbiomes in the rhizosphere of pathogen-inoculated plants. It demonstrates that amendment can significantly alter local microbiomes and suggests that optimizing amendment regimes or selecting strains with higher rhizosphere competence can enhance future biocontrol agents.

Chitooligosaccharides and Arbuscular Mycorrhizal fungi alleviate the damage by Phytophthora nicotianae to tobacco seedlings by inducing changes in rhizosphere microecology

Arbuscular mycorrhizal fungi (AMF) and Chitooligosaccharide (COS) can increase the resistance of plants to disease. COS can also promote the symbiosis between AMF and plants. However, the effects of AMF & COS combined application on the rhizosphere soil microbial community of tobacco and the improvement of tobacco's resistance to black shank disease are poorly understood.·We treated tobacco with AMF, COS, and combined application of AMF & COS (AC), respectively. Then studied the incidence, physio-biochemical changes, root exudates, and soil microbial diversity of tobacco seedling that was inoculated with Phytophthora nicotianae. The antioxidant enzyme activity and root vigor of tobacco showed a regular of AC > AMF > COS > CK, while the severity of tobacco disease showed the opposite regular. AMF and COS enhance the resistance to black shank disease by enhancing root vigor, and antioxidant capacity, and inducing changes in the rhizosphere microecology of tobacco. We have identified key root exudates and critical soil microorganisms that can inhibit the growth of P. nicotianae. The presence of caprylic acid in root exudates and Bacillus (WdhR-2) in rhizosphere soil microorganisms is the key factor that inhibits P. nicotianae growth. AC can significantly increase the content of caprylic acid in tobacco root exudates compared to AMF and COS. Both AMF and COS can significantly increase the abundance of Bacillus in tobacco rhizosphere soil, but the abundance of Bacillus in AC is significantly higher than that in AMF and COS. This indicates that the combined application of AMF and COS is more effective than their individual use. These findings suggest that exogenous stimuli can induce changes in plant root exudates, regulate plant rhizosphere microbial community, and then inhibit the growth of pathogens, thereby improving plant resistance to diseases.

Photosynthetic activity and growth of poblano pepper biofertilized with plant growth promoting rhizobacteria and arbuscular mycorrhizal fungi

The rhizosphere of plants are natural hosts for beneficial microorganisms such as plant growth-promoting rhizobacteria (PGPR) and arbuscular mycorrhizal fungi (AMF). The objective of this work was to determine the effect of a consortium of AMF and three strains of PGPR on growth, gas exchange and phosphorus content in poblano pepper plants. An experiment was established in a completely randomized design with factorial arrangement, with two factors: AMF [Funneliformis geosporum and Claroideoglomus sp. (AM) and without AM (WM)] and PGPR [Rhizobium nepotum (B1), Serratia plymuthica (B2), Pseudomonas tolaasii (B3) and without PGPR (WB)]; generating eight treatments: T1) AM+B1, T2) AM+B2, T3) AM+B3, T4) AM+WB, T5) WM+B1, T6) WM+B2, T7) WM+B3 and T8) WM+WB. Plant height, number of leaves, leaf area, number of flowers, dry biomass, phosphorus content and AMF colonization were measured; internal CO2 concentration (Ci), transpiration rate (E), stomatal conductance (gS) and photosynthesis rate (Pn) were determined in leaves. Co-inoculation with AM+B3 promoted greater height (35%), number of leaves (66%), leaf area (62%), dry biomass (140%), phosphorus content (195%) and mycorrhizal colonization (26%); AM+B2 improved Ci (5%), E (8%), gS (5%) and Pn (9%) in poblano pepper leaves, compared to the control treatment (WM+WB). Biofertilization with AMF and PGPR improved gas exchange and growth of poblano pepper.

Specification of Rhizospheric Characteristics of Some Bacteria Identified by MALDI TOF MS from Agricultural Soils in Kirsehir Province (Akçakent and Çiçekdağı) Districts

The rhizosphere are site of plant-microorganism interaction, and have critical impotance in events like nutrient supply, the production of compounds that support plant growth and phytopathogen protection. This study reports 52 bacteria isolated from 5 different plant rhizospheres (Hordeum vulgare, Avena sativa, Cicer arietinum, Helianthus annuus, and Phaseolus vulgaris) of two agricultural districts of Kırşehir (Akçakent and Çicekdağı regions) in Türkiye. Morphological, biochemical, plant growth-promoting characteristics (including production of indole-3-acetic acid, siderophore, nitrogen fixation, and phosphate solubilization) using MALDI-TOF-MS techniques were used to identify the isolates. Among all isolates, 33 isolate were Gram positive and 19 were Gram negative. Furthermore 40% of them were classified as Bacillus species, 10% belonged to Pseudomonas species, 7% were Acinetobacter species, 4% were Pantoeae species, and 39% other species (Blastomonas, Lysinibacillus, Comamonas, Alcaligenes, Bifidobacterium, Aromatoleum). It was seen that 12 isolates fixed nitrogen, 8 isolates produced dissolved inorganic phosphate, 12 isolates produced siderophores, 9 isolates were produced by IAA, and 14 isolates produced HCN during the screening of plant growth promoting properties. It is concluded that the culture of bacteria living in the rhizosphere are essential to promote soil fertility and sustainable agriculture. Therefore, there is a need to identify and use these strains with plant growth promoting properties in agriculture.

A potential CO2 carrier to improve the utilization of HCO3– by plant-soil ecosystem for carbon sink enhancement

IntroductionImproving the rhizospheric HCO3– utilization of plant-soil ecosystem could increase the carbon sink effect of terrestrial ecosystem. However, to avoid its physiological stress on the crop growth, the dosage of HCO3– allowed to add into the rhizosphere soil was always low (i.e., <5–20 mol/m3). ObjectivesTo facilitate the utilization of relatively high concentrations of HCO3– by plants in the pursuit of achieving terrestrial carbon sink enhancement. MethodsIn this study, the feasibility of directly supplementing a high concentration HCO3– carried by the biogas slurry to the plant rhizosphere was investigated using the tomato as a model plant. ResultsThe CO2-rich biogas slurry was verified as a potential CO2 carrier to increase the rhizospheric HCO3– concentration to 36 mol/m3 without causing a physiological stress. About 88.3 % of HCO3– carried by biogas slurry was successfully fixed by tomato-soil ecosystem, in which 43.8 % of HCO3– was assimilated by tomato roots for the metabolism, 0.5 ‰ of HCO3– was used by microorganisms for substances synthesis of cell structure through dark fixation, and 44.4 % of HCO3– was retained in the soil. The rest of HCO3– (∼11.7 %) might escape into the atmosphere through the reaction with H+. Correspondingly, the carbon fixation of tomato-soil ecosystem increased by 150.1 g-CO2/m2-soil during a tomato growth cycle. As for the global countries that would adopt the strategy proposed in this study to cultivate the tomato, an extra carbon sink of soil with about 1031.1 kt-C per year (i.e., an additional 0.21 tons of carbon per hectare soil) could be obtained. ConclusionThis would be consistent with the goal of soil carbon sink enhancement launched at COP21. Furthermore, the regions with low GDP per capita may easily achieve a high reduction potential of CO2 emissions from the agricultural land after adopting the irrigation of CO2-rich biogas slurry.

Development of a Rhizobium Seed Coating to Establish Lupine Species on Degraded Rangelands.

Restoring native plant species on degraded landscapes is challenging. Symbiotic partners in the plant rhizosphere can aid in nutrient acquisition, pathogen protection, stress tolerance, and many other processes. However, these microbes are often absent in altered landscapes and need to be re-integrated to improve restoration efforts. We evaluated, within a laboratory setting, the ability of commercial and indigenous rhizobia strains to form nodules on lupine species used for rangeland seedings in the Great Basin region of the Western United States and ascertained if these strains could be applied through a seed coating. We also evaluated if a compost amendment applied via seed coating could further enhance the performance of the rhizobia strains. Our analysis showed that successful nodulation could occur using commercial and wildland-collected indigenous strains through either a liquid culture applied to seedlings or as a dry seed coating. However, the number of root nodules and the presence of a pink color (indicating nitrogen fixation) were typically higher in the commercial product than in the indigenous strains. Compost did not improve nodulation or the performance of the nodules; however, this treatment alone improved shoot growth. Overall, these results suggest that commercial rhizobium may be more effective in improving plant growth, and future research with native rhizobia may want to consider identifying strains compatible with seed-coating delivery. Longer-term studies are now merited for assessing how the rhizobia strains evaluated in this study influence plant growth, particularly in a field setting.

A Synergistic Indole-3-Acetic Acid-Producing Synthetic Bacterial Consortium Benefits Walnut Seedling Growth

Synthetic microbial communities (SynComs) have been shown to be an ecofriendly alternative for promoting plant growth. However, the mechanisms by which SynCom inoculants drive plant growth promotion in rhizosphere soil are still not fully explored. Herein, we designed a three-strain consortium based on the biocompatibility among strains and indole-3-acetic acid (IAA) production. The consortium containing Bacillus safensis 5-49, Bacillus stratosphericus 5-54, and Bacillus halotolerans 6-30 possessed a synergistic effect on IAA production and biofilm formation. Genetic analysis suggested that IAA was synthesized through tryptophan-dependent pathways in the strains. The consortium outperformed the plant growth-promoting effect observed with single strains, showing an increase in walnut (Juglans regia) seedling dry weight by 92.3% over the non-inoculated plants after 60 days of cultivation. This effect was underpinned by the synergistic interactions of the consortium, which was evidenced by the significantly increased relative abundance of Bacillus and tryptophan metabolism-associated genes in the rhizosphere of consortium-inoculated plants. Meanwhile, the consortium increased the relative abundance of indigenous Pseudomonas in rhizosphere soil, providing a synergistic effect on improving soil enzyme activities and thus available nutrients. The available N, P, and K contents in the consortium-inoculated plant rhizosphere were 3.77–28.4% higher than those in non-inoculated samples. This work provided an efficient bacterial consortium and proposed the mode of action by which this consortium improved plant growth and soil fertility.

Community metagenomics reveals the processes of cadmium resistance regulated by microbial functions in soils with Oryza sativa root exudate input

Plants exert a profound influence on their rhizosphere microbiome through the secretion of root exudates, thereby imparting critical effects on their growth and overall health. The results unveil that japonica rice showcases a remarkable augmentation in its antioxidative stress mechanisms under Cd stress. This augmentation is characterized by the sequestration of heavy metal ions within the root system and the prodigious secretion of a spectrum of flavonoids, including Quercetin, Luteolin, Apigenin, Kaempferide, and Sakuranetin. These flavonoids operate as formidable guardians, shielding the plant from oxidative damage instigated by Cd-induced stress. Furthermore, the metagenomic analyses divulge the transformative potential of flavonoids, as they induce profound alterations in the composition and structural dynamics of plant rhizosphere microbial communities. These alterations manifest through the recruitment of plant growth-promoting bacteria, effectively engineering a conducive milieu for japonica rice. In addition, our symbiotic network analysis discerns that flavonoid compounds significantly improved the positive correlations among dominant species within the rhizosphere of japonica rice. This, in turn, bolsters the stability and intricacy of the microenvironmental ecological network. KEGG functional analyses reveal a notable upregulation in the expression of flavonoid functional genes, specifically cadA, cznA, nccC, and czrB, alongside an array of transporters, encompassing RND, ABC, MIT, and P-ATPase. These molecular orchestrations distinctly demarcated the rhizosphere microbiome of japonica rice, markedly enhancing its tolerance to Cd-induced stress. These findings not only shed light on the establishment of Cd-resistant bacterial consortia in rice but also herald a promising avenue for the precise modulation of plant rhizosphere microbiomes, thereby fortifying the safety and efficiency of crop production.

Genotypic and Phenotypic Characterization of Pseudomonas atacamensis EMP42 a PGPR Strain Obtained from the Rhizosphere of Echinocactus platyacanthus (Sweet Barrel).

Plant growth-promoting rhizobacteria (PGPR) are a group of bacteria that associate with the rhizosphere of plants; one of the most abundant bacterial genera in this ecological niche is Pseudomonas, which is constantly expanding due to the emergence of new species such as Pseudomonas atacamensis, whose discovery in 2019 has led to the characterization of several strains from different environments but taxonomically related. The objective of this work was to phenotypically and molecularly characterize P. atacamensis strain EMP42, isolated from the rhizosphere of Echinocactus platyacanthus. The strain EMP42 is able to use different substrates and reduce oxidative stress in plants. It is capable of improving growth parameters such as the number of inflorescences and the height of the aerial body of Arabidopsis thaliana, as well as the germination and seedling survival of the cacti Echinocactus platyacanthus and Astrophytum capricorne. The genetic structure of P. atacamensis EMP42 consists of a closed chromosome of 6.14 Mbp, and 61.1% GC content. It has 5572 genes, including those associated with PGPR activities, such as the trpABCDE, SAP, phoABPRU and acsABC genes, among others, and three ncRNA loci, nine regulatory regions, five complete rRNA operons and three CRISPR-Cas loci, showing phylogenomic similarities with the reference strain P. atacamensis B21-026. Therefore, this study contributes to the understanding of genomic diversity within P. atacamensis and, particularly, highlights the potential application of strain EMP42 as a PGPR.

Gongronella sp. w5 hydrolyzes plant sucrose and releases fructose to recruit phosphate-solubilizing bacteria to provide plants with phosphorus.

This work supported that after absorbing plant sucrose, Gongronella sp. w5 mainly releases sucrose hydrolysis product fructose into the environment. Fructose was used as a carbon source and signaling molecules to induce PSB to co-produce higher alkaline phosphatase activity, releasing soil-available phosphorus and promoting M. truncatula growth. This is the first report that plant-beneficial fungi could directly metabolize sucrose from plants and then recruit PSB to aid P acquisition by providing fructose. Our findings revealed the diversity in pathways of plant-fungi-PSB interactions on soil P acquisition and deepened our understanding of the cooperation of growth-promoting microorganisms in plant rhizosphere.

Effects of uranium mining on the rhizospheric bacterial communities of three local plants on the Qinghai-Tibet Plateau.

In this study, we used 16S high-throughput sequencing to investigate the effects of uranium mining on the rhizospheric bacterial communities and functions of three local plant species, namely, Artemisia frigida, Acorus tatarionwii Schott., and Salix oritrepha Schneid. The results showed that uranium mining significantly reduced the diversity of rhizospheric bacteria in the three local plant species, including the Shannon index and Simpson index (P < 0.05). Interestingly, we found that Sphingomonas and Pseudotrichobacter were enriched in the rhizosphere soil of the three local plants from uranium mining areas, indicating their important ecological role. The three plants were enriched in various dominant rhizospheric bacterial populations in the uranium mining area, including Vicinamidobacteriaceae, Nocardioides, and Gaiella, which may be related to the unique microecological environment of the plant rhizosphere. The rhizospheric bacterial community of A. tatarionwii plants from tailings and open-pit mines also showed a certain degree of differentiation, indicating that uranium mining is the main factor driving the differentiation of plant rhizosphere soil communities on the plateau. Functional prediction revealed that rhizospheric bacteria from different plants have developed different functions to cope with stress caused by uranium mining activities, including enhancing the translational antagonist Rof, the translation initiation factor 2B subunit, etc. This study explores for the first time the impact of plateau uranium mining activities on the rhizosphere microecology of local plants, promoting the establishment of effective soil microecological health monitoring indicators, and providing a reference for further soil pollution remediation in plateau uranium mining areas.

Rhizosphere hydraulic regulation in maize: tailoring rhizosphere properties to varying soil textures and moistures

Abstract Aims Motivated by recent studies highlighting the active role of plants in influencing the hydraulic properties of the rhizosphere through mucilage exudation, this study explored the effect of plant rhizosphere regulation on the emergent hydraulic properties of the rhizosphere under varying soil texture and moisture levels. Methods Maize (Zea mays) plants were cultivated in sand and loam soils exposed to varying moisture levels. Neutron radiography was employed to quantify the profile of water content ($${\theta }_{r})$$ θ r ) around lateral and crown roots. The $${\theta }_{r}$$ θ r were used to derive rhizosphere hydraulic indices such as rhizosphere extension ($${d}_{rh}$$ d rh ), water content at the root-soil interface ($${\theta }_{rs}$$ θ rs ), and water content in the rhizosphere ($${\theta }_{rh}$$ θ rh ). The latter two attributes were normalized by the respective bulk soil water contents ($${\theta }_{rs}^{*}$$ θ rs ∗ , $${\theta }_{rh}^{*}$$ θ rh ∗ ). Results Results showed a higher $${\theta }_{rs}^{*}$$ θ rs ∗ , $${\theta }_{rh}^{*}$$ θ rh ∗ and $${d}_{rh}$$ d rh in coarse-textured soil versus fine-textured soil. This indicates a more pronounced rhizosphere development in sand compared to loam, possibly via mucilage exudation to maintain better root-soil contact. In contrast, soil water content did not impact the rhizosphere properties of crown roots but impacted the rhizosphere properties of lateral roots. The derived rhizosphere water retention curves revealed a higher water-holding capacity of the rhizosphere in both soils compared to bulk soil. Conclusions Our study underscores that soil-grown maize plants dynamically adjust the hydraulic properties of their rhizosphere in response to external factors, primarily aiming to optimize root-soil contact. That leads to a more pronounced rhizosphere in coarser textures, interacting with the soil moisture.

Effect of Groundfix and Ecostern biological preparations on soil microbiota under soybean (Glycine max L.) cultivation

In recent years, the system of farming using biologisation elements has become increasingly popular as an effective tool in agricultural production. By introducing agronomically useful microbiota into the soil, whose living cells are part of biological products (including biodestructors and biofertilisers), many valuable processes are triggered: restorative changes in the soil ecosystem by expanding microbial cenosis, improving its phytosanitary condition, protecting future crops of crop rotation from the allopathic effects of predecessors, increasing the availability of nutrients in the soil and improving its structure, as well as increasing yields and improving the quality of agricultural products. The aim of the research was to determine the effect of biological products based on bacteria of the genera: Bacillus, Paenibacillus, Azotobacter, Enterobacter, Enterococcus, Agrobacterium and fungi of the genus Trichoderma on the main ecological and trophic groups of soil microorganisms during the cultivation of soybean plants. The study was conducted using laboratory and vegetation methods of research in the conditions of the Institute of Applied Biotechnology LLC. Soybean seeds of Kent variety (SAATBAULINZ, Austria) were treated with biological products produced by BTU: biofertiliser Groundfix® (Bacillus subtilis, B. megaterium var. phosphaticum, Azotobacter chroococcum, Enterobacter sp, cell titer 0.5–1.5·109 CFU/cm3), biodestructor Ecostern® Classic (Bacillus, Paenibacillus, Azotobacter, Enterobacter, Enterococcus, Agrobacterium and fungi of the genus Trichoderma — cell titer not less than 2.5– 5.0·109 CFU/cm3) according to the recommended doses. The effectiveness of biological products Groundfix and Ecostern Classic in the formation of ecological and trophic groups of soil rhizosphere microorganisms for the cultivation of soybean plants of Kent variety is highlighted. DSTU 7847:2015 was used to determine soil microorganisms and their associations. The coefficients of soil mineralisation, oligotrophicity and pedotrophicity were calculated by the ratio of the corresponding ecological and trophic groups. It was found that under the action of biological products Ecostern Classic and Groundfix in the rhizosphere of soybean plants, the number of ammonifiers increased by 1.8–2.1 times, oligonitrophilic bacteria (including bacteria of the genus Azotobacter) — by 14.3–33.3%, oligotrophs — by 54–57% compared to the control variant. The number of pedotrophs in soybean plants grown with the addition of Ecostern Classic biological product was 1.6·105 CFU/g soil, which is 1.5 times lower than in the control. The highest values of pedotrophs were determined for the soil in the variant with Kent soybean grown under the influence of the biological product Groundfix, which is 4% higher compared to the control. Under the influence of biological products Ecostern Classic and Groundfix, the number of microorganisms that use mineral forms of nitrogen decreased by 2.3–8 times, respectively, compared to the control. According to the values of the coefficients of oligotrophicity, nitrogen mineralisation and immobilisation, and pedotrophicity, the direction of soil biological processes was characterised. The coefficient of oligotrophicity in the studied soil samples under the influence of biological products was 0.28–0.35, which indicates a high supply of nutrients to the soil microbiome. Soil variants, when growing soybean plants in the presence of biological products, had a lower pedotro­phicity coefficient. Thus, when soybean plants were grown under the influence of the biological product Groundfix (0.54), the value of the pedotrophicity coefficient was 2 times lower compared to the control (1.09), while under the influence of Ecostern (0.4) it was 2.7 times lower compared to the control. This indicates the accumulation of stable organic compounds and humus formation. The soil under the influence of the studied biological products is characterized by a sufficient amount of available nitrogen, high supply of soil microbiome with nutrients, accumulation of stable organic compounds and stable humus formation. The use of biological products Groundfix and Ecostern Classic improves microbial biodiversity and soil microbiota activity during soybean cultivation, increases the number of specific microbial taxa involved in the suppression of phytopathogenic microorganisms in the soil, promotes nutrient cycling and soil structure formation.

Bacteria from the rhizosphere of a selenium hyperaccumulator plant can improve the selenium uptake of a non-hyperaccumulator plant

Bacteria from the rhizosphere of a selenium hyperaccumulator plant can improve the selenium uptake of a non-hyperaccumulator plant

FTIR Characterization of Bioactive Functional Groups Present in Crude Extract of Mycoherbicides Produced from Consortium Culture of Rhizosphere Fungal Isolates

ABSTRACT Consortium culture can be a relatively cheap and environment-friendly technology for producing secondary metabolites like pesticides (herbicides). This study produced some metabolites from a consortium culture of fungal isolates obtained from the rhizospheres of Panicum maximum, Ipomoea involucrata and Amaranthus viridis. The isolates from rhizospheres of the above-named plants were co-cultured using Czapek broth and were incubated in an incubator shaker for 28 days. The co-culture combinations were: Aspergillus welwitschiae and Trichoderma hamatum (consortium 1), Aspergillus welwitschiae and Aspergillus aculeatus (consortium 2), and Aspergillus aculeatus and Trichoderma hamatum (consortium 3). Crude extracts from each consortium were characterized using Fourier Transform Infrared Spectroscopy (FTIR). The FTIR results showed that consortium 1 had peak spectra range from 418.57 cm−1 (S–S stretch of aryl disulfides) to 3462.34 cm−1 (alcohol, aliphatic primary amine), consortium 2 had peak spectra range from 420.5 cm−1 (halo compound) to 3456.65 cm−1 (alcohol, aliphatic primary amine) and consortium 3 had peak spectra from 457.14 cm−1 (halo compound) to 3448.84 cm−1 (alcohol, aliphatic primary amine). Some of the compounds produced by the consortia were pesticidal in nature and are hence, considered a potential technology in developing organic pesticides.

Genotype of pioneer plant Miscanthus is not a key factor in the structure of rhizosphere bacterial community in heavy metal polluted sites

Miscanthus is a common pioneer plant with abundant genetic variation in abandoned mines in southern China. However, the extent to which genetic differentiation among species modulates rhizosphere bacterial communities remains unclear. Miscanthus samples were collected from 26 typical abandoned heavy-metal mines with different soil types in southern China, tested using 14 pairs of simple sequence repeats (SSR) primers, and classified into two genotypes based on Nei’s genetic distance. The structure and diversity of rhizosphere bacterial communities were examined using 16 S rRNA sequencing. The results showed that among the factors affecting the rhizosphere bacterial community structure of Miscanthus samples, the role of genotype was not significant, and geographical conditions were the most important factors, followed by pH and total organic carbon (TOC). The process of rhizospheric community assembly varied among different genotypes; however, the recruited species and their abundances were similar. Collectively, we provided an approach based on genetic differentiation to quantify the relative contribution of genotypes to the rhizosphere bacterial community, demonstrating that genotypes contribute less than soil conditions. Our findings provide new insights into the role of host genetics in the ecological processes of plant rhizosphere bacterial communities in abandoned mines and provide theoretical support for microbe-assisted phytoremediation.