Rhizobium Leguminosarum Research Articles

ECONOMIC AND ENERGY EFFICIENCY OF PEA INOCULATION WHEN GROWING CROP IN THE SYSTEM OF ORGANIC PRODUCTION

Objective. To analyse economic and energy efficiency of inoculants based on a new strain Rhizobium leguminosarum Г222 in the technology of growing field peas. Methods. The calculation of the indicators of the economic efficiency of the cultivation of field peas for various seed treatment variants was carried out using methods and commonly used methodological approaches, which are based on a comparison of the results of the application of a certain agricultural measure with the costs of its implementation. The following indicators were studied: profit, cost per unit, payback of additional costs, as well as the level of profitability of production. Modelling of technological costs in the conditions of production scales using typical pea growing technologies has been used. The main agrotechnical operations have been modelled according to resource cost standards and product costing algorithms with the inclusion of additional operations and costs associated with the use of studied inoculants. In order to calculate the main indicators of the energy efficiency of the applied means for treatment of the pea seeds, the costs of all types of used resources and the obtained products were converted into energy equivalents according to generally accepted methods. Results. The use of inoculants based on R. leguminosarum Г222 contributes to increase in all the main indicators of economic efficiency: cost per unit, profit based on 1 ha of sown area and the level of profitability increase with the corresponding level of payback of additional costs. This is due to the higher rates of yield growth (and, accordingly, cash receipts) in experimental variants compared to the rates of increase of costs per unit area associated with the use of inoculants. According to the results of the energy efficiency analysis, it has been shown that the inoculation of peas with a new strain provides a high level of energy efficiency in terms of the ratio of the energy content of the obtained products to the energy consumption for its production (energy efficiency coefficient). The results of the comparative analysis of the calculated indicators show that in the variants with bacterization, there is a significant lag in the rates of increase of anthropogenic energy consumption per 1 ha of sown area versus the increase in yield and energy content of the obtained products. Additional energy costs associated with the use of inoculants are 8.00–24.39 times paid back by the energy of the additional harvest. Conclusion. The results of the analysis suggest high economic and energy efficiency of the use of the new strain R. leguminosarum Г222. The variant in which the use of R. leguminosarum Г222 was combined with a polysaccharide-protein complex is the most efficient.

Structural, rheological properties and antioxidant activities analysis of the exopolysaccharide produced by Rhizobium leguminosarum bv. viciae VF39

Microbial exopolysaccharide is an eco-friendly and non-toxic biopolymeric materials widely used in various industrial fields such as pharmaceutical, food and cosmetics based on its structural, rheological and physiochemical properties. A microbial exopolysaccharide (VF39-EPS) was directly isolated from Rhizobium leguminosarum bv. viciae VF39. Structural analysis using FTIR and 2D NMR spectroscopy confirmed the complete chemical structures of VF39-EPS as 3-hydroxybutanoylglycan with octasaccharide repeating units containing two pyruvyl, two acetyl, and one 3-hydroxybutanoyl group. VF39-EPS exhibited thermal stability up to 275 °C and showed characteristic rheological behaviors of structural fluid with weak gel-like properties above 4 % the aqueous solution, suggesting VF39-EPS as a potential effective thickener or hydrogel scaffolder. Flow behavior tests validated broad stability at a wide range of both pHs from 2 to 12 and temperatures from 25 to 75 °C, and even in the presence of various salts. Furthermore, VF39-EPS showed excellent antioxidant effects of 78.5 and 62.4 % (n = 3, p < 0.001) in DPPH scavenging activity and hydroxyl radical scavenging activity, respectively. Therefore, those structural, rheological and antioxidant properties suggest that VF39-EPS could be one of the excellent biomaterial candidates for cosmetic, food and pharmaceutical industries based on its characteristic rheological behaviors in various condition and excellent antioxidant activity.

Increasing diversity among Lens species for improving biological nitrogen fixation in lentil

AbstractExotic germplasm is a key resource for reintroducing genetic variability into cultivars. We evaluated 36 accessions from cultivated lentil (Lens culinaris Medik.) and six related wild species inoculated with a commercial strain of Rhizobium leguminosarum bv. viciae under greenhouse conditions. The objective was to explore Lens species and/or accessions that can contribute higher biological nitrogen fixation ability to the lentil crop. A split plot design was used with either Rhizobium inoculation, added nitrogen (+N), or neither as the main plots, and accessions in subplots randomized in blocks. Two repeats of the experiment were evaluated at flowering for N fixation and nodulation characters, and two subsequent experiments, with a subset of 14 accessions, were evaluated at maturity for seed production, seed quality, and harvest index. Differences in phenotypic expression corresponded to specific accessions but not to any particular Lens species. CDC Greenstar had the highest N fixation among lentil cultivars and also had superior yield results compared to the added N treatment. When inoculated, wild accessions, including IG 72643 (Lens orientalis), displayed unique and multiple desirable characteristics compared to cultivars, including indeterminate nodulation, higher N translocation, stable yield compared to added N treatment, and exceptionally high protein concentration in seeds.

Bioinput Inoculation in Common Beans to Mitigate Stresses Caused by a Period of Drought

Drought conditions have made it difficult for farmers to ensure the productivity of their crops. The objective of this study was to evaluate the potential of bioinputs in stress mitigation after a drought event in common beans. Two experiments were set up in a greenhouse. Firstly, two types of soils (clayey and sandy loam) were used. After seedling emergence, treatments were set: no bacteria inoculation (NB) and inoculation with Herbaspirillum frisingense AP21. Then, a differentiation on the irrigation (15 days) was performed with no water restriction (NWR) and with water restriction (WWR). Transpiration, stomatal conductance, leaf dry matter and proline were measured. Secondly, in the clayey soil, the bacteria treatments were NB, Herbaspirillum frisingense AP21, Rhizobium leguminosarum T88 and co-inoculation (AP21 + T88). A differentiation on the irrigation (15 days) was performed: NWR and WWR. Then, Fv/Fm, photosynthetic rate, proline and sugars were assessed, and the harvest occurred 97 days after emergence. For sandy loam soil bioinputs, they did not have an effect on the parameters evaluated. For clayey soil, H. frisingense AP21 increased the transpiration rate and stomatal conductance and hence improved the leaf dry matter in comparison to NB. Under WWR, the isolated inoculations of AP21 and T88 increased grain dry matter, but the co-inoculation showed low grain production, similar to no bacteria inoculation.

Effects of Elevated Temperature on Pisum sativum Nodule Development: I-Detailed Characteristic of Unusual Apical Senescence.

Despite global warming, the influence of heat on symbiotic nodules is scarcely studied. In this study, the effects of heat stress on the functioning of nodules formed by Rhizobium leguminosarum bv. viciae strain 3841 on pea (Pisum sativum) line SGE were analyzed. The influence of elevated temperature was analyzed at histological, ultrastructural, and transcriptional levels. As a result, an unusual apical pattern of nodule senescence was revealed. After five days of exposure, a senescence zone with degraded symbiotic structures was formed in place of the distal nitrogen fixation zone. There was downregulation of various genes, including those associated with the assimilation of fixed nitrogen and leghemoglobin. After nine days, the complete destruction of the nodules was demonstrated. It was shown that nodule recovery was possible after exposure to elevated temperature for 3 days but not after 5 days (which coincides with heat wave duration). At the same time, the exposure of plants to optimal temperature during the night leveled the negative effects. Thus, the study of the effects of elevated temperature on symbiotic nodules using a well-studied pea genotype and Rhizobium strain led to the discovery of a novel positional response of the nodule to heat stress.

Effects of Elevated Temperature on Pisum sativum Nodule Development: II-Phytohormonal Responses.

High temperature is one of the most important factors limiting legume productivity. We have previously shown the induction of senescence in the apical part of nodules of the pea SGE line, formed by Rhizobium leguminosarum bv. viciae strain 3841, when they were exposed to elevated temperature (28 °C). In this study, we analyzed the potential involvement of abscisic acid (ABA), ethylene, and gibberellins in apical senescence in pea nodules under elevated temperature. Immunolocalization revealed an increase in ABA and 1-aminocyclopropane-1-carboxylic acid (ACC, the precursor of ethylene biosynthesis) levels in cells of the nitrogen fixation zone in heat-stressed nodules in 1 day of exposure compared to heat-unstressed nodules. Both ABA and ethylene appear to be involved in the earliest responses of nodules to heat stress. A decrease in the gibberellic acid (GA3) level in heat-stressed nodules was observed. Exogenous GA3 treatment induced a delay in the degradation of the nitrogen fixation zone in heat-stressed nodules. At the same time, a decrease in the expression level of many genes associated with nodule senescence, heat shock, and defense responses in pea nodules treated with GA3 at an elevated temperature was detected. Therefore, apical senescence in heat-stressed nodules is regulated by phytohormones in a manner similar to natural senescence. Gibberellins can be considered as negative regulators, while ABA and ethylene can be considered positive regulators.

INTEGRATION OF BIOAGENTS AND CHEMICAL FUNGICIDES AGAINST SCLEROTINIA SCLEROTIORUM CAUSING STEM ROT IN CHICKPEA

One of the most harmful infections to chickpea plants, Sclerotinia sclerotiorum, causes stem rot and causes financial losses all over the world. Beneath the soil's surface, as sclerotia, the pathogen can live for a very long time alongside the detritus. As a result, the condition is extremely difficult to manage, has nearly no known treatments, and only a few types have been shown to be somewhat successful against the infection. Thus, the primary goal of the research is to investigate the effects of a variety of treatments, including Rhizobium leguminosarum + Pseudomonas fluorescens combination, Trichoderma viride, Saaf (Carbendazim 12%+ Mancozeb 63% WP), Vitavax Power (Carboxin 37.5%+ Thiram 37.5%), Hexaconazole, and Rhizobium leguminosarum + Pseudomonas fluorescens, to investigate their impact on S. sclerotiorum suppression. While maintaining sustainability, bioagents improve the soil's properties and productivity. Fungicides have been found to be effective when bio-agents are not able to control a disease. Therefore, in this investigation, both methods of treatment were used. The results of an experiment conducted in both in vitro and in vivo conditions showed that chemical treatment with Saaf fungicide and seed treatment with T. viride were highly efficient against S. sclerotiorum.

Polymorphism of Core and Symbiotically Specialized Genes in the Polytypic Species of Nodule Bacteria

The polytypic species of nodule bacteria Rhizobium leguminosarum (includes biovars viciae and trifolii) and Neorhizobium galegae (biovars orientalis and officinalis) differ in the nucleotide polymorphism of housekeeping genes (hkg) and of symbiotically specialized genes (sym) that control the formation of N2-fixing nodules in leguminous plants. In R. leguminosarum, p-distance values for sym genes are higher than for hkg genes in strains from the same and from different biovars. In N. galegae, differences between biovars in sym genes are higher than in hkg genes while within biovars, polymorphism in sym genes is lower than in hkg genes. Coefficients of biovar differentiation for both groups of genes are higher in N. galegae than in R. leguminosarum, possibly reflecting the spatial isolation of N. galegae biovars. In these species of rhizobia, the phylogenetic congruence of sym and hkg genes is more pronounced in N. galegae than in R. leguminosarum. This difference indicates an active transfer of sym genes in R. leguminosarum populations possibly representing an important factor of the deep diversification for symbiotic traits in this rhizobia species.

Mineral and Carbon Metabolic Adjustments in Nodules of Symbiotically Grown Faba Bean (Vicia faba L.) Varieties in Response to Organic Phosphorus Supplementation.

Phosphorus (P) is a major limiting factor for legume and symbiotic nitrogen fixation (SNF). Although overall adaptations of legumes to P supplementation have been extensively studied in connection with inorganic P, little information is currently available regarding nodulation or SNF responses to organic P (Po) in hydroponics. We investigated the mineral and carbon metabolism of Po-induced nodules of two contrasting faba bean varieties grown hydroponically under inorganic P (Pi), viz., in P-deficient (2 µM KH2PO4, -Pi), sufficient-P (200 µM KH2PO4, +Pi), and phytic acid (200 µM, Po) conditions, and were inoculated with Rhizobium leguminosarum bv. viciae 3841 and grown for 30 days. The results consistently reveal similar growth and biomass partitioning patterns between +Pi and Po, with both varying substantially from -Pi. In comparison, +Pi and Po observed equivalent accumulations of overall elemental P concentrations, with both increasing by 114 and 119%, respectively, relative to -Pi. A principal component analysis on metabolites showed a clear separation of the -Pi treatment from the others, with +Pi and Po correlating closely together, highlighting the nonsignificant differences between them. Additionally, the δ15N abundance of shoots, roots, and nodules was not significantly different between treatments and varieties and exhibited negative δ15N signatures for all tissues. Our study provides a novel perspective on mineral and carbon metabolism and their regulation of the growth, functioning, and reprogramming of nodules upon phytate supply.

Ecotoxic effect of agriculture and environmental important bioinoculant effective microorganism (EM) derived metabolites on microbial agro active agents

AbstractEffective microorganism (EM) – a mixture of beneficial microbial formulation are extensively utilized worldwide in agriculture as plant growth promotor and biocontrol agent. Because of their wide spectrum usage, it is necessary to study the non‐target effect against the beneficial organisms used in crop production. Though, the wider applications of EM in agriculture and the environment have revealed, the environmental quality management of EM mainly metabolites‐ biochemical compounds derived from EM have yet to be studied. With this objective, the present study is undertaken to evaluate the compatibility of EM derived metabolites on the selected microbial biofertilizers, biocontrol agents including biopesticidal agents. Metabolites were extracted from the culture‐free broth of EM culture using various solvents and the extracted metabolites were characterized by the gas chromatography‐ mass spectroscopy (GC‐MS). The food poisoning technique was adapted for the screening of toxic effects. Toxic effect of the metabolites derived from the respective solvent was confirmed by measuring the growth of the respective microbial strain's vegetative growth and sporulation efficacy by dual plate assay, dual liquid assay, and spore germination microscopic slide assay. Active principles of the metabolites were readily extracted in all the solvents and the possible presence of bioactive metabolites were characterized by GC‐MS. There was no significant difference between the control and extract recorded. In the case of Rhizobium leguminosarum, the colony diameters of ethyl acetate and acetone extract were 1.6 and 1.8 cm, respectively, as in control (1.8 cm). Similar findings were also recorded for Azospirillum lipoferum, Phosphobacterium sp., and Pseudomonas flurescens. However, growth inhibition including spore germination was recorded in petroleum ether and acetone extract. Further study will be useful to exploit the principles of EM and EM derived metabolites in agriculture and environment without affecting non target beneficial organism.

Effectiveness of biostimulants on growth, yield, and seed nutrient content of faba bean (Vicia faba L.) grown on two contrasting soil types

Faba bean is the main source of protein and minerals for most of Ethiopia’s population. However, soil fertility challenges production, and good agricultural practices are needed to increase yield and nutritional value. Pot and field experiments were conducted to evaluate the effect of the sole and combined application of biostimulants on faba bean growth, yield, and seed nutrient content. Effects of sole and/or combined applications of plant growth-promoting rhizobacteria (PGPR) (Bacillus subtilis, Pseudomonas fluorescens, and Rhizobium leguminosarum) and moringa leaf extract (MLE) were pre-evaluated under greenhouse conditions. Subsequently, selected treatments from this pot experiment were further evaluated on a local and Moti faba bean variety under field conditions on Nitisol and Vertisol. The biostimulant treatments significantly improved faba bean growth under greenhouse conditions. However, they did not influence the crop’s growth, yield, and seed nutrient content under field conditions. Varieties significantly (p < 0.05) influenced yields and yield components obtained from Vertisol, as well as seed micronutrient contents from both soils. A local variety was found to have higher nutrient content. Meanwhile, grain yield had a positive correlation with seed iron (Fe) content and a negative correlation with seed selenium (Se) and phosphorus (P) contents. In addition, seed Se content strongly correlated with P content. From this study, it could be concluded that using biostimulants does not help in improving faba bean attributes under field conditions. However, further examination of a wider range of biostimulants under field conditions is required to uncover their realistic effectiveness for bean crop biofertilization.

Isolation and Diagnosis of the Root Nodule Bacteria Associated with Mung Bean Plant in Gypsiferous Soil and Testing the Promotional Criterion of Isolates

The root nodule bacteria are utilized in the production of natural biological fertilizers to achieve clean agriculture by reducing chemical fertilizers. In this study, 35 samples of the root nodules associated with mung bean plants were collected from various agricultural areas of Iraq, Salah Al-Din Governorate on 4\\7\\2022, ten samples isolated by growing them on yeast extract mannitol agar (YEMA) and the phenotypically pure isolates were diagnosed based on the culture, microscopic and biochemical characteristics., The phenotypic diagnosis results showed that The color of the colonies was between white, creamy and yellow, Spherical, convex and smooth, gram-negative, was able to move and pink and light pink on Congo red stain medium and 9 isolates it was fast growing as it gave yellow color on YEMA-BTB bromothymol blue medium except for one isolate it was slow growing as it gave blue color and all isolates unable to grow on Hofer alkaline medium except for one isolate, The efficient isolate was selected in the production of indole acetic acid, chelating compounds and phosphate solubilization,. The results showed that isolates (M3, M4, M5, M6, M7) have a high ability for iron chelation. It was found that the (M6) isolate gave the highest phosphate solubilization and indole production, which showed a phosphorus solubilization of 39.504 mg P.L-1 and an indole production rate of 21.5 μg.ml-1. This was followed by the isolate (M3), which showed a phosphorus solubilization of 23.723 mg P.L-1 and an indole production rate of 17.2 μ.g.ml-1. Molecular diagnosis was performed for five competent isolates in the production of Indole acetic acid, production of chelating compounds, and phosphate solubilization. The isolates were molecularly diagnosed by PCR, the 16SrRNA gene was amplified, then the sequence of nitrogenous bases was analyzed and when matching with the global strains included in the NCBI Genetic Bank website, The results of molecular diagnosis showed that two isolates belong to Rhizobium bacteria. the results showed that (M3) isolate is %99.50 similar to the Rhizobium leguminosarum isolate OTU21_I. and the results showed that (M6) isolate is 99.48% similar to the Bradyrhizobium japonicum strain A3 and 99.96% to the Bradyrhizobium japonicum, strain:NK5 and therefore the isolates is genetically close to Rhizobium leguminosarum strain AE15 and Bradyrhizobium japonicum strain AE14 bacteria and has been recorded in the Global genome bank under accession number OP975690 and version number OP975690.1 for Rhizobium leguminosarum and accession number OP975688 and version number OP975688.1 for Bradyrhizobium japonicum and this record is the first for this bacteria which associated with mung bean in gypsiferous soils in Iraq.

Occurrence of the Ability to Suppress the Growth of Related Strains in Rhizobia

Abstract—Screening of 1019 strains of rhizobia Rhizobium leguminosarum and Neorhizobium galegae from the “Symbiont” collection of symbiotic rhizospheric microorganisms of the Institute of Biochemistry and Genetics, Ufa Research Center, Russian Academy of Sciences, which have been isolated from root nodules of 20 leguminous species, for the ability to suppress the growth of related strains of rhizobia was carried out. Inhibition of the growth of competing bacteria by rhizobia was shown to be rather common. On average, when grown on rich media, ~10% of rhizobial strains released antibacterial substances into the medium. At the same time, when a live culture of rhizobia was applied to the lawn of bacteria, the percentage of suppression was higher. The percentage of strains synthesizing antibacterial substances correlated also, to some extent, with the level of genetic diversity of the population of legume microsymbionts. A weak signal of impaired protein synthesis was found in the study of the mechanism of action of metabolites of 20 strains of rhizobia R. leguminosarum bv. viciae from root nodules of Lathyrus palustris and Lathyrus vernus. In other cases, the nature of the antibacterial action of bacterial metabolites could not be determined using the DualRep2 system.

Effect of Rhizobium leguminosarum Inoculation and Mulching on Growth and Yield of Chinese Long Bean (Vigna unguiculata subsp. sesquipedalis)

An experiment was conducted to evaluate the influence of Rhizobium leguminosarum inoculation and mulching on the growth and yield of Chinese long bean (Vigna unguiculata subsp. sesquipedalis) in Palungtar, Nepal. A split-plot design was used for the experiment, which was replicated four times. Plastic, straw, and no-mulch conditions constituted the main plot factor, while seeds with or without Rhizobium inoculation constituted the sub-plot elements. Growth parameters and yield-related traits of Chinese long beans were recorded at 15-day intervals. Transparent plastic mulching resulted in earlier flowering (46 days), while seed inoculation with Rhizobium resulted in a higher mean number of nodules (106.92) than non-inoculated treatments, with transparent plastic mulching resulting in the highest mean number of nodules (108.21). At 60 days after showing (DAS), plant height was greater in the inoculated treatment (69.23 cm), while at 30 DAS, the non-inoculated treatment had a higher number of leaves (22.28 cm). Similarly, pod length (49.98 cm), pod yield per plant (348.01 g), and total yield per hectare (16.07 t/ha) were all significantly higher with both plastic mulch and seed inoculation with Rhizobium than with the other treatments alone. A positive correlation was observed between plant height (0.81), number of branches (0.44), number of leaves (0.81), number of nodules per plant (0.6), and pod yield. This supports the potential benefits of using seed inoculation with Rhizobium in combination with mulching to improve Chinese long bean growth and increase yield as demonstrated by the results of this study.

Detection of Rhizobium leguminosarum bv. trifolii and Rhizobium leguminosarum bv. phaseoli isolated from root nodules of leguminous plants by multiplex-PCR

The genetic diversity of 4 R. leguminosarum bv. trifolii and R. leguminosarum bv. Phaseoli that was extracted from root nodes of Trifolium spp and Phaseolus vulgaris L cultivars circulated in Mosul soils were investigated. The bacteria strains under study show similar tolerance levels against some external factors. In the current study, using classical diagnosis methods, similarity and distance indices and DNA polymorphism were examined with the randomly amplified polymorphic DNA. The isolates were distributed through genetic diversification into two main classes, including two main branches, Rl2 and the other sub-group was divided into Rl3, and the neighboring group involved Rl1 and Rl4. It is noted that individual plants and abiotic aspects were less affected than the Genetic factor on bacterial diversity. On the other hand, in multiplex-PCR reaction, Our outcomes revealed specific amplified for R. leguminosarum bv. trifolii with amplification products 419 bp and R. leguminosarum bv. Phaseoli with amplification products 362 bp. Keywords: R. leguminosarum bv. phaseoli, R. leguminosarum bv. trifolii , nodules, multiplex-PCR, RAPD-PCR .

Evaluation Effect of Inoculum Prepared from Local Bacterial Isolates of Rhizobium and Nitrogen Fertilization on some Growth Traits of Mung Bean Plant in Gypsiferous Soil

The root nodule bacteria are utilized in the production of natural biological fertilizers to achieve clean agriculture by reducing chemical fertilizers. Therefore, the bacterial inoculum was prepared from local isolates of Rhizobium leguminosarum and Bradyrhizobium japonicum, which were morphologically and molecularly characterized. Subsequently, the efficacy of the prepared inoculum was tested in the formation of root nodules and some growth traits of mung bean plants in gypsiferous soil at three levels of nitrogen fertilization (0, 40, 80) kg N ha-1 The results showed a significant increase in all plant growth traits during the flowering stage for the treatments inoculated with Rhizobium leguminosarum and Bradyrhizobium japonicum bacteria in comparison to the treatment without inoculation. The inoculated treatments outperformed the non-inoculated treatment significantly. Additionally, the treatment inoculated with Bradyrhizobium japonicum showed a significant superiority over the treatment inoculated with Rhizobium leguminosarum in all studied growth traits, the recorded values for the count of root nodules were (0.00, 8.33, 35.11) nodule. plant-1, The wet mass of nodules was (0.00, 0.091, 1.802) g. plant-1, and dry mass of nodules was (0.00, 0.010, 0.337) g. plant-1. The plant height was (52.11, 56.22, 58.05) cm. plant-1. The dry mass of the vegetative part, was (14.03, 20.10, 23.05) g. plant-1, and, the dry mass of the root part was (1.37, 2.57, 2.67) g. plant-1. The nitrogen content was (1.547, 2.765, 3.028) % phosphorus (0.121, 0.236, 0.377) %, and potassium (1.168, 2.342, 3.562) % in the vegetative part. The absorbed nitrogen in the vegetative part was (217.41, 541.10,718.02) mg. plant-1. These values were recorded for the non-inoculated treatment, Rhizobium leguminosarum inoculated treatment, and Bradyrhizobium japonicum inoculated treatment, respectively. The results showed a significant superiority for the 40 kg N ha-1 fertilized treatment in comparison to both the unfertilized treatment and the 80 kg N/ha-1 fertilized treatment in all studied traits. The interaction effect was significant, as the treatment that was inoculated with Bradyrhizobium japonicum and 40 kg N ha-1 fertilized treatment exhibited significant superiority over the other treatments in all studied traits.

Characterization and Genomic Analysis of Fererhizobium litorale gen. nov., sp. nov., Isolated from the Sandy Sediments of the Sea of Japan Seashore.

The taxonomic status of two gram-negative, whitish-pigmented motile bacteria KMM 9576T and KMM 9553 isolated from a sandy sediment sample from the Sea of Japan seashore was defined. Phylogenetic analysis revealed that strains KMM 9576T and KMM 9553 represent a distinct lineage within the family Rhizobiaceae, sharing 100% 16S rRNA sequence similarity and 99.5% average nucleotide identity (ANI) to each other. The strains showed the highest 16S rRNA sequence similarities of 97.4% to Sinorhizobium garamanticum LMG 24692T, 96.9% to Ensifer adhaerens NBRC 100388T, and 96.8% to Pararhizobium giardinii NBRC 107135T. The ANI values between strain KMM 9576T and Ensifer adhaerens NBRC 100388T, Sinorhizobium fredii USDA 205T, Pararhizobium giardinii NBRC 107135T, and Rhizobium leguminosarum NBRC 14778T were 79.9%, 79.6%, 79.4%, and 79.2%, respectively. The highest core-proteome average amino acid identity (cpAAI) values of 82.1% and 83.1% were estimated between strain KMM 9576T and Rhizobium leguminosarum NBRC 14778T and 'Rhizobium album' NS-104, respectively. The DNA GC contents were calculated from a genome sequence to be 61.5% (KMM 9576T) and 61.4% (KMM 9553). Both strains contained the major ubiquinone Q-10 and C18:1ω7c as the dominant fatty acid followed by 11-methyl C18:1ω7c and C19:0 cyclo, and polar lipids consisted of phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, an unidentified aminophospholipid, and two unidentified phospholipids. Based on phylogenetic and phylogenomic analyses, and phenotypic characterization, strains KMM 9576T and KMM 9553 are concluded to represent a novel genus and species, for which the name Fererhizobium litorale gen. nov., sp. nov. is proposed. The type strain of the type species is strain KMM 9576T (=NRIC 0957T).

The effect of organic amendments on soil microbial activity and yield of faba bean (Vicia faba) inoculated with Rhizobium leguminosarum

A two year (2021 and 2022) field experiment was conducted to study the effect of organic amendments on soil microbial activity and yield of faba bean (Vicia faba L.) inoculated with Rhizobium leguminosarum at Savadkuh in the north of Iran as a factorial experiment based on a randomized complete block design with 3 replications. The treatments included seed inoculation at two levels (inoculation with Rhizobium leguminosarum bv. Viciae and non-inoculation) and fertilization at 5 levels [cattle manure (CM) @30 tonnes/ha, vermicompost of manure (VM) @20 tonnes/ha, vermicompost of Azolla (VA) @20 tonnes/ha, chemical fertilization based on soil analysis (NP), and control]. Present study found that the soil microbial biomass carbon (C) increased over time until 120 daysafter emergence (DAE). The maximum microbial biomass-C (441 mg/g soil) and bacterial count (545 × 105 cfu/ml) were obtained from the inoculated VA treatment. The highest yields of pods (14400 kg/ha) and seeds (1266 kg/ha) were obtained when the use of vermicompost was accompanied by inoculation of R. leguminosarum, so that in plants without inoculation, the use of vermicompost increased the yield of pods compared to the NP by 34% and compared to CM, it increased by 44%, but this increase was 39% and 19% for inoculated plants compared to NP and CM, respectively. Although the seeds of vermicomposted plants showed lower iron (Fe) content, they showed higher nitrogen (N), phosphorus (P), copper (Cu) and zinc (Zn) content than other plants. In total, the results showed a significant improvement in soil microbial activity, absorption of nutrients and bean yield by using vermicompost(especially VA) under R. leguminosarum inoculation. Therefore, in the low-fertile soils of Iran, the combined use of high-quality vermicompost together with R. leguminosarum can strengthen soil microbial activity and bean production and be a suitable alternative to chemical fertilizers.

Hydrogel capsules as new approach for increasing drying survival of plant biostimulant gram-negative consortium

Several plant growth–promoting bacteria (PGPB) are gram-negative, and their cell viability is affected during the bio-inoculant production. Hence, formulation-drying processes provide challenges that limit the adoption of these beneficial microorganisms in sustainable agricultural production. Among delivery system strategies for gram-negative PGPB, the encapsulating cells in biopolymeric materials are emerging as a promising alternative. This research aims to evaluate the effect of additives and crosslinking agents on the survival of the consortium of Herbaspirillum frisingense AP21, Azospirillum brasilense D7, and Rhizobium leguminosarum T88 in hydrogel capsules. Three crosslinkers and diverse potential drying protectors were tested. Calcium gluconate provides notable consortium survival advantages regarding colony-forming units (CFUs) (losses of up to 4 log CFU) compared to calcium lactate and calcium chloride (up to 6 log CFU). Additives such as skimmed milk, whey protein, and Gelita® EC improve the recovery of viable cells after the drying process, demonstrating an increase in cell survival of the three bacteria by up to 4 log CFU. The combination of these substances into a capsule prototype extends the storage stability of bacterial consortium up to 3 months at 18 ± 2 °C. This study expands the knowledge for formulating gram-negative PGPB consortium, regarding the crosslinker and drying protector relationship on encapsulation processes with drying survival and further storage stability performance.Key points• Hydrogel immobilization formulation approach for PGPB consortium• Enhancing drying survival of gram-negative PGPB consortium• Increasing storage stability of PGPB consortium at 18 °C

What determines symbiotic nitrogen fixation efficiency in rhizobium: recent insights into Rhizobium leguminosarum.

Symbiotic nitrogen fixation (SNF) by rhizobium, a Gram-negative soil bacterium, is an essential component in the nitrogen cycle and is a sustainable green way to maintain soil fertility without chemical energy consumption. SNF, which results from the processes of nodulation, rhizobial infection, bacteroid differentiation and nitrogen-fixing reaction, requires the expression of various genes from both symbionts with adaptation to the changing environment. To achieve successful nitrogen fixation, rhizobia and their hosts cooperate closely for precise regulation of symbiotic genes, metabolic processes and internal environment homeostasis. Many researches have progressed to reveal the ample information about regulatory aspects of SNF during recent decades, but the major bottlenecks regarding improvement of nitrogen-fixing efficiency has proven to be complex. In this mini-review, we summarize recent advances that have contributed to understanding the rhizobial regulatory aspects that determine SNF efficiency, focusing on the coordinated regulatory mechanism of symbiotic genes, oxygen, carbon metabolism, amino acid metabolism, combined nitrogen, non-coding RNAs and internal environment homeostasis. Unraveling regulatory determinants of SNF in the nitrogen-fixing protagonist rhizobium is expected to promote an improvement of nitrogen-fixing efficiency in crop production.