Bradyrhizobium Japonicum Strain Research Articles

Comparative genomic analysis of Bradyrhizobium strains with natural variability in the efficiency of nitrogen fixation, competitiveness, and adaptation to stressful edaphoclimatic conditions.

Bradyrhizobium is known for fixing atmospheric nitrogen in symbiosis with agronomically important crops. This study focused on two groups of strains, each containing eight natural variants of the parental strains, Bradyrhizobium japonicum SEMIA 586 (=CNPSo 17) or Bradyrhizobium diazoefficiens SEMIA 566 (=CNPSo 10). CNPSo 17 and CNPSo 10 were used as commercial inoculants for soybean crops in Brazil at the beginning of the crop expansion in the southern region in the 1960s-1970s. Variants derived from these parental strains were obtained in the late 1980s through a strain selection program aimed at identifying elite strains adapted to a new cropping frontier in the central-western Cerrado region, with a higher capacity of biological nitrogen fixation (BNF) and competitiveness. Here, we aimed to detect genetic variations possibly related to BNF, competitiveness for nodule occupancy, and adaptation to the stressful conditions of the Brazilian Cerrado soils. High-quality genome assemblies were produced for all strains. The core genome phylogeny revealed that strains of each group are closely related, as confirmed by high average nucleotide identity values. However, variants accumulated divergences resulting from horizontal gene transfer, genomic rearrangements, and nucleotide polymorphisms. The B. japonicum group presented a larger pangenome and a higher number of nucleotide polymorphisms than the B. diazoefficiens group, possibly due to its longer adaptation time to the Cerrado soil. Interestingly, five strains of the B. japonicum group carry two plasmids. The genetic variability found in both groups is discussed considering the observed differences in their BNF capacity, competitiveness for nodule occupancy, and environmental adaptation.IMPORTANCEToday, Brazil is a global leader in the study and use of biological nitrogen fixation with soybean crops. As Brazilian soils are naturally void of soybean-compatible bradyrhizobia, strain selection programs were established, starting with foreign isolates. Selection searched for adaptation to the local edaphoclimatic conditions, higher efficiency of nitrogen fixation, and strong competitiveness for nodule occupancy. We analyzed the genomes of two parental strains of Bradyrhizobium japonicum and Bradyrhizobium diazoefficiens and eight variant strains derived from each parental strain. We detected two plasmids in five strains and several genetic differences that might be related to adaptation to the stressful conditions of the soils of the Brazilian Cerrado biome. We also detected genetic variations in specific regions that may impact symbiotic nitrogen fixation. Our analysis contributes to new insights into the evolution of Bradyrhizobium, and some of the identified differences may be applied as genetic markers to assist strain selection programs.

Effects of nitrogen deposition on the rhizosphere nitrogen-fixing bacterial community structure and assembly mechanisms in Camellia oleifera plantations.

Increased nitrogen deposition is a key feature of global climate change, however, its effects on the structure and assembling mechanisms of the nitrogen-fixing bacteria present at the root surface remain to be elucidated. In this pursuit, we used NH4NO3 to simulate nitrogen deposition in a 10-year-old Camellia oleifera plantation, and set up four deposition treatments, including control N0 (0 kg N hm-2 a-1), low nitrogen N20 (20 kg N hm-2 a-1), medium nitrogen N40 (40 kg N hm-2 a-1) and high nitrogen N160 (160 kg N hm-2 a-1). The results showed that nitrogen deposition affected the soil nitrogen content and the structure of the nitrogen-fixing bacterial community. Low nitrogen deposition was conducive for nitrogen fixation in mature C. oleifera plantation. With increasing nitrogen deposition, the dominant soil nitrogen-fixing bacterial community shifted from Desulfobulbaceae to Bradyrhizobium. When nitrogen deposition was below 160 kg N hm-2 a-1, the soil organic matter content, total nitrogen content, nitrate nitrogen content, ammonium nitrogen content, urease activity, soil pH and nitrate reductase activity influenced the composition of the nitrogen-fixing bacterial community, but the stochastic process remained the dominant factor. The results indicate that the strains of Bradyrhizobium japonicum and Bradyrhizobium sp. ORS 285 can be used as indicator species for excessive nitrogen deposition.

Polyglycerol citrate: A novel coating and inoculation material for soybean seeds

The microbial inoculation of legumes such as soybeans is crucial for thriving plant growth due to symbiotic nitrogen (N) fixation and biological plant N fertilization. Soybean requires microbial pre-inoculation before sowing using the rhizobia strain Bradyrhizobium japonicum. Peat is typical for this purpose, although not sustainable since it is a finite resource. Here, we propose a straight-forwarding route to prepare and apply polyglycerol-citrate polymer (PGC), a biodegradable and fully renewable polymer, as a carrier for Bradyrhizobium japonicum inoculants for soybeans. This novel eco-friendly polymer combines the advantages of a polymeric, water-soluble structure based on biopolymers, which can protect the inoculant cells during the seed inoculation process, with protective properties of glycerol for bacterial cells and the contribution of citric acid for metabolic processes. A greenhouse study was conducted using soybean seeds coated with three different proportions of PGC with B. japonicum planted in a sand substrate free of external interference. Comparative results of N content and δ15N signature in soybean plant parts calculated from the natural abundance method associated with viability tests showed equal or superior symbiotic performance and nitrogen fixation rates to peat-based inoculants, considered the gold-standard carrier for inoculants. It ensured the shelf life of the inoculant formulations, offering convenience for farmers and environmental benefits through reduced fertilization.

Pyrolysis temperature affects biochar suitability as an alternative rhizobial carrier

Biochars produced from different feedstocks and at different pyrolysis temperatures may have various chemical and physical properties, affecting their potential use as alternative microbial carrier materials. In this study, biochars were produced from pine wood and oak feedstocks at various temperatures (400°C, 500°C, 600°C, 700°C and 800°C), characterized, and assessed for their potential as carriers for Bradyrhizobium japonicum (CB1809) strain. The biochars were then stored at two different storage temperatures (28°C and 38°C) for up to 90 days. Furthermore, the study also explored the role of potentially ideal carriers as inoculants in the growth of Glycine max L. (soybean) under different moisture levels i.e., 55% water holding capacity (WHC) (D0), 30% WHC (D1) and, 15% WHC (D2) using a mixture of 50% garden soil and 50% sand. The results were compared to a control group (without inoculants) and a peat inoculant. Among all the materials derived from pine wood and oak, pine wood biochar pyrolyzed at 400℃ (P-BC400) exhibited the highest CFU count, with values of 10.34 and 9.74 Log 10 CFU g− 1 after 90 days of storage at 28℃ and 38℃, respectively. This was notably higher compared to other biochars and peat carriers. Significant (p < 0.05) increases in plant properties: shoot and root dry biomass (174% and 367%), shoot and root length (89% and 85%), number of leaves (71%), membrane stability index (27%), relative water content (26%), and total chlorophyll (140%) were observed in plants treated with P-BC400 carrier inoculant compared to the control at D2; however, lower enrichment of δ13C (37%) and δ15N (108%) with highest number of root nodules (8.3 ± 1.26) and nitrogenase activity (0.869 ± 0.04) were observed under D2, as evident through PCA analysis, showing more nitrogen (N) fixation and photosynthetic activity. Overall, this experiment concluded that biochar pyrolyzed at lower temperatures, especially P-BC400, was the most suitable candidate for rhizobial inoculum and promoted soybean growth.

COMPLEX INOCULATION OF SOYBEANS WITH NODULE BACTERIA BRADYRHIZOBIUM JAPONICUM AS A MEASURE TO OPTIMIZE SYMBIOTIC NITROGEN FIXATION

Objective. Establish effective mixed inoculants for soybeans based on new active strains of Bradyrhizobium japonicum with different intensity and dynamics of nitrogen-fixing activity to improve nodulation processes and functional activity of legume-rhizobia symbiosis. Methods. Microbiological, physiological, statistical, gas chromatography. Legume-rhizobia systems based on Glycine max L. (Merill) soybean, variety Samorodok, were studied using recombinant strains of B. japonicum: B199, B201, Д47, Д48, Д52, Д60, Д63. Monoinoculation of soybean with B. japonicum 634б served as the control. Results. Mixed inoculation of B. japonicum ensured positive ontogenetic dynamics of root nodule formation in soybean. The indicator of the number of root nodules in experimental plants was 1.2–1.9 times higher versus the control plants from Day 18 to 45 of soybean vegetation. When soybeans were inoculated with B. japonicum 634б + B201 and 634б + Д 52, the mass of nodules at Day 45 of vegetation increased by 30.0–35.3 % versus the control and was the highest (1.10–1.15 g/plant) among the studied variants, as a result of the strengthening effect of complex bacterization. A positive synergistic effect of the combined use of strains was obtained — intensification of the nitrogen-fixing activity of soybean root nodules. In the phase of budding/beginning of flowering and full flowering under combined inoculation with active strains of B. japonicum 634б + Д47, 634б + Д52 and 634б + В201, nitrogen fixation of soybean nodules increased by 10.7–25.5 % (at Day 32), by 13.2–30.9 % (at Day 38), and was also 2.3–2.8 times higher in the phase of full flowering (Day 45 of soybean vegetation) versus the similar indicator of control plants. In the phase of full flowering of plants (Day 45 of vegetation), under mixed inoculation with strains of B. japonicum 634б + Д47, 634б + В201, 634б + Д52 and В201 + Д52, the aboveground mass of plants exceeded that of control plants by 8.3–17.2 % variant, which was probably provided by improved conditions of their nitrogen nutrition, due to enhanced assimilation of N2 by root nodules. The most developed root system was in soybeans inoculated with strains B. japonicum 634б and B. japonicum 634б + Д52, B. japonicum 634б + В201 and B. japonicum Д48 + Д52. Conclusion. Symbiotic features of active recombinant strains of B. japonicum and their variability in functional activity at different stages of soybean ontogenesis should be taken into account when creating complex nitrogen-fixing bacterial preparations for soybeans with the effect of microbiological synergy.

Viability of Nodule Bacteria Bradyrhizobium japonicummon Soybean Seeds by Treatment With Fungicides During Extended Storage

Background. With the increase in soybean cultivation areas, inoculants are becoming increasingly sought after. They are not only compatible with the original preparations for seed treatment of soybean but also offer the possibility of applying them for several days or even months before sowing into the soil. Objective. The viability of new strains of nodule bacteria Bradyrhizobium japonicum (strain PC07 and strain B78) was investigated on the surface of soybean seeds treated with fungicides Fever and Maxim XL during the extended storage of inoculated seeds. Additionally, their ability for nitrogen fixation under symbiotic conditions was evaluated. Methods. Сultivation, serial dilution method, determination of bacterial titer of inoculants, quantification of colony forming units (CFU), gas chromatography. Results. In laboratory conditions, on the soybean seeds of Almaz and Vasylkivska varieties, the viability of the nodule bacteria B. japonicum PC07 and B78, which are more resistant to the active substances of these fungicides in pure culture, decreased. This reduction was dependent on the storage period, the fungicide used, and the strain of inoculant. One day after inoculation on the seeds without the use of fungicide, 68.6–75.4% CFU of the initial number was retained. Seeds treated with the fungicide Fever contained 36.5–38.3% CFU, and those treated with Maxim XL contained 26.2–27.0% CFU. The use of inoculants based on fungicide-resistant strains of B. japonicum PC07 and B78 also provided high cell viability – 2.41–2.8×106 (on the seeds without treatment), 1.40–1.70×106 (with Fever) and 0.8–1.17×106 (with Maxim XL) CFU/seed after 5 days of storage. The nitrogen-fixing activity of root nodules in soybean plants of Almaz and Vasylkivska varieties, whose seeds were treated with Fever, decreased on both varieties by 18.4–22.4% and 32.1–39.5%, respectively and for treatment with Maxim XL, the reduction was 24.5–33.7% and 47.7–75.2%, respectively, during the storage of seeds for 5 and 7 days before sowing, compared to control variants (seeds without fungicide treatment). Conclusions. The utilization of fungicide-resistant strains of B. japonicum PC07 and B78 for bacterization of soybean seeds treated with fungicides Fever and Maxim XL provides a high inoculation titer during 5 days of storage. Viability of microbial cells on seeds treated with fungicides significantly diminishes during storage for more than 7–14 days. Insufficient titer of CFU of B. japonicum strains PC07 and B78 on the seed surface after 14 days of storage can considerably impede the efficacy of biopreparations. Therefore, it is crucial to seek substances that can enhance the resistance of rhizobia on seeds to the adverse effects of fungicide seed treatment, ensuring a longer period of their viability.

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.

Features of Local Bradyrhizobia Populations after Long-Term Period in the Soil without a Host Plant

In previous years, the serological and genetic diversities of soybean nodule bacteria in agrocenoses of Ukraine have been researched. Less attention was paid to the study of their survival in the soil. Taking into account the natural heterogeneity of bacteria of the genus Bradyrhizobium, the aim of this work was to evaluate the diversity of bradyrhizobia in local populations of different soils after a long-term period without leguminous plants, to obtain new isolates of nodule bacteria and to study their properties. Methods. Microbiological (isolation of bradyrhizobia from the nodules of trap plants, study of the properties of strains), serological (study of the diversity of rhizobia in nodule populations, study of the serological affiliation of strains), vegetation and field experiments (study of plant infecting with bradyrhizobia). Results. Local populations of bradyrhizobia in sod-podzolic soil and leached chornozem were studied using trap plants of the genera Glycine, Vigna, and Lupinus. It was established that after a 7 to 8-year period without leguminous plants, active nodule bacteria remained in both types of soil, which nodulated cultivated and wild soybeans, cowpeas, mung beans, adzuki beans, and lupine. The main microsymbionts of plants of the genera Glycine and Vigna on different types of soil were soybean bradyrhizobia belonging to 6 serological groups: 46, M8, КВ11, 634b, HR, and B1. The representatives of 4 serogroups corresponded to the inoculant strains of Bradyrhizobium japonicum 46, M8, 634b, and КВ11, which were periodically used in the studied areas. In addition to B. japonicum, cowpea plants trapped microsymbionts of B. lupini serogroup 367a (4.2%) from the soil. Bradyrhizobia of serogroup B1 were detected both in nodules of cowpea (6.3%) and wild soybean (12.5%). 45.8% of lupine nodules were formed by bacteria B. lupini of serogroup 367a. The appearance in populations of representatives of serogroups HR and B1 along with a group of unidentified microsymbionts requires further research. Cultivation of trap plants of wild soybeans and various types of cowpea made it possible to identify saprophytic strain B. japonicum M8 (formed 25.0% to 83.4% of nodules) in the sod-podzolic soil, which did not infect the roots of cultivated soybeans. 70 isolates of bradyrhizobia were obtained from nodules of trap plants, which were preliminarily identified as B. japonicum, B. lupini, and Bradyrhizobium sp. Conclusions. The results confirm the importance of using different leguminous trap plants for a more complete characterization of the local rhizobial community. Cultivation of plants of the genera Glycine, Vigna, and Lupinus, capable of cross-infection, made it possible to detect bacteria B. japonicum (serogroups 46, M8, КВ11, 634b, HR), B. lupini (serogroup 367a), and Bradyrhizobium sp. (serogroup B1), which exist for a long-term period as saprophytes in sod-podzolic soil and leached chornozem. 70 isolates of bradyrhizobia were obtained, 35 of which were serologically related to the inoculant strains of B. japonicum introduced into the agrocenosis at the beginning of the research.

Genetic diversity assessment and selection of Bradyrhizobium strains for Inceptisols based on symbiotic performance

The symbiotic association of pigeonpea (Cajanus cajan (L.) Millsp.) with rhizobia plays a pivotal role in plants’ growth and development. The present study was carried out at Institute of Agricultural Sciences, Banaras Hindu University, Varanasi, Uttar Pradesh during 2018–2020 to explore the diversity of rhizobia present in the Cajanus cajan root under Inceptisols and identify an elite strain that exhibits exceptional plant growth promotion and of nitrogenase activity for efficient nitrogen fixation. The bacterial identification using 16s rDNA sequencing revealed bacteria strains Bradyrhizobium japonicum (S12), Bradyrhizobium subterraneum (S1, S7, S8, S10, S13), Bradyrhizobium yuanmingense (S2, S3, S4, S6, S9, S11) while two bacteria were the endophytes identified as Pseudomonas azotoformans (S5) and Paenibacillus seodonensis (S15). Genetic diversity using UPGMA clustering revealed remarkable genetic variations, classifying 14 strains into three primary clusters and four secondary clusters. Strains S1, S3, S6, S9, and S13 exhibited elevated nitrogenase activity, indicative of their proficient nitrogen fixation capability. In plant growth experiments, all strains demonstrated significant growth of the plants compared to control. The notable growth enhancement by these five strains can be attributed to their remarkable efficiency in nitrogen fixation, as indicated by significantly higher nodule formation and nitrogenase activity. These findings provide valuable insights for identifying potential rhizobial inoculants to enhance pigeonpea productivity.

Impact of nitrogen-fixation bacteria on nitrogen-fixation efficiency of Bambara groundnut [Vigna subterranea (L) Verdc] genotypes.

Nitrogen fixation by bacteria is essential for sustaining the growth, development, and yield of legumes. Pot experiments were carried out at the International Institute of Tropical Agriculture (IITA) in the glasshouse between August to December 2018/2019 cropping season in Ibadan, Nigeria. Field studies were also performed in two different agroecological zones, "Ibadan and Ikenne" between August and December of 2019/2020 cropping season. The studies were set up to determine the potential of nitrogen-fixation bacteria strain inoculation on the nitrogen-fixation potential of 10 Bambara groundnut (BGN) genotypes, namely, TVSu-378, TVSu-506, TVSu-787, TVSu-1,606, TVSu-1,698, TVSu-1739, TVSu-710, TVSu-365, TVSu-475, and TVSu-305. The strains were inoculated as a broth to seedlings of each BGN genotype in the pot experiment. While six seeds from each BGN genotype were coated with each of the following nitrogen-fixation bacteria (Bradyrhizobium japonicum strains), FA3, USDA110, IRJ2180A, and RACA6, nitrogen fertilizer (urea, 20 kg/ha) was applied as a check to the nitrogen-fixation bacteria to seedlings of BGN genotypes 2 weeks after planting in both glasshouses and fields. Uninoculated plants served as controls (zero inoculation and zero fertilization). The field experiments were arranged in Randomized Complete Block Design (RCBD), while the glasshouse experiments were arranged in Complete Randomized Design (CRD) in triplicate. The result gotten showed that higher nodule numbers and weight were recorded in TVSu-1739 and TVSu-475 in both locations and seasons compared to other genotypes; the highest nitrogen fixed values were recorded among BGN genotypes TVSu-1739, TVSu-1,698, TVSu-787, TVSu-365, TVSu-305, TVSu-710, and TVSu-1,606, with a range of (62-67 kg ha-1), and were mostly enhanced by RACA6 and USDA110 strains compared to other strains that were used.

Genetic variation and genetic complexity of nodule occupancy in soybean inoculated with USDA110 and USDA123 rhizobium strains

BackgroundSymbiotic nitrogen fixation differs among Bradyrhizobium japonicum strains. Soybean inoculated with USDA123 has a lower yield than strains known to have high nitrogen fixation efficiency, such as USDA110. In the main soybean-producing area in the Midwest of the United States, USDA123 has a high nodule incidence in field-grown soybean and is competitive but inefficient in nitrogen fixation. In this study, a high-throughput system was developed to characterize nodule number among 1,321 Glycine max and 69 Glycine soja accessions single inoculated with USDA110 and USDA123.ResultsSeventy-three G. max accessions with significantly different nodule number of USDA110 and USDA123 were identified. After double inoculating 35 of the 73 accessions, it was observed that PI189939, PI317335, PI324187B, PI548461, PI562373, and PI628961 were occupied by USDA110 and double-strain nodules but not by USDA123 nodules alone. PI567624 was only occupied by USDA110 nodules, and PI507429 restricted all strains. Analysis showed that 35 loci were associated with nodule number in G. max when inoculated with strain USDA110 and 35 loci with USDA123. Twenty-three loci were identified in G. soja when inoculated with strain USDA110 and 34 with USDA123. Only four loci were common across two treatments, and each locus could only explain 0.8 to 1.5% of phenotypic variation.ConclusionsHigh-throughput phenotyping systems to characterize nodule number and occupancy were developed, and soybean germplasm restricting rhizobium strain USDA123 but preferring USDA110 was identified. The larger number of minor effects and a small few common loci controlling the nodule number indicated trait genetic complexity and strain-dependent nodulation restriction. The information from the present study will add to the development of cultivars that limit USDA123, thereby increasing nitrogen fixation efficiency and productivity.

Symbiotic interaction between a mixture of Bradyrhizobium japonicum strains and different soybean cultivars

Aim. To study the mutual relations between different soybean cultivars and two Bradyrhizobium japonicum strains after mixed inoculation, to evaluate the impact of the introduced microorganisms on the local rhizobial communities in soil, the formation and functioning symbiotic systems, and productivity of soybean. Methods. Microbiological and serological methods; field experiment, gas chromatography and mathematical-statistical methods. Results. A small- plot field experiment demonstrated that the use of a mixture of B. japonicum 46 and B. japonicum КВ11 strains pro- moted a more even distribution of the local and introduced rhizobia in the nodule populations of 12 soybean cultivars of different geographic origin. There was no domination of particular strains in the nodules, and the symbiotic systems formed were more balanced than the control without inoculation. After inoculation of the above-mentioned mixture, in most cultivars there was a considerable increase in the number of nodules (10–45 % more) and their mass (11–86 % increase). There was also an increase in the level of symbiotic nitrogen fixation with 1.2–4.2 times and an increase in the weight of grain per plant by 6–29 % (depending on the cultivar). The efficiency of a mixture of B. japonicum 46 and КВ11 strains in a preparation Rizogumin was confirmed in extensive field trials with soybean on an area of about 60 thousand ha in different regions of Ukraine. In the background of the local populations of the soybean nodulating bacteria in the areas, the application of the formulated mixture of the two rhizobia strains ensured a stable increase by 15–33 % in the soybean yield as compared with the control without the inoculation. Conclusions. A novel approach was investigated, which lies in the application of a mixture of B. japonicum 46 (genetic group USDA 6) and B. japoni- cum КВ11 (genetic group USDA 123) strains for different soybean cultivars inoculation. Combining these two strains and their introduction into agrocenoses ensured the formation of a balanced symbiotic systems (without clear domina- tion of some strains in the nodules). This was expressed in an intensified nodulation, symbiotic nitrogen fixation, and increased yield of different cultivars of soybeans by 15–33 % as compared to the control (without inoculation).

Yield response of accessions of Bambara groundnut (Vigna subterranea (L) Verdc) inoculated with Bradyrhizobium japonicum strains

Field experiments were conducted in two different agroecological locations of Ibadan and Ikenne in Nigeria from August through December during the 2019 and 2020 cropping seasons. The studies were set up to reduce reliance on inorganic nitrogen fertilizer and to embrace the use of nitrogen-fixing bacteria to improve legume production to increase farmers' output and profitability. Ten accessions of the Bambara groundnut (BGN) were used in the trials. Seeds of each BGN accession were coated with each of the following Bradyrhizobium japonicum strains (B. japonicum): FA3, RACA6, USDA110, and IRJ2180A before planting. Furthermore, Nitrogen (N) fertilizer (20 kg/ha, urea) was applied to seedlings without inoculation, and uninoculated seedlings (without inoculation and without fertilization) served as control. The experiment was, therefore, a factorial arrangement (10 BGN accessions, 4 B. japonicum strains, N fertilizer application, and an uninoculated control). The yield and yield components of the inoculated BGN accessions were significantly enhanced at both agroecological locations and seasons. Among the B. japonicum strains used for inoculation, RACA6 strains significantly enhanced the yield and yield component of TVSu-1698 than other inoculated BGN accessions with a mean value of 6,234 ± 87 kg ha−1 recorded in both locations and seasons, compared to the result obtained in the combination of TVSu-1698 with N fertilizer with a mean value of 3,264 ± 943 kg ha−1. By using TVSu-1698 with RACA6 strain, farmers can get 85% more yield than on average with other genotypes/strains combination, while an average yield of 60% could be obtained by farmers using N fertilizer application.

Bradyrhizobium japonicum IRAT FA3 promotes salt tolerance through jasmonic acid priming in Arabidopsis thaliana

BackgroundPlant growth promoting rhizobacteria (PGPR), such as Bradyrhizobium japonicum IRAT FA3, are able to improve seed germination and plant growth under various biotic and abiotic stress conditions, including high salinity stress. PGPR can affect plants’ responses to stress via multiple pathways which are often interconnected but were previously thought to be distinct. Although the overall impacts of PGPR on plant growth and stress tolerance have been well documented, the underlying mechanisms are not fully elucidated. This work contributes to understanding how PGPR promote abiotic stress by revealing major plant pathways triggered by B. japonicum under salt stress.ResultsThe plant growth-promoting rhizobacterial (PGPR) strain Bradyrhizobium japonicum IRAT FA3 reduced the levels of sodium in Arabidopsis thaliana by 37.7%. B. japonicum primed plants as it stimulated an increase in jasmonates (JA) and modulated hydrogen peroxide production shortly after inoculation. B. japonicum-primed plants displayed enhanced shoot biomass, reduced lipid peroxidation and limited sodium accumulation under salt stress conditions. Q(RT)-PCR analysis of JA and abiotic stress-related gene expression in Arabidopsis plants pretreated with B. japonicum and followed by six hours of salt stress revealed differential gene expression compared to non-inoculated plants. Response to Desiccation (RD) gene RD20 and reactive oxygen species scavenging genes CAT3 and MDAR2 were up-regulated in shoots while CAT3 and RD22 were increased in roots by B. japonicum, suggesting roles for these genes in B. japonicum-mediated salt tolerance. B. japonicum also influenced reductions of RD22, MSD1, DHAR and MYC2 in shoots and DHAR, ADC2, RD20, RD29B, GTR1, ANAC055, VSP1 and VSP2 gene expression in roots under salt stress.ConclusionOur data showed that MYC2 and JAR1 are required for B. japonicum-induced shoot growth in both salt stressed and non-stressed plants. The observed microbially influenced reactions to salinity stress in inoculated plants underscore the complexity of the B. japonicum jasmonic acid-mediated plant response salt tolerance.

Efficient control of the productivity of agrophytocenosis of soybean (Glicyne max (L.) Merill)

Around the world, there is a surging demand for soy, the ‘king of beans’. Soy is a globally traded foodstuff produced in both temperate and tropical regions and is a major source of protein and vegetable oils. In the conditions of the Kaliningrad region, the duration of soybean vegetation in soddy-weakly podzolic gleyic light loamy soil, with the medium reaction close to neutral, high and very high content of mobile phosphorus, and exchangeable potassium attains 144 days. The agrophytocenosis productivity is controlled through application of different mineral and bacterial fertilizers. Analysis of variance of the experimental data obtained in the study showed a pronounced relationship of 0.71 for the effect of the fertilizer system on quantitative indicators of the biological yield of soybean seeds. The effectiveness of the microbial-plant system of soybean cultivar Merlin and strains of nodule bacteria Bradyrhizobium japonicum, under optimal conditions, increased the crop yield to 4.43 t/ha, which is 2.11 t/ha higher compared to the control and 1.01 t/ha higher relative to the experimental option with carbamide fertilizer.

The Role of Trehalose-producing Bradyrhizobium japonicum and Azotobacter chroococcum in Enhancing Salinity Tolerance of Zea mays Plants

Salinity is one of the most potent abiotic elements in nature and is damaging to both plants and microbes. Osmostress response in bacteria involves the accumulation of small organic compounds called compatible solutes as trehalose. In this work the synthesis and accumulation of trehalose by Bradyrhizobium japonicum strain (ARC 517) were investigated. Different sources of carbon, nitrogen, initial pH, and inoculum level were studied in order to increase trehalose productivity. An optimal production medium containing glucose and yeast extract was found suitable for trehalose production. The results showed that keeping the pH of the culture broth at 6.0 is important for trehalose production. Moreover the optimal level of inoculum was 4.0%. The optimized parameters gave a maximum trehalose production of 22.65 mg ml-1. Scanning electron microscope showed that cells of B. japonicum that enhanced for trehalose was aggregated and became the longest with length about 3 times higher than that of control. The results of field experiment revealed that, the Zea mays plants treated with B. japonicum strain (ARC 517) that enhanced for trehalose + Azotobacter chroococcum retained higher relative water content (RWC), chlorophyll content, K+/Na+ ratio as compared to other treatments. Positive correlation between trehalose overproduction and high-yield parameters were observed under saline conditions. These findings suggest that trehalose overproduction could be a beneficial characteristic for biofertilizers.

Soybean growing under inoculation by Bradyrhizobium japonicum strains in the Forest-steppe and Steppe zones of Ukraine

Soybean growing under inoculation by Bradyrhizobium japonicum strains in the Forest-steppe and Steppe zones of Ukraine

Symbiotic and physiological indicators of soybean inoculated of Bradyrhizobium japonicum single-strain in 7 days before sowing

Results of investigation of soybean of the Almaz variety in inoculation with preparations based on nodule bacteria Bradyrhizobium japonicum (Kirchner, 1896), Jordan, 1982 B78, B157, D37, D87 are presented. Different periods of the soybean seeds inoculation were used - on the sowing day (control) and in 7 days before sowing (experimental variants). The differences between control and experimental plants in the formation and functioning of the symbiotic apparatus and its functional activity, depending on the period between from seed inoculation to sowing were analysed. It was determined that the number of root nodules in the control plants was higher. The mass of nodules at the stage of 3 true leaves exceeded the control by 1.5–2.0 times in plants inoculated in 7 days before sowing, and the intensity of nitrogen fixation by 1.7–6.6 times. At the budding-beginning of flowering stage, the mass and intensity of N2 fixation by the nodules of control plants increased. As a result, the difference between the nitrogen fixing activity of control and experimental plants decreased significantly. Stimulating effect on aboveground mass of Bradyrhizobium japonicum strains with increased nitrogen fixing activity was noted. Optimal conditions for the formation and functioning of bean-rhizobial symbiosis were provided at the use of both of these terms of soybean inoculation. This reveals the possibility of effective application of early inoculation of soybean seeds with preparations based on nodule bacteria Bradyrhizobium japonicum active strains.

Effect of Bradyrhizobium japonicum Strains and Inorganic Nitrogen Fertilizer on the Growth and Yield of Bambara Groundnut (Vigna subterranea (L.) Verdc) Accessions

This study was set up to compare the inoculation of Bradyrhizobium japonicum strains and the application of nitrogen (N) fertilizers (urea with 46% nitrogen) on the growth and yield of Bambara groundnut accessions. The study results suggest that the benefits of Bradyrhizobium japonicum (B. japonicum) strain inoculation are greater and that the strain could reduce reliance and the excess amount spent by farmers to procure inorganic fertilizers and avoid the negative effect of N fertilizer on the environment after its use. Field studies were conducted in two different geographical locations, in Ibadan (Ib) and Ikenne (Ik), Nigeria, during the rainy season between August and December in 2019 and 2020. The experiment was arranged in a randomized complete block design (RCBD) in both locations and seasons and was replicated three times, with each block representing each replicate. It had a 10 × 6 factorial arrangement with one block holding the 10 accessions of Bambara groundnut inoculated with four B. japonicum strains. The second block had N fertilizer application and the third control block was without inoculation or fertilizer application. The 10 accessions of Bambara groundnut used in the study were as follows: TVSu-378, TVSu-506, TVSu-787, TVSu-1606, TVSu-1698, TVSu-1739, TVSu-710, TVSu-365, TVSu-475, and TVSu-305. Six seeds of each accession were coated with each of the four B. japonicum strains, namely, FA3, USDA110, IRJ2180A, and RACA6, before planting them in the field in both locations during the rainy season. In the next block, urea as N fertilizer (46% nitrogen) was applied to the uninoculated seedlings of accessions of Bambara groundnut 2 weeks after planting (WAP). The third block was the control with zero inoculation and zero fertilizer application. Data collected were subjected to an analysis of variance and mean and were separated using Duncan's Multiple Range Test (DMRT) at a p &amp;gt; 0.05 level of probability. It was found that FA3 inoculation significantly enhanced the growth traits of the accessions than other strains and N fertilizer application. In both locations and seasons, at 7 weeks after planting (WAP) and 12 WAP, plant height (19.54 and 22.71 cm), number of branches (33.63 and 62.77), number of leaves (116.54 and 209.25), terminal leaf length (5.62 and 6.00 cm), and width (2.09 and 2.56 cm) were recorded. The yield and yield components recorded at harvest were as follows: pod length (13.27 cm), pod width (9.08 mm), seed length (9.39 mm), seed width (6.92 mm), weight of 100 seeds (56.85 g), and yield/ha (750.72 kg). The yield and yield components were also significantly influenced by the inoculation of FA3 and RACA6 than other inoculated strains and N fertilizer application in both locations and seasons.

Revealing potential functions of hypothetical proteins induced by genistein in the symbiosis island of Bradyrhizobium japonicum commercial strain SEMIA 5079 (= CPAC 15).

BackgroundBradyrhizobium japonicum strain SEMIA 5079 (= CPAC 15) is a nitrogen-fixing symbiont of soybean broadly used in commercial inoculants in Brazil. Its genome has about 50% of hypothetical (HP) protein-coding genes, many in the symbiosis island, raising questions about their putative role on the biological nitrogen fixation (BNF) process. This study aimed to infer functional roles to 15 HP genes localized in the symbiosis island of SEMIA 5079, and to analyze their expression in the presence of a nod-gene inducer.ResultsA workflow of bioinformatics tools/databases was established and allowed the functional annotation of the HP genes. Most were enzymes, including transferases in the biosynthetic pathways of cobalamin, amino acids and secondary metabolites that may help in saprophytic ability and stress tolerance, and hydrolases, that may be important for competitiveness, plant infection, and stress tolerance. Putative roles for other enzymes and transporters identified are discussed. Some HP proteins were specific to the genus Bradyrhizobium, others to specific host legumes, and the analysis of orthologues helped to predict roles in BNF.ConclusionsAll 15 HP genes were induced by genistein and high induction was confirmed in five of them, suggesting major roles in the BNF process.Supplementary informationThe online version contains supplementary material available at 10.1186/s12866-022-02527-9.