Search Results (71)

The development of new methods enhancing the growth and yield of cereals is still needed in crop production due to their great importance in human diet and as livestock fodder. In our study, new fertilizer-biostimulators with micro- and macroelements and extract containing lipochitooligosaccharides (LCOs) produced by Rhizobium leguminosarum bv. trifolii were used for stimulation of growth of barley and triticale in greenhouse conditions. The preparations were applied at the tillering and shooting stages, whereas plant traits were studied at flowering and at full maturity. The best results were recorded after the joint treatment of the plants with LCOs and mineral fertilization. The application of such a mixture significantly increased the length and mass of roots at flowering in both studied species. A beneficial effect of the treatment was also observed in barley and triticale yields. At full maturity, the grain mass per plant was significantly enhanced, which was the effect of an increased number of grains per ear and increased mass of 1000 grains. Full article

This study benchmarks two nanocellulose (NC) production architectures: sulfuric-acid hydrolysis of pineapple peel biomass to obtain hydrolyzed nanocellulose (HNC) and microbial biosynthesis of bacterial nanocellulose (BNC) by Rhizobium leguminosarum biovar trifolii in defined media. HNC and BNC were characterized by SEM, FTIR, AFM, and ζ-potential, and the routes were compared using a sustainability-focused multicriteria framework. The Visual Integration of Multicriteria Evaluation (VIME) (radar chart + weighted decision matrix) yielded a higher overall score for BNC (66) than HNC (51), driven primarily by lower downstream washing/neutralization water demand (~0.3 L vs. ~14 L per batch), fewer purification stages (~2 vs. ~5), and lower waste hazard. In contrast, HNC performed better in calendar time (~7 vs. ~18 days). AFM revealed route-dependent morphologies: BNC formed a homogeneous nanofiber network (37 ± 9 nm), while HNC formed heterogeneous lamellar fragments (70 ± 12 nm). Route-specific yields were 3.15% (w/w, dry biomass basis) for HNC and 1.065 g/L (culture-volume basis) for BNC. Although a full ISO-compliant Life Cycle Assessment (LCA) and Techno-Economic Analysis (TEA) are beyond the scope of this laboratory-scale study, the defined system boundaries and reported process inventories provide an LCA/TEA-ready template for future mass- and cost-balanced comparisons. Full article

Water deficit is a major constraint limiting the growth and yield of faba bean (Vicia faba L.). A pot experiment was conducted under controlled conditions to evaluate the effect of inoculation with Rhizobium leguminosarum bv. viciae BIHB 1148 (strain F14) and Pseudomonas alkylphenolica PF9 (strain L13) on faba bean drought resilience. Two irrigation regimes were applied: well-watered (80% of field capacity) versus water-stressed (40% of field capacity). Strain F14 was used to ensure effective biological nitrogen fixation, while strain L13 was applied in co-inoculation to evaluate its biostimulatory effects. The control plants received nitrogen in its chemical form. Results indicated that water deficit significantly (p < 0.001) reduced plant growth, nodulation, and photosynthesis-related parameters, and increased hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) levels, which are key markers of oxidative stress. However, co-inoculation with strains F14 and L13 significantly enhanced shoot and root biomass, as well as most agro-morphological traits. It also stimulated (p < 0.05) the antioxidant activities of superoxide dismutase (3-fold), guaiacol peroxidase (12%), and catalase (104%), and increased proline content (119%), which led to lower levels of MDA (54% decrease) and H₂O₂ (55% decrease), improved membrane stability, water status, and enhanced photosynthesis. Overall, co-inoculation of faba bean with Rhizobium leguminosarum bv. viciae BIHB 1148 and Pseudomonas alkylphenolica PF9 offers a promising and sustainable approach to improve plant resilience under water deficit. Full article

The study of wild relatives of crop legumes offers an inexhaustible source of useful properties and microorganisms for agriculture. In this study, we morphologically examined vavilovia (Vavilovia formosa (Steven) Fed.) nodules induced by strains of Rhizobium ruizarguesonis RCAM1026, Rhizobium leguminosarum sv. viciae TOM, as well as R. leguminosarum sv. viciae strains Vaf-12 and Vaf-108, isolated from nodules of wild-type plants of V. formosa. The nodules induced by R. leguminosarum sv. viciae strain Vaf-12 maintained histological and ultrastructural organization typical for indeterminate nodules. Different ultrastructural abnormalities were revealed in nodules induced by the other strains. When using the R. leguminosarum sv. viciae strain Vaf-108, pinkish nodules formed, in which a senescence zone developed in four weeks after inoculation. Furthermore, small brownish pseudonodules were also formed. In the nodules induced by the R. leguminosarum sv. viciae strain TOM bacteroids rapidly degraded and were excluded from the cytoplasm into the vacuole. Nodules induced by the R. ruizarguesonis strain 1026 were characterized with excessive accumulation of starch grains in mature infected cells. Full article

The uneven effectiveness of rhizobia inoculants has increased interest in developing specific inoculants for each genotype. This study investigated the biological nitrogen fixation efficiency and competition between different Rhizobium leguminosarum strains in different pea genotypes, namely, “Egle DS” and “Respect”. The results showed that plant genotype was a significant factor determining competition and nitrogen fixation among R. leguminosarum strains. The most competitive R. leguminosarum LIN06 strain in the pea genotype “Egle DS” was characterized by a low nitrogen fixation efficiency, while the most competitive R. leguminosarum EGLE10 strain in the “Respect” genotype was characterized by a high biological nitrogen fixation efficiency. It was also found that the “Respect” genotype may prefer and form symbiotic relationships with more efficient nitrogen fixing strains, while the “Egle DS” genotype formed symbiotic relationships with less efficient strains. However, even less efficient strains had a significant positive effect on nitrogen accumulation in plants under natural conditions. Finally, our study showed that sophisticated tests and methods are not necessary to analyze the competitiveness of rhizobia; it is sufficient to analyze the effectiveness of bacterial strains on plants in unsterilized soil. Full article

Faba bean is a high-protein legume that can be successfully grown in most climates around the world. It is one of the most popular pulses cultivated in Poland. Its seeds are a source of plant protein, used most often in feed production. Field experiments and laboratory seed analyses were carried out in 2022 and 2023 to assess the effect of the application of nitrogen-fixing bacteria on the yield and seed quality of a low-tannin faba bean cultivar. The factor was tested at four levels: control, seed inoculation with Rhizobium leguminosarum bv. viceae, foliar spraying with Methylobacterium symbioticum, and seed inoculation and spraying (double application). The application of N-fixing bacteria had a positive effect on faba bean seed yield. In 2022, plants responded most effectively to a double application, increasing seed yield by 25.4%, while, in 2023, the highest seed yield was obtained after inoculation (12.3% increase). Although the single application of bacteria caused a decrease in seed protein content, the double application (inoculation and spraying) significantly enhanced seed protein content. The protein productivity per hectare was compensated by the higher seed yield and increased by 41.7% in 2022 and 14.9% in 2023 compared to plots where N-fixing bacteria were not applied. This work shows that it is possible to use different strains of N-fixing bacteria in faba bean cultivation and this can significantly improve yields while reducing the need for synthetic nitrogen fertilizers, which supports sustainable production. Full article

Microbial exopolysaccharides (EPSs) are biopolymer materials with advantages such as biodegradability, biocompatibility, ease of mass production, and reproducibility. The EPS that was isolated from Rhizobium leguminosarum bv. viciae VF39 is an anionic polysaccharide with a backbone structure consisting of one galactose, five glucose molecules, and two glucuronic acids, along with 3-hydroxybutanoyl, acetyl, and pyruvyl functional groups. Through N-methyl-N′-nitro-N-nitrosoguanidine (NTG) mutagenesis, we isolated and purified a mutant EPS from VF39, VF39 #54, which demonstrated enhanced physicochemical and rheological properties compared to the wild-type VF39. The EPS structure of the VF39 #54 mutant strain showed a loss of glucuronic acid and 3-hydroxybutanoyl groups compared to the wild-type, as confirmed by FT-IR, NMR analysis, and uronic acid assays. The molecular weight of the VF39 #54 EPS was 250% higher than that of the wild-type. It also exhibited improved viscoelasticity and thermal stability. In the DSC and TGA analyses, VF39 #54 had a higher endothermic peak (172 °C) compared to the wild-type (142 °C), and its thermal decomposition point was 260 °C, surpassing the wild-type’s value of 222 °C. Additionally, the VF39 #54 EPS maintained a similar viscosity to the wild-type in various pH, temperature, and metal salt conditions, while also exhibiting a higher overall viscosity. The cytotoxicity test using HEK-293 cells confirmed that the VF39 #54 EPS was non-toxic. Due to its high viscoelastic properties, the VF39 #54 EPS shows potential for use in products such as thickeners, texture enhancers, and stabilizers. Furthermore, its thermal stability and biocompatibility make it a promising candidate for applications in food, pharmaceuticals, and cosmetic formulations. Additionally, its ability to maintain viscosity under varying environmental conditions highlights its suitability for industrial processes that require consistent performance. Full article

Multipartite genomes are thought to confer evolutionary advantages to bacteria by providing greater metabolic flexibility in fluctuating environments and enabling rapid adaptation to new ecological niches and stress conditions. This genome architecture is commonly found in plant symbionts, including nitrogen-fixing rhizobia, such as Rhizobium leguminosarum bv. trifolii TA1 (RtTA1), whose genome comprises a chromosome and four extrachromosomal replicons (ECRs). In this study, the transcriptomic responses of RtTA1 to partial nutrient limitation and low acidic pH were analyzed using high-throughput RNA sequencing. RtTA1 growth under these conditions resulted in the differential expression of 1035 to 1700 genes (DEGs), which were assigned to functional categories primarily related to amino acid and carbohydrate metabolism, ribosome and cell envelope biogenesis, signal transduction, and transcription. These results highlight the complexity of the bacterial response to stress. Notably, the distribution of DEGs among the replicons indicated that ECRs played a significant role in the stress response. The transcriptomic data align with the Rhizobium pangenome analysis, which revealed an over-representation of functional categories related to transport, metabolism, and regulatory functions on ECRs. These findings confirm that ECRs contribute substantially to the ability of rhizobia to adapt to challenging environmental conditions. Full article

Biological nitrogen fixation by rhizobia-nodulated legumes reduces the dependence on synthetic nitrogen fertilizers. Identification of locally adapted rhizobia may uncover economically valuable strains for sustainable agriculture. This study investigated the diversity and symbiotic potential of rhizobia associated with three Medicago species from Eastern Romania’s ecosystems. Phenotypic screening ensured that only rhizobial species were retained for molecular characterization. 16S rDNA sequencing clustered the isolates into four distinct groups: Sinorhizobium meliloti, Sinorhizobium medicae, Rhizobium leguminosarum, and Mesorhizobium spp. The chromosomal genes (atpD, glnII, recA) and nifH phylogenies were congruent, while the nodA phylogeny grouped the Mesorhizobium spp. isolates with R. leguminosarum. Medicago sativa was the most sampled plant species, and only S. meliloti and R. leguminosarum were found in its nodules, while Medicago falcata nodules hosted S. meliloti and Mesorhizobium spp. Medicago lupulina was the only species that hosted all four identified rhizobial groups, including S. medicae. This study provides the first report on the Mesorhizobium spp. associated with M. falcata nodules. Additionally, R. leguminosarum and two Mesorhizobium genospecies were identified as novel symbionts for Medicago spp. Comparative analysis of Medicago-associated rhizobia from other studies revealed that differences in 16S rDNA sequence type composition were influenced by Medicago species identity rather than geographic region. Full article

Biological nitrogen fixation in legume plants depends on the diversity of rhizobia present in the soil. Rhizobial strains exhibit specificity towards host plants and vary in their capacity to fix nitrogen. The increasing interest in rhizobia diversity has prompted studies of their phylogenetic relations. Molecular identification of Rhizobium is quite complex, requiring multiple gene markers to be analysed to distinguish strains at the species level or to predict their host plant. In this research, 50 rhizobia isolates were obtained from the root nodules of five different Pisum sativum L. genotypes (“Bagoo”, “Respect”, “Astronaute”, “Lina DS”, and “Egle DS”). All genotypes were growing in the same field, where ecological farming practices were applied, and no commercial rhizobia inoculants were used. The influence of rhizobial isolates on pea root nodulation and dry biomass accumulation was determined. 16S rRNA gene, two housekeeping genes recA and atpD, and symbiotic gene nodC were analysed to characterize rhizobia population. The phylogenetic analysis of 16S rRNA gene sequences showed that 46 isolates were linked to Rhizobium leguminosarum; species complex 1 isolate was identified as Rhizobium nepotum, and the remaining 3 isolates belonged to Rahnella spp., Paenarthrobacter spp., and Peribacillus spp. genera. RecA and atpD gene analysis showed that the 46 isolates identified as R. leguminosarum clustered into three genospecies groups (B), (E) and (K). Isolates that had the highest influence on plant dry biomass accumulation clustered into the (B) group. NodC gene phylogenetic analysis clustered 46 R. leguminosarum isolates into 10 groups, and all isolates were assigned to the R. leguminosarum sv. viciae. Full article

Cabbage serves as an important food and nutrition source for numerous communities in the world, yet its production requires substantial quantities of chemical fertilizers. In this study, we assessed the impact of both increasing nitrogen and phosphorus mineral (NP) fertilization, along with the application of plant growth-promoting bacteria (PGPB) on the N and P uptake, quality, and yield of cabbage. To this end, we conducted two consecutive field experiments following a randomized block design with four replicates and two factors: NP doses and PGPB inoculation. PGPB inoculation used a bacterial consortium comprising Azospirillum brasilense D7, Herbaspirillum sp. AP21, and Rhizobium leguminosarum T88. Our results showed a significant influence of both biofertilization and NP fertilization across both crop cycles; however, no interaction between these factors was observed. In the first crop cycle, 75% of NP mineral fertilization (equivalent to 93.6 kg ha⁻¹ of N and 82.1 kg ha⁻¹ of P) positively impacted yield and N uptake. Also, microbial inoculation significantly influenced crop yield, resulting in a 9-ton increase in crop yield per hectare due to biofertilization. In the second crop cycle, we observed a significant positive effect of mineral fertilization on cabbage yield and nutritional quality. The relative agronomic effectiveness (RAE) index showed that combining biological fertilization with 50% and 75% of the NP fertilization, respectively, increased yield by 66% and 48% compared to the commercial NP dosage without PGPB. Collectively, our results demonstrated that within our experimental setup, NP fertilization dosage can be reduced without any detrimental impact on yield. Moreover, biofertilization could enhance cabbage quality and yield in field conditions. Full article

Livestock production in Afghanistan highly relies on grazing and clover feed, which is a key component of pastures and forage crops. This study elucidated the genetic diversity of clover-nodulating rhizobia in different ecological regions and their effects on clover growth. A total of 57 rhizobia were isolated and their genetic diversities were studied through 16S rRNA and nifD genes. The isolates were inoculated to clover (Afghan local variety), to investigate the potential of nitrogen fixation and influences of clover growth. The 16S rRNA gene analysis showed two distinct groups of Rhizobium (94.7%) and Ensifer (5.3%) species. The nifD phylogenetic relationship revealed a high similarity to Rhizobium and a novel lineage group close to Rhizobium leguminosarum species. In the plant test, different genotypes significantly (p < 0.01) exhibited an increase in plant biomass production, compared to the un-inoculated plants. Among genotypes, the highest plant biomass was recorded in PC8 (1769.0 mg/plant) and PC9 (1409.2 mg/plant) isolates as compared to un-inoculated plants (144.0 mg/plant). Moreover, these isolates showed maximum nitrogen fixation rates of 8.2 and 6.5 µM/plant, respectively. These isolates were identified as the most promising rhizobial strains for developing biofertilizers in the context of Afghanistan. Full article

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. Full article

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. Full article

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. Full article