The rhizosphere is a critical hotspot of plant-microbe interactions, where Plant Growth-Promoting Rhizobacteria (PGPR) play key roles in nutrient mobilization, growth promotion and stress tolerance. This study aimed to isolate and characterize PGPR from the rhizosphere of chilli ( Capsicum annuum L.). Twenty-three morphologically distinct isolates were obtained and evaluated through morphological, biochemical, enzymatic and molecular approaches. Most isolates exhibited catalase and nitrate reduction activities, while carbohydrate utilization profiles revealed broader metabolic versatility in Lysinibacillus macroides compared to Lysinibacillus fusiformis . Enzymatic screening uncovered a high prevalence of protease, urease, amylase, cellulase and lipase production, key traits linked to nutrient cycling and rhizosphere colonization. Quantitative assessment of protease and lipase activities revealed significant inter-isolate variation, with isolates 4.1 and 2.B exhibiting comparatively higher enzyme indices. Pot tray validation showed that rhizobacterial inoculation enhanced seed germination and early seedling growth, with isolates 4.1 and 2.B performing best. Molecular identification confirmed isolates 4.1 and 2.B as L. fusiformis and L. macroides , respectively, supported by phylogenetic analysis. The dominance of diverse rhizobacterial strains and their hydrolytic enzyme activities reflects their ecological adaptability in semi-arid soils. These findings highlight L. fusiformis and L. macroides as promising biofertilizer candidates for chilli cultivation, offering eco-friendly alternatives to chemical fertilizers and contributing to sustainable, climate-resilient agriculture. • Twenty-three chilli rhizobacteria were screened morphologically and biochemically. • L. fusiformis and L. macroides exhibited strong PGPR and multi-enzyme activity. • High metabolic versatility supported efficient nutrient mobilization. • 16S rRNA analysis confirmed both isolates as potential biofertilizer candidates.

A novel PGPR Streptomyces sp. for efficient phthalate biodegradation: Mechanistic insights and application in contaminated soil.

Tea (Camellia sinensis) is a globally significant economic crop, and its desirable quality and health benefits are largely credited to catechin derivatives. Plant growth-promoting rhizobacteria (PGPR), such as Bacillus velezensis, are well-known for enhancing the environmental fitness and disease resistance of plants. However, the regulation of their impact on tea catechin biosynthesis remains unclear. While previous studies have focused on PGPR-facilitated growth promotion in crops like tomatoes and rice, the physiological mechanisms by which microbes regulate secondary metabolism in tea-especially under co-inoculation conditions-remain largely underexplored. This study examined the effects of B. velezensis SD24, isolated from tea rhizosphere soil, on catechin derivative accumulation of tea leaves by altering gene expression and the rhizosphere microbiome. Strain SD24 exhibited broad-spectrum antimicrobial activity against various pathogens due to behaving antimicrobial gene clusters. Tea plants inoculated with SD24 showed significantly increased levels of catechin derivatives in their leaves. This was likely achieved by upregulation of leucoanthocyanidin reductase and anthocyanidin reductase within the phenylpropanoid pathway. Additionally, chlorophyll content was increased. Transcriptomic analysis revealed a notable enrichment in biosynthesis of secondary natural products among the tea genes activated by SD24 inoculation. Metagenomic analysis further demonstrated that SD24 inoculation led to a restructuring of the tea rhizosphere microbiome. Notably, co-inoculation with Piriformospora indica, a beneficial endophytic fungus, suppressed SD24-induced gene expression and catechin accumulation, underscoring its antagonism toward SD24. These findings suggest that B. velezensis SD24 enhances tea quality, probably by transcriptionally activating the synthesis of catechin derivatives, a process associated with the restructuring of the rhizosphere microbiome.IMPORTANCEThe mechanisms through which plant growth-promoting rhizobacteria (PGPR) influence secondary metabolism in perennial crops remain poorly understood. This study demonstrates that Bacillus velezensis SD24, a tea rhizosphere isolate, significantly enhances the accumulation of health-beneficial catechin derivatives in tea leaves. This quality improvement is associated with transcriptionally upregulating key biosynthetic genes (LAR and ANR) and concurrently restructuring the rhizosphere microbiome. Furthermore, we reveal a critical antagonistic interaction, where the beneficial fungus Piriformospora indica suppresses these SD24-induced effects. Our findings provide crucial insights into how specific PGPR strains may directly enhance tea quality by affecting host plant metabolism and the root microbiome, highlighting the complex and tailored microbial interactions that could be harnessed for sustainable agriculture.

In conclusion, the present study provides preliminary functional insights into the role of OsbHLH in promoting plant growth under low-nutrient conditions. Ectopic expression of OsbHLH in Arabidopsis was associated with improved plant performance at morphological, physiological, biochemical, and molecular levels under sub-optimal nutrient regimes. Taken together, the study indicates that OsbHLH could be a key component of the regulatory framework of plant-PGPR interactions and nutrient stress responses; further targeted studies are required to conclusively establish its precise functional role and underlying mechanisms. Plant growth-promoting rhizobacteria (PGPR) enhance plant performance under environmentally adverse conditions. In the present study, we analyzed the functional relevance of OsbHLH (OsbHLH63) gene that was notably upregulated in rice following SN13 inoculation under nutrient-deficient conditions. Ectopic expression of OsbHLH in Arabidopsis thaliana resulted in improved growth, and enhanced physio-biochemical attributes under nutrient-deficient conditions. Transgenic plants also exhibited modifications in tissue organization, cellular structure, and lignification patterns. Gene expression analysis revealed differential expression of genes involved in nutrient uptake and transport (IRT1, PHR1, ZNE, NRT, and KUP), lignin biosynthesis (CAD1, CCR1, and COMT), and carbohydrate metabolism (PK1, PEPC1, GDH, FBP, and ENO). Additionally, GC-MS-based metabolomic profiling revealed 40 significantly affected metabolites associated with galactose metabolism, propanoate metabolism, amino acid biosynthesis, the pentose phosphate pathway, the TCA cycle, and glycolysis/gluconeogenesis. Collectively, these findings affirm the potential involvement of OsbHLH in nutrient stress adaptation and in recapitulating key aspects of SN13-induced responses observed in rice, although further targeted investigations are required to validate its regulatory function in plant-microbe interactions and stress tolerance.

Fusarium oxysporum causes damping-off disease in Pinus massoniana seedlings. While Trichoderma koningiopsis can enhance seedling resistance by regulating rhizosphere plant growth-promoting rhizobacteria (PGPR), the specific bacterial compositions and their role in disease resistance remained undefined. To elucidate this mechanism, we used amplicon and metagenomic sequencing to identify T. koningiopsis-assembled PGPR. Synthetic PGPR communities were constructed from isolated strains to validate their effects on disease suppression and growth promotion. Microbial community analysis indicated that T. koningiopsis reshaped the bacterial community: Actinospica, Dyella, and Streptomyces decreased in presence, and Bacillus and Arthrobacter increased. A total of 153 PGPR strains were isolated from the T. koningiopsis-inoculated treatment. Of these, eight strains demonstrated significant inhibitory effects against F. oxysporum, ranging from 33.81% to 59.52%. Four synthetic communities (SynComs) (C1, C2, HT, and 2K) were further constructed, exhibiting superior inhibitory effects against F. oxysporum compared to individual strains. Compared to the control, the C2 and HT SynComs increased seedling height by 10.18% and 9.44%, and reduced disease incidence by 50% and 36.67%, respectively. These treatments also enhanced protective enzyme activity and alleviated membrane damage. At the molecular level, the C2 and HT SynComs boost plant resistance by modulating the plant hormone and mitogen-activated protein kinase (MAPK) signaling pathways, thereby activating the expression of crucial resistance genes such as PR1, FLS2, and CAT1. Trichoderma koningiopsis alters the composition of rhizosphere PGPR community. The synthetic PGPR community assembled under the influence of T. koningiopsis effectively enhances damping-off resistance and promotes the growth of Masson pine seedlings. © 2026 Society of Chemical Industry.

Soil salinization, a growing global issue threatening sustainable agriculture, can be mitigated by Plant Growth-Promoting Bacteria (PGPB) as a green strategy. PGPB primarily consist of plant growth-promoting rhizobacteria (PGPR) and plant growth-promoting endophytes (PGPE). Numerous studies have demonstrated that both types of bacteria can enhance plant performance under salt stress through various mechanisms that help maintain ion homoeostasis, improve osmotic adjustment, and enhance antioxidant defence. Although PGPR and PGPE share highly conserved core mechanisms, their distinct colonisation niches lead to functional divergence in efficacy, stability, and ecological roles. This review systematically summarises these conserved mechanisms for enhancing plant salt tolerance. Furthermore, it elaborates on their functional differences across various ecological niches and discusses the major challenges and future directions for the field application of these PGPB. Ultimately, this review aims to provide a theoretical foundation for the scientific deployment of PGPB in saline agroecosystems.

Halotolerant plant growth-promoting rhizobacteria (PGPR) represent a promising strategy for enhancing crop productivity in degraded soils. This study evaluated 51 bacterial strains isolated from the rhizosphere of the Saharan halophyte Phragmites communis L. for their capacity to improve the performance of wheat (Triticum aestivum L.) and pepper (Capsicum annuum L.) under nutrient-deficient sandy soil conditions. The selection of halotolerant isolates was based on their potential for cross-tolerance, assuming that their adaptive mechanisms against salinity could also mitigate the osmotic and nutritional constraints inherent to nutrient-poor sandy substrates. Two strains, XE-15 and XR-18, were selected based on in vitro screening and tentatively assigned to the genera Pseudomonas and Bacillus, respectively, using 16S rRNA sequencing and multilocus sequence analysis (MLSA). Greenhouse experiments demonstrated that bacterial inoculation significantly increased plant biomass (up to ~2-fold compared to control) and enhanced pepper fruit yield (0.68 g vs. 0.20 g in control). XR-18 notably increased Fe (up to 198.65 mg kg−1) and P (7.98 mg kg−1) accumulation in wheat, while XE-15 exhibited substantial concentrations of nitrogen (1.08%) and magnesium (4.11 mg kg−1) and zinc (102.3 mg kg−1). Soil properties were also improved, including increased water-holding capacity (~30%) and enhanced micronutrient availability. Zinc showed the most pronounced strain-specific response, increasing by 84% under XE-15 and by more than 160% under XR-18. However, taxonomic resolution remains tentative in the absence of genome-level analyses, and mechanistic insights are primarily inferred from in vitro traits. The simplified greenhouse system further limits ecological interpretation. These findings highlight the potential of halotolerant PGPR in degraded soils while emphasizing the need for genomic validation, mechanistic studies, and field-scale evaluation.

Plant growth-promoting rhizobacteria (PGPR) represent a sustainable strategy to enhance crop productivity, the multi-omics regulatory mechanisms underlying their growth-promoting effects in garlic remain poorly understood. In this study, we integrated physiological, phytohormone metabolomic, and transcriptomic analyses to systematically elucidate the growth-promoting mechanism of Pseudomonas sp. strain UW4 in garlic. Our results demonstrated that UW4 inoculation significantly improved aboveground morphological traits, including plant height, leaf length, leaf width, and pseudostem thickness, and optimized root system architecture by increasing total root length, root surface area, and root tip number. These morphological improvements were accompanied by enhanced photosynthetic pigment accumulation and increased biomass production. Phytohormone profiling revealed that UW4 inoculation elevated the levels of auxin (indole-3-acetic acid, IAA) and its precursors (L-tryptophan and tryptamine), while significantly reducing the content of 1-aminocyclopropane-1-carboxylic acid (ACC), the precursor of ethylene biosynthesis. Transcriptomic analysis identified 687 differentially expressed genes (DEGs), which were significantly enriched in auxin and ethylene signaling pathways. Mechanistically, UW4 upregulated the expression of SAUR (Small auxin-up RNA) to promote IAA synthesis, and suppressed the transcription of ethylene biosynthesis-related genes. Additionally, the downregulation of PYL (Pyrabactin resistance 1-like) genes indicated that UW4 also modulates the abscisic acid (ABA) signaling pathway. Quantitative real-time PCR (qRT-PCR) validation confirmed that the expression of ACO (ACC oxidase), a key rate-limiting enzyme in ethylene synthesis, was significantly downregulated in UW4 groups. Collectively, our findings demonstrate that UW4 optimizes garlic growth and yield potential by coordinately regulating auxin, ethylene, and ABA metabolism and gene expression, providing a theoretical foundation and elite microbial resource for the green and high-yield cultivation of garlic.

Arsenic contamination threatens rice (Oryza sativa) production, yet the synergistic use of iron plaque (IP) and root-associated biofilms as a rhizosphere barrier to limit arsenic uptake remains unexplored. To address this, we engineered an arsenic-resistant (AR) plant growth-promoting rhizobacterium (AR-PGPR), Bacillus subtilis p43-Taglo1, expressing the speciation-inert arsenic-binding protein TaGlo1. In a contaminated paddy, this strain increased grain yield by 10.7-11.6% and reduced grain arsenic by 28.2-37.4% compared to the wild-type. The engineered strain robustly colonized roots and enhanced the formation of a functional IP-biofilm composite, which sequestered more arsenic. This was driven by a 2.87-fold increase in Fe(II) oxidation and elevated production of extracellular polymeric substances (EPS) (1.4-fold) and siderophores (1.5-fold). Transcriptomic analysis revealed that inoculation upregulated bacterial genes for Fe(II) oxidation, siderophore, and EPS biosynthesis, while in rice roots, it activated phytohormone pathways and downregulated arsenite transporters (OsLsi1 and OsLsi2). We conclude that AR-PGPR can restore beneficial root-microbe interactions under arsenic stress. The IP-biofilm composite acts as an inducible barrier essential for the dual benefits of arsenic exclusion and growth promotion. Our study shows that AR rhizobacteria fortify the IP-biofilm composite to reduce arsenic uptake and promote rice growth, providing a route toward safer rice production in arsenic-affected regions.

Biofertilizers used in saleable formulations perform poorly in cold Himalayan regions owing to the suppressed metabolic activity of bioinoculants under low temperatures. Cold-adapted Actinobacteria, as potent plant growth-promoting rhizobacteria (PGPR), emerge as viable cold-active bioinoculants for sustainable nutrient management in high-altitude crop cultivation. This perspective aims to document the Actinobacterial metabolic diversity in the glacier bionetwork lying in the North-Eastern and North-Western Himalayan region. A comparative functional bioinformatics study of plant growth-promoting genes demonstrated distinct clustering of Himalayan versus non-Himalayan strains, driven by alanine/aspartate/glutamate metabolism, geraniol degradation, and pyruvate metabolism. This pioneering genomic differentiation of Himalayan actinomycetes from other cold habitats highlights unique cold-tolerance and plant growth-promoting factors that may target particular functionality for crop cultivation in the extreme glacier environment.

Role of silver nanoparticles and Bacillus cereus in modulating growth, photosynthetic activity, and antioxidant responses in sorghum under cobalt stress.

Dual efficacy of chromium (Cr) tolerant Pseudomonas aeruginosa and indole-3-acetic acid (IAA) in conferring Cr tolerance to eggplant via improved growth and physiological aspects.

Plant growth-promoting rhizobacteria (PGPR) enhance plant growth and development through diverse mechanisms, including phytohormone production, nutrient acquisition, and stress mitigation. This study describes the isolation and characterization of two bacterial strains, DT1 and S10, from the rhizospheres of Diplotaxis tenuifolia and Cynodon dactylon, respectively that exhibit multiple plant growth‑promoting traits, including phosphate and zinc solubilization, nitrogen metabolism and the production of indole acetic acid (IAA) and siderophores. Using whole genome sequencing and taxonomic analyses, these two strains were identified as Acinetobacter calcoaceticus (DT1) and Citrobacter braakii (S10). Functional genomic annotation revealed numerous genes associated with key plant growth-promoting traits, including those involved in indole-3-acetic acid (IAA) (trpABCDE, ipdC), cytokinin (miaABE), and riboflavin biosynthesis, which were further supported by targeted metabolomic analyses. In addition, genes associated with nitrogen metabolism, including nitrate/nitrite reduction (nirB, narGHI), as well as phosphate solubilization (gcd, phoARP, pstABCS, pqqEFG) were identified and supported by phenotypic assays. Interestingly, biosynthetic gene clusters for the secondary metabolites enterobactin, bacillibactin, and staphyloferrin B, known to contribute to plant growth promotion, were identified in both genomes. Both strains also harbored genes potentially involved in stress-related metabolic processes. Furthermore, non-targeted metabolomic analysis revealed that DT1 and S10 produced a range of intracellular and extracellular metabolites associated with plant growth promotion and stress resilience, including cadaverine, biotin, arginine, and GABA. Collectively, these findings position DT1 and S10 as promising bioinoculant candidates, offering an integrative genomic and metabolic foundation for their application in next-generation sustainable agricultural strategies.

Synergistic plant-driven transformations of Fe minerals, organic carbon, and microbial communities initiate pedogenesis in Fe tailings for sustainable rehabilitation.

The intensive use of synthetic fertilizers and pesticides has increased crop productivity but also contributed to soil degradation and biodiversity loss, highlighting the need for more sustainable agricultural strategies. Among emerging solutions, plant growth-promoting rhizobacteria (PGPR), particularly members of the Bacillota phylum, are gaining attention as effective bioinoculants that enhance plant growth and tolerance to biotic and abiotic stresses. However, introduced strains do not function in isolation. They enter complex microbial communities, shaped by plant type and developmental stage, influenced by soil properties and environmental conditions. While the positive effects of PGPR on plant performance are well documented, their impact on indigenous rhizosphere microbiota remains less studied. This review synthesizes current knowledge on how Bacillota-based inoculants influence native microbial communities in cereals, vegetables, orchard crops, and fiber plants. Most studies report shifts toward plant-beneficial taxa and reduced abundance of potential pathogens following Bacillota application. Frequently enriched genera include Bacillus, Pseudomonas, Lysobacter, Sphingomonas, Streptomyces, Azotobacter, Arthrobacter, Pseudarthrobacter, Bradyrhizobium, Devosia, Flavobacterium, Klebsiella, Herbaspirillum, and Rhodanobacter. These changes are often associated with improved plant growth and yield, and stress resilience. However, responses strongly depend on strain, plant and methodological approach. We summarize commonly applied approaches used to assess these interactions. Despite technological advances, limitations remain, such as single time-point sampling, simplified experimental systems, and insufficient integration of inoculant persistence with community analyses. Standardized, multi-site experimental frameworks, with multiple sampling terms are needed to improve predictability and ensure the safe implementation of PGPR-based solutions in sustainable agriculture.

We present the findings from the genome sequencing project of a plant growth-promoting rhizobacterium Pseudomonas inefficax MG-2, sourced from rhizospheric soil. The genome spans 5,736,804 base pairs with an average GC content of 62.9%. An incomplete plasmid with a length of 16,324 base pairs and a GC content of 52.6% was also identified.

Erwinia persicina (Ep) is recognized as an emerging pathogen of considerable threat to tomato yields. Although Stenotrophomonas rhizophila (Sr) has long been recognized as a plant growth-promoting rhizobacterium (PGPR), the use of this PGPR has sometimes been constrained by the rhizosphere stress factor in the biocontrol of the pathogen. This study investigated the potential of biogenic gold nanoparticles (AuNPs) to enhance the performance of Sr. through bio-conjugation. Biogenic AuNPs were synthesized and conjugated with S. rhizophila (Sr-AuNPs). The physical and biochemical stability of the conjugate was verified via TEM, DLS, and FTIR. Greenhouse trials were conducted across three independent growing seasons to evaluate the impact of the Sr-AuNP conjugate (T3) on tomato growth, yield, and resistance against E. persicina infection (T4) compared to healthy controls (T1) and non-conjugated bacteria (T2). Bio-conjugation facilitated robust root surface colonization, with FESEM-EDS confirming AuNP persistence (7.1–10.2 wt.%) on the root epidermis. The T3 treatment consistently demonstrated superior disease suppression, maintaining the lowest Disease Severity Index (DSI) values (0.65–0.80) throughout the study. Agronomically, T3 was the only treatment that sustained the highest statistical order (Tukey group ‘a’) in terms of fruit weight throughout the three seasons, reaching 204.62 g in Season 3, which was a remarkable threefold increase from the infected control T4 (72.52 g). These results indicate that AuNPs act as a supporting scaffold that promotes the longevity and efficacy of PGPR. Interestingly, rather than acting solely as a plant growth promoter, the bio-conjugate functioned chiefly as a potent disease suppressor and plant growth stabilizer under high pathogen pressure. This biologically derived method presents itself as a sustainable solution to the threat presented by emergent phytopathogens in contemporary agriculture.

Global climate change and increasing water scarcity pose significant threats to melon production, particularly in semi-arid regions where drought stress severely limits plant growth and yield. To address these challenges through sustainable microbial interventions, this two-year field study evaluated the effects of different Plant Growth-Promoting Rhizobacteria (PGPR), including Bacillus subtilis, Bacillus megaterium, Enterococcus spp., and their consortium, on plant growth, yield, and leaf nutrient composition of melon (Cucumis melo L. cv. Kırkağaç 637) under irrigated and non-irrigated conditions. PGPR applications generally improved vegetative growth parameters, such as stem diameter, main stem length, and leaf number, compared with the control, with Bacillus subtilis consistently showing the most pronounced effects across both growing seasons. Under non-irrigated conditions, Enterococcus spp. application resulted in a marked increase in plant fresh weight compared with the control. Although total fruit yield was not significantly affected by PGPR treatments, leaf nutrient analysis revealed that Bacillus subtilis significantly enhanced magnesium (Mg) and iron (Fe) contents under both irrigation regimes. These findings indicate that PGPR, particularly Bacillus subtilis, can improve vegetative growth and nutrient uptake of melon plants and contribute to alleviating the adverse effects of drought stress, highlighting their potential role in sustainable melon production under water-limited conditions.

Plant growth-promoting rhizobacteria (PGPR) are beneficial bacteria that directly or indirectly enhance plant growth, crop yields and stress tolerance. In this study, the maize variety ‘Ningdan 33’ was used as the experimental material. Strain PW2, isolated from salinized soil in Yinchuan, Ningxia, was identified as Enterobacter asburiae based on morphological, physiological, and biochemical characteristics as well as 16S rRNA gene sequencing. Pot experiments demonstrated its potential for salt tolerance and growth promotion in maize. The strain can grow in environments with 2.0%–10.0% NaCl and at pH 8.0–11.0, while exhibiting multiple plant growth-promoting traits, such as nitrogen fixation, potassium solubilization, siderophore production, ACC deaminase activity, and IAA synthesis. Under salt stress conditions, inoculation with PW2 significantly promoted maize seed germination, seedling growth, and root system development. Compared to the control group, inoculation with PW2 suspension significantly increased plant height, root length, nitrogen content, and the fresh and dry weights of both shoots and roots. Furthermore, PW2 inoculation significantly enhanced antioxidant enzyme activities in maize leaves and roots. Specifically, the activities of POD, SOD, and CAT in leaves increased by 92.75% (p = 4.0×10-7), 21.79% (p = 0.008), and 17.28% (p = 0.010), respectively, while those in roots increased by 54.32% (p = 2.0×10-6), 19.36% (p = 0.041), and 37.80% (p = 0.002), respectively. Conversely, the MDA content in leaves and roots decreased by 19.53% (p = 0.0058) and 32.91% (p = 0.006), respectively. Additionally, the contents of soluble sugar, soluble protein, and proline in both leaves and roots increased significantly. Collectively, these results indicate that strain PW2 effectively mitigates oxidative damage caused by salt stress through enhanced antioxidant defense and improved osmotic regulation, thereby promoting maize growth.

Nitrogen (N) is a key nutrient for upland rice (Oryza sativa L.), and plant growth-promoting rhizobacteria (PGPR) have been investigated as a sustainable strategy to improve plant nutrition and crop performance. This study evaluated the effects of N topdressing and PGPR inoculation on leaf chlorophyll index (LCI), leaf nutrient concentrations, and yield components in upland rice. A field experiment was conducted in a randomized block design (4 × 6 factorial) with four N rates (0, 40, 80, and 120 kg ha−1) and five PGPR strains (Azospirillum brasilense, Nitrospirillum amazonense, Bacillus subtilis, Priestia aryabhattai, and Methylobacterium symbioticum), plus a non-inoculated control. No significant interaction between N rates and PGPR inoculation was observed. Nitrogen increased leaf phosphorus (P), potassium (K), and magnesium (Mg) concentrations and panicle number; however, it also increased unfilled grains, reduced grain weight, and did not affect grain yield. Azospirillum brasilense increased LCI by 25.7%. Bacillus subtilis and A. brasilense increased leaf N, K, Mg, copper (Cu) and manganese (Mn) concentrations. Azospirillum brasilense, B. subtilis, N. amazonense, and P. aryabhattai reduced unfilled grains, increased grain weight and grain yield by up to 10.7%, whereas M. symbioticum did not differ from the control in grain yield. Under the conditions of this study, nitrogen was not limiting for grain yield, and all strains, except M. symbioticum, were associated with increases in grain yield and changes in plant nutritional status.