Search Results (874)

Spearmint is a medicinal and aromatic crop vulnerable to several diseases, and its cultivation relies heavily on chemical inputs, which can alter phytonutrient quality and raise environmental and health concerns. To address this, the current study focused on developing a safe bioformulation to promote growth and natural defense in spearmint. The bioformulation is based on four plant growth-promoting rhizobacteria (PGPR), Bacillus aryabhathai, Brevibacterium frigoritolerans, Bacillus vallismortis, and Pseudomonas frederiksbergensis, encapsulated in 2% natural alginate. The compositional, structural, and morphological properties of alginate powder and beads were characterized. The beads were evaluated for encapsulation efficiency, bacterial survival, release, and degradation in soil. The bioformulation was applied to the rhizosphere of spearmint and was assessed for its effects on plant growth and natural defenses. Extracted alginate exhibited high purity and structural integrity, and encapsulation efficiency reached 99.99%, providing long-term protection and bacterial viability while regulating their release. The encapsulated consortium notably increased the number of branches, height, and biomass in spearmint. Additionally, a potential induction of plant defense response was observed, as indicated by increased phenylalanine ammonia-lyase activity, higher phenolic compound levels, and lignin accumulation in the roots and shoots of treated plants. These findings highlight the biostimulating effects of these four PGPR encapsulated in alginate on spearmint’s defense and growth. Full article

Extreme temperatures, drought, and salinity are among the most detrimental abiotic stressors limiting global plant productivity, and their frequency has intensified under climate change. These escalating pressures underscore the need for sustainable biological strategies that enhance plant resilience to climate-induced abiotic stresses. Plant growth-promoting rhizobacteria (PGPR) have emerged as a promising, eco-friendly solution due to their ability to optimize rhizospheric processes that strengthen plant adaptive capacity. PGPR improve nutrient acquisition, maintain ionic homeostasis, modulate phytohormone signaling, and regulate ethylene levels through ACC deaminase activity. They also stimulate antioxidant defenses, promote osmolyte and exopolysaccharide synthesis, and enhance root system development—key traits that collectively alleviate drought, salinity, and heat stress. Recent research demonstrates that co-inoculation, multi-strain microbial consortia, and synthetic communities designed using multi-omics approaches significantly enhance PGPR stability, colonization, and functional effectiveness under field conditions. Additionally, nanotechnology-enabled formulations and smart delivery systems are emerging as innovative tools to improve PGPR survival and targeted release in harsh environments. This review synthesizes current insights into PGPR-mediated stress mitigation, highlights technological innovations that support their application, and outlines pathways for integrating PGPR into climate-resilient, sustainable agricultural systems to safeguard crop productivity amid escalating environmental stress. Full article

Excessive nitrogen (N) fertilization in maize (Zea mays L.) production causes environmental degradation, particularly in semi-arid regions where high chemical inputs are necessary to maintain crop production. Plant growth-promoting rhizobacteria (PGPR) could reduce the optimal N fertilization doses. This investigation aimed to isolate bacteria, screen them for plant growth-promoting traits, and evaluate their potential effects on maize grain under different chemical N fertilization doses. Isolates Stenotrophomonas maltophilia LIMN and Enterobacter roggenkampii LCMG demonstrated multifunctional growth-promoting traits in vitro, including N₂ fixation, indole-3-acetic acid and siderophore production, potassium solubilization, and desiccation tolerance, with E. roggenkampii LCMG also solubilizing inorganic phosphate. A field trial across four chemical N fertilization rates (0, 40, 80, and 120 kg N ha⁻¹) revealed that single bacterial inoculation without N fertilizer matched or exceeded uninoculated controls receiving up to 80 kg of N ha⁻¹ (the standard recommendation). Specifically, S. maltophilia LIMN combined with the recommended rate of 80 kg N ha⁻¹ achieved the maximum grain yield (4601.2 kg DM ha⁻¹), outperforming uninoculated controls (without PGPR) receiving excessive fertilization at 120 kg N ha⁻¹ (3760.4 DM ha⁻¹). Although maize plants benefited from inoculation with S. maltophilia LIMN or E. roggenkampii LCMG, achieving similar or better yields than crops fertilized with high chemical N inputs under stress factors such as deficiency of moisture, low-nutrient soils, and high temperatures, the present study did not test the pathogenicity and biosecurity of S. maltophilia or E. roggenkampii in crops; therefore, the results are not a direct recommendation of their use as biofertilizers before novel studies to assess all the limitations and the potential to reduce N dependency in order to design novel sustainable strategies for crop production. Full article

The rhizosphere microbiome, the plant’s “second genome” is pivotal for crop nutrient acquisition, health, and stress responses. While fertilization ensures high agricultural yields, a key challenge is reshaping this microbiome to boost crop performance. This review synthesizes how mineral, organic, and bio-organic/microbial inoculant fertilizers affect rhizosphere microbial structure, diversity, and function. Long-term excessive mineral fertilizers (especially nitrogen) reduce microbial diversity, diminish beneficial groups (e.g., diazotrophs, PGPR), and disrupt microbial networks via soil acidification and altered root exudates, causing continuous cropping obstacles. In contrast, organic fertilizers improve soil microenvironments, maintaining high microbial diversity, enriching beneficial taxa (e.g., Proteobacteria, Actinobacteria), and enhancing community complexity. Bio-organic fertilizers/microbial inoculants “engineer” the microbiome by introducing exogenous beneficial microbes (e.g., Bacillus, Pseudomonas, AMF), directly promoting growth, suppressing diseases, and “reconditioning” indigenous beneficial communities. We also clarify how fertilization regulates plant-microbe dialog via root exudates and rhizosphere chemistry (e.g., pH, ion balance), discuss current challenges (causality, lab-to-field translation, genotype-microbiome-fertilization interactions), and outline future directions. Integrating rhizosphere microbiome management into fertilization is crucial for reducing chemical fertilizer reliance and advancing agricultural green transformation. Full article

Global climate change has intensified prolonged droughts, making the development of sustainable agricultural technologies essential. Although potassium humate (KH) and Bacillus aryabhattai (BA) are recognized individually as effective biostimulants, their joint application represents an innovative, unexplored complementary strategy to mitigate drought stress in cowpea (Vigna unguiculata L. Walp.). This study aimed to evaluate the effects of these bio-inputs on mitigating water stress in the cowpea (Vigna unguiculata L. Walp.) cultivar ‘BRS Verdejante’. The experiment was conducted under greenhouse conditions using a completely randomized design in a 2 × 8 factorial arrangement, with two water regimes (100% and 50% crop evapotranspiration—ETc) and eight biostimulant combinations of KH and BA. While BA alone (T4) intensified osmotic adjustment via proline accumulation and APX activation, the combined treatment T5 (10 mg kg⁻¹ soil KH + 4 mL kg⁻¹ seed BA containing 1 × 10⁸ CFU mL⁻¹) achieved the best overall performance under drought (50% ETc). T5 effectively enhanced superoxide dismutase activity, preserved leaf relative water content, and reduced cell membrane electrolyte leakage by 42.6% compared to untreated stressed plants. These physiological adaptations protected reproductive organs, resulting in a 51.6% increase in pod number per plant under drought. The strategic co-application of low-dose potassium humate (10 mg kg⁻¹ soil) and B. aryabhattai (4 mL kg⁻¹ seed) effectively regulates osmotic and oxidative homeostasis, maintaining pod formation (+51.6%) and securing cowpea grain yield per plant under drought stress, thus serving as a promising strategy to mitigate drought stress in cowpea under controlled greenhouse conditions. Full article

Aquaponics combines aquaculture and hydroponics, offering an integrated and sustainable food production system. This study investigated the probiotic properties, plant growth-promoting (PGP) activity, and nitrifying capacity of twelve lactic acid bacteria (LAB) strains isolated from an aquaculture farm environment on the Ivory Coast for their potential application in aquaponic systems. All isolates demonstrated antagonistic activity against key pathogenic indicator strains, except Vibrio cholerae, and displayed varying levels of surface hydrophobicity (5.50 ± 0.70% to 22.83 ± 1.17%) and auto-aggregation (32.50 ± 0.08% to 52.89 ± 0.39%) after 24 h. Antioxidant activity was significantly higher in cell-free supernatants (~71–79%) than in intact cells (~30–33%). Bile salt tolerance (0.3%, 4 h) ranged from 2.13 ± 0.76% to 40.87 ± 2.12%, and survival under pH 1.5 with pepsin for 3 h varied from 4.84 ± 0.26% to 53.98 ± 13.28%. All isolates produced lactic, acetic, citric, malic, and propionic acid and exhibited amylase and cellulase activity; none showed hemolytic activity. Only LAB 11 produced indole-3-acetic acid (17.72 ± 0.06 μg/mL), siderophores, and phosphate-solubilization activity for PGP traits, and this group significantly enhanced maize seed germination (86.66 ± 5.77%) and radicle length (7.00 ± 0.52 mm) compared to the control (63.33 ± 32.14% and 4.94 ± 1.52 mm), respectively. LAB 1 and LAB 10 demonstrated the highest ammonia-oxidizing capacity in vitro and in trout pond water. LAB 1, LAB 10, and LAB 11 were confirmed by whole genome sequencing analysis to be Enterococcus faecalis strains with a favorable-safety genomic profile and probiotic characteristics. These three strains therefore represent promising candidates for consortium-based applications in aquaponics systems. Full article

Pistachio (Pistacia vera L.) is among the most economically important nut crops worldwide. They are increasingly exposed to the environmental constraints associated with climate change, including drought, salinity, nutritional imbalances, and heightened disease pressure. These stressors compromise plant growth, physiological performance, nutrient acquisition, and orchard productivity, highlighting the need for sustainable strategies to enhance crop resilience. This review critically examines the current knowledge on the functional roles of arbuscular mycorrhizal fungi (AMF) and plant growth-promoting rhizobacteria (PGPR) in pistachio production. Evidence indicates that AMF and PGPR contribute to plant performance through multiple complementary mechanisms, including improved nutrient mobilization and uptake, maintenance of ionic homeostasis, enhancement of water-use efficiency, stimulation of antioxidant defenses, modulation of stress-related signaling pathways, and suppression of phytopathogens. AMF primarily enhance phosphorus acquisition, water relations, and soil structural stability, whereas PGPR contribute to nutrient solubilization, biological control, and induction of plant defense responses. Despite promising experimental results, most studies have been conducted under controlled conditions, limiting the translation of microbial inoculation strategies to commercial orchards in the field. We identified the key knowledge gaps and research priorities required to improve the consistency, scalability, and field validation of microbiome-based approaches for sustainable pistachio production under increasingly challenging environmental conditions. Full article

Drought mitigation by plant growth-promoting rhizobacteria (PGPR) is commonly assessed using individual physiological traits, although plant responses to water deficit are intrinsically multivariate. We developed a Multitrait Physiological Drought Mitigation Index (PDMI) to summarize PGPR-specific physiological responses in strawberry (Fragaria × ananassa) while separating drought-specific effects from general performance under optimal moisture. The balanced two-season experiment comprised 240 plant-level observations and 10 complete matched replication sets per season. The primary PGPR analysis excluded the non-bacterial magnesium-sulfate comparator (CMg) and included four PGPR strains, the uninoculated control, 200 plant-level observations, and 80 replication-level difference-in-differences (DiD) profiles. Nine nonredundant physiological traits were direction-aligned and standardized using the 2021 development season and aggregated with equal weights; all parameters were then applied unchanged to the 2022 holdout season. Block-adjusted MANOVA confirmed a joint inoculation variant × moisture interaction (Pillai’s trace = 0.533, F(36,664) = 2.835, p < 0.001). Block-restricted PERMANOVA detected a small multivariate strain effect (pseudo-F = 0.995, R² = 0.0378, p = 0.0289), whereas PERMDISP was nonsignificant (p = 0.273). In 2021, DLGB 2 obtained the highest PDMI (0.160) and had a 66.3% bootstrap probability of rank 1 and an 88.3% probability of inclusion in the top two. In the 2022 holdout, AJ 1.2 ranked first; cross-season rank agreement was positive but uncertain (Spearman’s ρ = 0.60, p = 0.40). The best individual trait, water-use efficiency, showed greater within-season rank stability than PDMI (P(rank 1) = 0.998), demonstrating that the composite did not universally outperform single measurements. PDMI was not significantly associated with holdout yield mitigation (R² = 0.0458; block-clustered p = 0.127; within-block permutation p = 0.341). PDMI should, therefore, be interpreted as a transparent integrative descriptor of coordinated physiological response rather than a definitive classifier, a universally superior screening metric, or a standalone yield predictor. Full article

Sweet basil (Ocimum basilicum L.) is a popular aromatic and medicinal crop cultivated globally. While its essential oils possess inherent antimicrobial properties, the plant remains highly susceptible to various pathogens. This study investigated the impact of a beneficial synthetic microbial community (SynCom)—composed of eight strains with proven antimicrobial and plant growth-promoting activities—on basil growth, ecophysiology, and metabolic profile in an aeroponic system. Although SynCom inoculation significantly enhanced photochemical efficiency, it did not yield significant gains in total biomass. Instead, inoculated plants exhibited a strategic reallocation of resources toward structural and chemical defenses. This physiological shift was physically manifested as denser plant canopies and lower specific leaf area (SLA). Untargeted metabolomic profiling identified 167 significantly altered metabolites. Notably, SynCom inoculation increased abscisic acid (ABA) turnover and redirected tryptophan metabolism from growth-promoting auxins to defense-related indoles and kynurenine derivatives. Furthermore, inoculation enriched the leaves with essential amino acids and a diverse array of protective secondary metabolites, including phenylpropanoids, flavonoids, and terpenoids. These findings demonstrate that specialized microbial inoculants can induce a transition toward fortified phenotypes and likely enhance plant resilience, even in the absence of traditional biomass gains. Full article

Salinity stress is one of the major stressors that limits yield potential in field crops. Salinity-led imbalances in ionic and water potential, as well as oxidative damage, impair photosynthesis. Plant-growth-promoting rhizobacteria (PGPRs) have been demonstrated to mitigate salinity-stress-induced damage through various mechanisms such as biofilm and exopolysaccharide production, modulation of plant root architecture or molecular signaling involving modulation of sodium/potassium efflux transporters. PGPRs are known to induce biosynthesis and signaling of various phytohormones in plants. PGPR-derived phytohormones can in turn regulate molecular signaling involved in maintaining ion fluxes, preventing salinity-induced senescence, and reinforcing plant root architecture, thereby maintaining plant growth and development under saline conditions. In this review, we provide comprehensive advances on how PGPRs modulate and integrate biosynthesis and/or signaling of various phytohormones, such as auxins, cytokinins, gibberellin, ethylene, abscisic acid, salicylic acid, jasmonates, brassinosteroids and strigolactones, to reshape plant architecture, physiological and biochemical responses in plants under salinity. We integrate molecular evidence with morpho-physiological studies and propose a phytohormone-centric framework to select strains that optimize growth, ion homeostasis and plant stress resilience under salinity. Full article

Botanical gardens are highly heterogeneous plant systems characterized by high taxonomic diversity, with numerous plant taxa represented within confined areas, and complex ecological interactions that create unique challenges for pest management. Conventional IPM strategies, designed for simplified agroecosystems, often fail to address complex pest pressures in curated environments. Microbial biostimulants have emerged as promising components of sustainable IPM strategies by enhancing plant defense responses, improving stress resilience, and reducing reliance on chemical inputs. This review synthesizes current knowledge on microbial biostimulants, including plant growth-promoting rhizobacteria, arbuscular mycorrhizal fungi and endophytic microorganisms, in modulating plant defense against insect herbivores. These beneficial microbes enhance plant resistance through multiple mechanisms. They activate induced systemic resistance and modulate key phytohormones, including jasmonic acid, salicylic acid, and ethylene. Additionally, they regulate calcium-dependent and reactive oxygen species-mediated defenses. Microbially induced changes in plant secondary metabolites and volatile organic compounds further influence herbivore behavior and trophic interactions. Emphasis is placed on integrating microbial biostimulants into IPM frameworks tailored to botanical gardens. This highlights compatibility with biological control agents and reduced reliance on synthetic pesticides. Despite promising advances, challenges remain, including context-dependent efficacy, host specificity and limited long-term validation. Overall, microbial biostimulants offer a promising tool for enhancing IPM in biodiversity-rich botanical gardens, although further long-term validation is needed to fully assess their sustainability and effectiveness. Full article

The degradation of Calcisols in the arid regions of Central Asia constrains sustainable agricultural production because of low organic matter content, poor aggregate stability, nutrient limitations, and increasing climatic stress. This study evaluated a rhizosphere engineering approach based on the native plant growth-promoting bacterium Pseudomonas veronii Ps-S/Sh-1503/2022 for the rehabilitation of degraded Calcisols. Four-year field experiments (2022–2025) using Sorghum bicolor assessed plant growth, rhizosphere microbial indicators, physiological responses, pathogen suppression, crop productivity, and implementation feasibility through economic and environmental assessments. Inoculation with P. veronii increased root depth by 45%, improved aboveground biomass, increased the ratio of culturable bacteria to Fusarium spp. from 6.1 to 10.3, and reduced Fusarium abundance by 29.4%. Structural equation modeling suggested that trophic support (42.1%), aggregate stabilization (27.4%), biocontrol (23.3%), and defense-related responses (7.2%) were the principal pathways associated with soil rehabilitation. Economic assessment indicated that the combined inoculation and mineral fertilization treatment provided the highest profitability, while environmental assessment estimated potential reductions in mineral fertilizer use and greenhouse gas emissions. These findings suggest that rhizosphere engineering using a native P. veronii strain represents a promising, economically viable, and climate-smart approach for improving the biological functioning of degraded Calcisols and supporting sustainable agricultural production. Full article

Spent mushroom substrate (SMS) is a major agricultural byproduct whose complex lignocellulosic matrix hinders direct reuse and poses environmental risks when stockpiled. This study evaluated whether pretreatment with plant growth-promoting rhizobacteria (PGPR) could enhance SMS as a soil amendment for blueberry cultivation. Two PGPR-treated SMS formulations, along with raw SMS and a blank control, were applied to blueberry seedlings in a 10-month greenhouse experiment. Plant height, rhizosphere soil nutrients, enzyme activities, lignocellulose fractions, and the microbial communities were monitored over three growth phases and four sampling points. PGPR-treated SMS significantly increased blueberry height gain during the fast-growing phase (June–September) and sustained elevated levels of organic carbon, nitrogen, phosphorus, and potassium throughout the experiment. Activities of cellulase, xylanase, laccase, peroxidase, protease, and lipase were markedly enhanced, accompanied by reduced lignin and cellulose contents and persistently high glucose availability. The amendments reshaped bacterial and fungal communities, enriching Bacillota, Acidobacteriota, Acidibacter, and Hyphomicrobium, and increasing alpha diversity, with clear structural separation from controls in principal coordinate analysis. Correlation and principal component analyses linked improved plant growth to nutrient availability, enzyme stimulation, and specific microbial taxa. These findings indicate that PGPR-treated SMS acts as a multifunctional amendment that promotes lignocellulose degradation, sustains soil fertility, and restructures the rhizosphere microbiome, offering a sustainable recycling strategy for horticultural production. Full article

Partial replacement of chemical fertilizers, particularly nitrogen fertilizers, with biological fertilizers is considered an effective strategy for reducing the negative environmental impacts associated with excessive fertilizer use. This study aimed to optimize N use through the application of bacterial-based biofertilizer, specifically plant growth-promoting rhizobacteria (PGPR), in different maize cultivars under semi-arid conditions. A randomized complete block design (RCBD) arranged in a split-plot arrangement was used, with the three hybrids (Shahkar, Bumbus and DK 7024) assigned to the main plots and different N treatments allocated to sub-plots. The field experiment was conducted during two consecutive spring seasons (Feb to June 2024 and 2025). The N treatments were defined as follows: control, 100% recommended N (200 kg/ha), 100% N with Pseudomonas stutzeri, 100% N with Bacillus subtilis, 100% N with Enterobacter sp., 50% N with Pseudomonas stutzeri, 50% N with Bacillus subtilis, 50% N with Enterobacter sp., 100% Pseudomonas stutzeri, 100% Bacillus subtilis, and 100% Enterobacter sp. The N treatments included synthetic fertilizer alone at the 100% recommended N rate and a combination of 100%, 50% and 0% of recommended levels with three N-fixing bacterial strains. Among the hybrids, DK 7024 exhibited the highest 1000-grain weight (349 g and 362.5 g), grain yield (6756 and 6971 kg ha⁻¹) and total dry matter (17,500 and 18,368 kg ha⁻¹) in 2024 and 2025, respectively. Among N levels, maximum 1000-grain weight, grain yield and total dry matter were noticed in 100% N with Enterobacter sp.: 402 g, 8446 kg ha⁻¹ and 21,656 kg ha⁻¹ in 2024 and 421 g, 8684 kg ha⁻¹ and 22,237 kg ha⁻¹ in 2025. Nitrogen application increased grain yield and total dry matter production; however, the treatment combined with 100% recommended synthetic N fertilizer with biofertilizer (Enterobacter sp.) showed superior performance compared with 100% N applied through only the synthetic fertilizer. The interaction between maize hybrids and N levels was statistically non-significant, suggesting that 100% N plus biofertilizers could be an effective strategy for achieving higher yields across different maize cultivars. Additionally, the beneficial effects of PGPR may contribute to sustainable agricultural practices. Further research is recommended to evaluate strategies involving reduced-N inputs combined with biological fertilizer, including the application of 100% N with biofertilizer. The present study suggests that N application in combination with biofertilizers has the potential to improve crop growth while promoting sustainable crop production. Full article

Lingonberry (Vaccinium vitis-idaea L.) has a weak root system and limited nutrient acquisition capacity. Plant growth-promoting rhizobacteria (PGPR) can promote plant growth by regulating rhizosphere nutrient cycling and host metabolism, but the underlying mechanisms in Ericaceae remain unclear. In this study, the strain Microbacterium sp. Y107 was isolated from the rhizosphere of lingonberry. Using growth-promoting assays (with 9 independent biological replicates, each consisting of 3 plants per bottle as the experimental unit, an inoculum density of OD₆₀₀ = 1.0, a cultivation period of 60 days, and whole-plant harvesting), GC–MS-based metabolite analysis, axenic coculture, analyses of the rhizosphere environment and gene expression, transcriptome sequencing (3 biological replicates per treatment), and qRT–PCR validation, we systematically evaluated the effects of strain Y107 on lingonberry growth, rhizosphere conditions, and host gene expression. CK (control) plants were defined as those inoculated with sterile LB liquid medium. Pearson correlation analysis was also used to assess the relationships among plant growth, soil traits, and physiological indices. Compared with the CK treatment, strain Y107 significantly promoted lingonberry growth (p < 0.05), increasing the fresh weight of the roots by 157.65% and the whole-plant fresh weight by 33.85%, respectively, and increasing peroxidase (POD) activity by 61.11%, while reducing the contents of reducing sugars and proline. Strain Y107 stably colonized the lingonberry root surface and formed biofilms. Y107 treatment resulted in detectable levels of soil microbial biomass carbon and nitrogen, indicating successful microbial colonization. The ammonium nitrogen content significantly increased, increasing nitrogen availability and promoting root nutrient uptake. Transcriptome analysis revealed that the expression of genes enriched in photosynthesis-related pathways, as well as those involved in carbon and nitrogen metabolism and redox regulation, was altered in strain Y107, which upregulated key photosynthesis-related genes such as psbP and ndhU and significantly enriched the cytosolic ribosomal large subunit gene set in a negative direction. Correlation analysis further revealed that strain Y107 optimized the association between lingonberry growth and soil nutrients. Overall, strain Y107 promoted lingonberry growth through stable colonization, enhanced nutrient cycling, promoted lingonberry growth, and altered the expression patterns of genes involved in photosynthesis-related pathways. Full article