Search Results (536)

Salinity stress severely constrains plant growth and ecosystem functioning in arid and semi-arid regions, and plant growth-promoting rhizobacteria (PGPR) have been increasingly applied to enhance plant salt tolerance. Hoswever, it remains unclear whether different PGPR inoculation strategies confer salt resistance through similar or distinct physiological pathways, particularly in perennial halophytes adapted to saline environments. In this study, a field experiment was conducted to evaluate the effects of single- and multi-strain PGPR inoculation on the growth performance, physiological responses, and stress regulation of Atriplex canescens under saline conditions. Plant biomass allocation, photosynthetic traits, osmotic adjustment substances, antioxidant enzyme activities, and comprehensive stress tolerance indices were systematically assessed. The results showed that PGPR inoculation significantly improved plant growth and stress tolerance; however, the magnitude and underlying mechanisms varied across inoculation strategies. Single-strain inoculation predominantly enhanced root development and antioxidant regulation, whereas multi-strain inoculation tended to promote aboveground growth and photosynthetic performance. In contrast, certain strain combinations did not produce additive benefits, suggesting potential incompatibility among microbial consortia under salt stress. Multivariate analyses further indicated that improvements in stress tolerance were more closely associated with coordinated physiological regulation than with biomass accumulation alone. Overall, our findings demonstrate that PGPR-mediated salt tolerance in A. canescens is strategy-dependent and involves distinct resource allocation and stress-defense pathways. These results highlight the importance of considering inoculation strategies and functional compatibility when applying PGPR to improve plant performance in saline ecosystems. Full article

Salinity stress severely limits crop productivity worldwide. While plant growth-promoting rhizobacteria (PGPR) are known to alleviate abiotic stress, the specific mechanisms mediated by their volatile organic compounds (VOCs) remain largely elusive. In this study, an in vitro split-plate system was used to investigate the effects of VOCs emitted by Bacillus velezensis SQR9 on Arabidopsis thaliana seedlings under salt stress. Exposure to SQR9 VOCs significantly enhanced Arabidopsis salt tolerance, evidenced by increased biomass and root growth. Mechanistically, SQR9 VOCs mitigated salt-induced damage by increasing chlorophyll content, modulating osmolytes, and reducing malondialdehyde (MDA) levels. SQR9 VOCs alleviated oxidative stress by decreasing ROS (H₂O₂, O₂⁻) accumulation and enhancing antioxidant enzyme (SOD, CAT, POD) activities. Furthermore, SQR9 VOCs maintained ion homeostasis by significantly reducing leaf Na⁺ accumulation, maintaining a high K⁺/Na⁺ ratio, and upregulating key ion transporter genes. Analysis of the headspace from SQR9 cultured on MSgg medium identified 2,3-butanediol (2,3-BD) as a major active VOC. Exogenous application of 2,3-BD successfully mimicked the growth-promoting and salt-tolerance-enhancing effects of SQR9. Our findings demonstrate that SQR9 VOCs, particularly 2,3-BD, systemically prime Arabidopsis for salt tolerance by co-activating the antioxidant defense system and the SOS ion homeostasis pathway. Full article

This systematic review critically evaluates and synthesizes current evidence on the efficacy of biostimulants in enhancing soybean seed yield and quality. A comprehensive literature search was conducted following the PRISMA approach using the Web of Science (WoS) database, focusing on peer-reviewed studies from 2014 to 2025 reporting on the effects of biostimulants applied alone or in combination with other agro-inputs on soybean performance. Over 500 publications were retrieved from the database, of which 72 were included in this review. Extracted data were used to calculate changes in yield (kg ha⁻¹), percentage yield increase (%), oil content (%), and protein concentration (%). Our synthesis demonstrated that the sole application of biostimulants, including seaweed extracts, humic acids, amino acids, and beneficial microbes (Bradyrhizobium, PGPR, AMF), consistently enhanced soybean yield by 4% to 65%, while their interaction with other agro-inputs was shown to be capable of increasing yield by more than 150% under abiotic stress conditions, indicating strong synergistic effects. These improvements are mediated through various physiological mechanisms such as enhanced nutrient uptake, improved root growth, increased photosynthetic efficiency, and elevated stress tolerance. Furthermore, biostimulant application positively affects seed quality, increasing oil and protein content by 0.4–5.5% and 0.5–7.3%, respectively, by optimizing source–sink relationships and metabolic pathways. Overall, the greatest benefits are frequently observed through synergistic combinations of biostimulants with one another or with reduced rates of mineral fertilizers, highlighting a promising pathway toward sustainable crop intensification in soybean systems. Full article

Continuous monoculture of Panax notoginseng leads to severe replant disease, yet the mechanisms by which root exudates mediate rhizosphere microbiome assembly and pathogen enrichment remain poorly understood. Here, we demonstrate that long-term root exudate accumulation acts as an ecological filter, driving the fungal community toward a phylogenetically impoverished, pathogen-dominated state. Specifically, exudates enriched the soil-borne pathogen Fusarium while reducing the abundance of potentially antagonistic fungi. In contrast, bacterial communities exhibited higher resilience, with exudates selectively enriching oligotrophic taxa such as Terrimonas and MND1, but suppressing nitrifying bacteria (e.g., Nitrospira) and plant-growth-promoting rhizobacteria (PGPR). Microbial functional profiling revealed a shift in nitrogen cycling, characterized by suppressed nitrification and enhanced nitrate reduction. Crucially, co-occurrence network analysis identified bacterial taxa strongly negatively correlated with Fusarium, providing a synthetic community blueprint for biocontrol strategies. Our study establishes a mechanistic link between root exudate accumulation and negative plant–soil feedback in monoculture systems, highlighting microbiome reprogramming as a key driver of replant disease. These insights offer novel avenues for manipulating rhizosphere microbiomes to sustain crop productivity in intensive agricultural systems. Full article

Plants are naturally exposed to various biotic stresses, including pathogen attacks and insect herbivory, which activate distinct signaling pathways as part of their defense responses. Inoculation with beneficial microorganisms, such as plant growth-promoting rhizobacteria (PGPR), can trigger induced systemic resistance (ISR) in plants, a defense response that resembles the one activated by herbivore attack in terms of signaling pathways and physiological effects. However, these interactions have typically been studied independently, limiting our understanding of their combined effects. In this study, we examined the effects of aphid (Acyrthosiphon pisum) herbivory on Ocimum basilicum plants and assessed how these responses are modulated when the plants are inoculated with the PGPR strain Bacillus amyloliquefaciens GB03, with a particular focus on biochemical and structural defense mechanisms. Aphid herbivory significantly increased total essential oil (EO) content and volatile organic compound (VOC) emission and induced a greater density of glandular trichomes while also modifying the phytohormone profile. In contrast, total phenolic content remained unchanged. When aphid herbivory occurred on GB03-inoculated plants, the effects on defense-related parameters became more pronounced. EO and eugenol contents were further increased compared with inoculated controls, jasmonates remained comparable to levels induced by either factor alone, and SA levels nearly doubled relative to aphid-infested plants. Feeding assays revealed that aphids preferred inoculated plants over controls, a response that may be explained by the increased emission of eugenol in inoculated basil. These results demonstrate that GB03 inoculation modifies several defenses-related responses in O. basilicum upon aphid herbivory, including by hormonal signaling, specialized metabolites accumulation, and structural barriers such as glandular trichomes. These findings suggest that PGPR may contribute to modulating plant responses to herbivory under certain conditions, highlighting their context-dependent influence within plant–microbe–insect interactions. Full article

Background: The Songnen Plain in China contains soda saline–alkaline soil, wherein salinity and alkalinity severely constrain crop productivity. Alfalfa (Medicago sativa L.) is a forage legume that has adapted to moderate saline–alkaline conditions, but how its rhizosphere microbial community facilitated this adaptation remains unclear. Methods: Using 16S rRNA gene sequencing, we compared alfalfa rhizosphere bacteria in saline–alkaline soil (AS) and control soil. Bacteria isolated from AS were screened for plant growth-promoting traits, with the most effective strains validated in pot experiments involving 50 mM NaHCO₃. Results: Compared with the control soil bacterial community, the AS bacterial community was significantly enriched with Methylomirabilota and unclassified bacteria (phylum level), with the genus RB41 identified as the most discriminative biomarker. Gene functions predicted using PICRUSt2 reflected the responsiveness of this community to environmental stressors. Inoculations with Pseudomonas laurentiana strain M73 and Stenotrophomonas maltophilia strain M81, which were isolated from AS, significantly improved alfalfa growth and health under NaHCO₃ stress. Conclusions: Saline–alkaline conditions in the Songnen Plain reshape the alfalfa rhizosphere bacterial community, enriching for specific taxa and potentially enhancing microbial functions associated with stress resistance. Strains M73 and M81 can effectively promote stress tolerance, making them useful microbial resources for improving soil conditions. Full article

Drought stress, exacerbated by climate change, is a serious threat to global food security. This review examines the synergistic potential of plant growth-promoting rhizobacteria (PGPR) and biochar as a sustainable strategy for enhancing crop drought resilience. Biochar’s porous structure creates a protective “charosphere” microhabitat, enhancing PGPR colonization and survival. This partnership, in turn, induces multifaceted plant responses through: (1) the modulation of key phytohormones, including abscisic acid (ABA), ethylene (via 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity), and auxins; (2) improved nutrient solubilization and uptake; and (3) the activation of robust antioxidant defense systems. These physiological benefits are orchestrated by a profound reprogramming of the plant transcriptome, which shifts the plant’s expression profile from a stressed to a resilient state by upregulating key genes (e.g., Dehydration-Responsive Element-Binding protein (DREB), Light-Harvesting Chlorophyll B-binding protein (LHCB), Plasma membrane Intrinsic Proteins (PIPs)) and downregulating stress-senescence markers. To realize a climate-resilient farming future, research must be strategically directed toward customizing biochar–PGPR combinations, validating their long-term performance in agronomic environments, and uncovering the molecular bases of their action. Full article

The individual application of salt-tolerant plant growth-promoting rhizobacteria (ST-PGPR) or organic amendments exhibits certain limitations in remediating saline-alkali soils. This study developed a co-application treatment by combining a functionally complementary ST-PGPR consortium (Bacillus velezensis and Bacillus marisflavi) with optimized organic amendments (biochar at 22.5 t·ha⁻¹ and sheep-manure organic fertilizer at 7.5 t·ha⁻¹) to enhance soil quality and wheat growth. Compared with the control, the combination of the ST-PGPR consortium with organic amendments significantly reduced soil electrical conductivity by 52.69%. while soil organic matter, alkaline nitrogen, available phosphorus, and available potassium increased by 54.37%, 7.68%, 11.85%, and 39.57%, respectively (p < 0.05). The activities of sucrase, urease, and catalase also increased by 147.69%, 28.56%, and 30.26%, respectively (p < 0.05). Furthermore, the combined treatment significantly promoted wheat growth, increasing plant height, root length, and fresh weight by 12.11%, 26.60%, and 35.00%, respectively (p < 0.05), while alleviating osmotic and oxidative stress. β-diversity analysis revealed distinct microbial community compositions across treatments, and microbial composition indicated that Actinobacteriota and Starmerella were enriched under the co-application. Additionally, the co-application significantly enhanced the complexity and interconnectivity of the bacterial network, while reducing the stability of the fungal network. Partial least squares path and random forest models identified soil chemical properties as the key factors driving wheat growth. This synergistic system presents a promising and sustainable strategy for remediating saline-alkali soils and enhancing crop productivity. Full article

Soil salinity imposes a critical constraint on plant productivity, highlighting the need for sustainable biological strategies to enhance stress tolerance. This study assessed the effects of volatile organic compounds (VOCs) emitted by ten plant-growth-promoting rhizobacteria (PGPR) isolated from the rhizosphere of Euphorbia antisyphilitica on the growth of Arabidopsis thaliana seedlings exposed to 0, 50, and 100 mM NaCl. A divided Petri dish system was used to quantify biomass, root architecture, proline accumulation, sodium content, and chlorophyll concentration. Three strains—Siccibacter colletis CASEcto12, Enterobacter quasihormaechei NFbEcto18, and Bacillus wiedmannii NFbEndo12—significantly enhanced seedling development under saline and non-saline conditions (p ≤ 0.05). At 50 mM NaCl, S. colletis CASEcto12 increased primary root length from 40.25 to 64.81 mm and fresh weight from 45.05 to 133.33 mg, while E. quasihormaechei NFbEcto18 elevated lateral root number from 10 to 24, compared to the uninoculated control. Under 100 mM NaCl, E. quasihormaechei NFbEcto18 increased proline accumulation (0.564–1.378 mmol g⁻¹ FW) and reduced Na⁺ content (0.146–0.084 mmol g⁻¹ FW), indicating improved osmotic and ionic regulation. VOC profiling using SPME-GC-MS revealed aldehydes, ketones, and alcohols as predominant classes. Overall, these findings demonstrate the potential of candelilla-associated PGPR VOCs as promising biostimulants for enhancing plant performance in salt-affected soils. Full article

The production and productivity of cereal crops, which form the foundation of global food security, are increasingly threatened by unstable water regimes and recurring droughts linked to climate change. Fortunately, a wide diversity of cereal crops is endowed with natural resilience to drought and heat stress, enabling them to survive under conditions that are critical for other plants. Understanding the key morphological, genetic, physiological, biochemical, and ecological mechanisms—and their interactions—is crucial for unraveling the processes involved in drought tolerance in these species. A comprehensive study of cereal crops, their variability, and their ability to survive and thrive under arid conditions will unlock new opportunities for breeding drought-resistant agricultural varieties. This review highlights the role of root system architecture (RSA) and gravitropic mechanisms (e.g., EGT1, DRO1), the integration of phytohormonal crosstalk, the potential of wild relatives and genome editing, and the emerging role of plant growth-promoting rhizobacteria (PGPR) in enhancing drought resilience. We propose a novel synthesizing concept focused on overcoming the fundamental yield-survival trade-off by framing drought resilience through the lens of optimizing three interconnected functional modules: water budget architecture, metabolic homeostasis, and integrative signaling networks. The central advance of this framework is its systems-level perspective that redefines these well-studied components as dynamically interacting, tunable modules, providing a practical blueprint for designing crop ideotypes that break the yield-survival trade-off. Full article

Modern fruit crop production increasingly seeks sustainable strategies to enhance growth, yield, and fruit quality while minimizing environmental impacts. Plant biostimulants—naturally derived substances or beneficial microorganisms, such as seaweed and plant extracts, Plant-Growth-Promoting Rhizobacteria (PGPR), humic substances, protein hydrolysates, and Si—emerge as promising tools to achieve these goals by stimulating key physiological and biochemical processes. They can improve nutrient uptake and efficiency, modulate hormonal and metabolic pathways, and enhance the activity of enzymatic and non-enzymatic antioxidants, leading to improved plant vitality and fruit quality. Biostimulants also influence rhizosphere microbial communities and soil health, promoting nutrient cycling, beneficial microbial diversity, and soil structure. This review evaluates the application of biostimulants in fruit crops and their effects on growth, physiology, productivity, fruit quality, both chemical and nutritional composition and physical parameters. Challenges related to variability in efficacy, formulation standardization, and crop-specific responses are discussed, alongside future perspectives on integrating biostimulants into sustainable orchard management. Overall, biostimulants represent multifunctional tools that support both productivity and ecological sustainability in modern fruit production systems. Full article

Excessive fertilizer use poses environmental risks in the long term. Thus, plant growth-promoting rhizobacteria (PGPR) have been proposed as a complementary approach to reduce fertilizer use and prevent nutrient stress. Moreover, PGPR’s efficacy in sandy soil for sweet potato production in Northeast Thailand has not yet been reported. This study tested the hypothesis that PGPR inoculation could reduce fertilizer dependency while maintaining yield in nutrient-poor sandy soils. In this research, a field study was conducted from 2023 to 2024 in Chonnabot District, Khon Kaen, Thailand, to evaluate the effects of Azospirillum brasilense, Azotobacter vinelandii, Beijerinckia mobilis, and inorganic fertilizer on the Okinawan Orange and Carrot native sweet potato varieties. Treatments followed a factorial randomized complete block design with two factors, PGPR inoculation and fertilizer level (0%, 25%, 50%, 75%, and 100%), and were replicated three times. The results showed that PGPR dipping had no statistically detectable effect on sweet potato growth and yield (p > 0.05). However, a notable finding was that PGPR significantly increased the protein and fiber content of tubers (p < 0.01) while reducing carbohydrate content, which may have implications for the taste and the nutritional quality of sweet potatoes. In addition, the application of inorganic fertilizer had a significant effect on yield. The Carrot native variety achieved the highest yield (13,481.00 kg ha⁻¹) with 75% fertilizer, while the Okinawan Orange variety attained the highest yield (8866.00 kg ha⁻¹) with 100% fertilizer. These data could be used to assist farmers in determining their fertilizer usage. Full article

Soil salinity is a serious abiotic stressor threatening global agriculture, currently affecting nearly 20% of irrigated land, with projections suggesting that almost 50% of cultivated areas may be impacted by 2050. Plant growth-promoting rhizobacteria (PGPR) and Silicon (Si) have been widely investigated for their individual roles in improving plant tolerance to salinity, yet their combined application—particularly using Si nanoparticles (SiNPs), remains underexplored. This review synthesizes current knowledge on PGPR, SiNPs, and their synergistic effects in mitigating salinity stress, with emphasis on physiological, biochemical, and molecular mechanisms. Special attention is given to Si-mediated regulation of stress-responsive genes (e.g., RD29B, DREB2b, RAB18, HKT1, WRKY TFs, CAT, POD) and PGPR-induced gene expression (e.g., GmST1, GmLAX3, NHX1, NRT2.2, GR), which are directly linked to ion homeostasis, osmolyte accumulation, and antioxidant activation. In addition, crop-specific case studies and emerging molecular insights are highlighted to demonstrate practical applications. Despite these promising findings, significant challenges remain, including the stability of nanoformulations, microbial compatibility, and the lack of field-scale validation under diverse agro-climatic conditions. This review highlights knowledge gaps and briefly outlines future directions for the integrated use of PGPR and SiNPs as sustainable strategies to enhance crop resilience under salinity stress. Full article

Cowpea Fusarium wilt (CFW) is a soilborne fungal disease caused by Fusarium oxysporum f. sp. tracheiphilum (Fot), leading to substantial yield losses globally. This study evaluates the biocontrol potential of Bacillus velezensis HAB-2 and develops a microbial combination for effective disease management. B. velezensis HAB-2 suppressed F. oxysporum f. sp. tracheiphilum AIQBFO93 growth by 69.8% in vitro and exhibited multiple plant growth-promoting traits. Pot experiments demonstrated that HAB-2 alone achieved a 47.62% control rate against CFW. Furthermore, two compatible plant growth-promoting rhizobacteria (PGPR), Pseudomonas hunanensis HD33 and Enterobacter soli HD42, were isolated from the rhizosphere soil of cowpea previously treated with HAB-2. These two strains were combined with HAB-2 at different concentrations in 15 microbial combinations. The combined application of the three strains provided more consistent disease control, with the optimal combination demonstrating a 15.15% higher control rate than HAB-2 alone. Compared to the untreated control, this combination significantly increased cowpea fresh weight, leaf area, and plant height by 10.60%, 8.04%, and 7.81%, respectively, and upregulated the expression of defense-related genes, indicating enhanced resistance. These results confirm that B. velezensis HAB-2 is an effective biocontrol agent against wilt disease, and its synergistic application with functionally complementary PGPR strains provides a viable strategy for sustainable crop disease management. Full article

A trial was conducted from 2017 to 2023 in a 0.2 ha irrigated vineyard located in a semiarid area of southeastern Spain, using field-grown young vines (0–6 years old) of Vitis vinifera L. cv. Monastrell grafted onto three rootstocks: 140Ru, 161-49C, and 110R. The main objective was to evaluate the effect of early co-inoculation in the field using commercial microbial inoculants containing arbuscular mycorrhizal fungi (AMF), plant growth-promoting rhizobacteria (PGPR), and a mycorrhizal helper bacterium (MHB) on young vine performance. We assessed the impact of microbial inoculation and its interaction with the rootstock on soil environment, plant water relations, leaf gas exchange, plant nutrition, growth, yield, and berry quality. Mycorrhizal colonization rates in root samples showed similar values in inoculated and non-inoculated vines across all of the rootstocks; however, inoculated vines grafted onto 140Ru showed significantly higher concentrations of total glomalin in the soil compared to their non-inoculated counterparts. Microbial inoculation altered the soil environment, leading to increased oxygen diffusion rate (161-49C), organic matter decomposition rate (140Ru), soil CO₂ flux (110R, 140Ru), and soil H₂O flux (110R) values in the rhizosphere of inoculated vines. Additionally, inoculated vines grafted onto 140Ru and 161-49C exhibited improved vegetative and reproductive development, enhancing productive water use efficiency (WUE_yield), whereas inoculated vines on 110R showed poorer soil–plant water relations, growth, yield, and WUE_yield compared to non-inoculated vines. Microbial inoculation also led to a significant decrease in must phenolic content, particularly in 140Ru, unlike 110R and 161-49C. These findings indicate that early microbial inoculation had a rootstock-dependent impact on the performance of young grapevines. Full article