Search Results (749)

As a globally popular crop, strawberry is highly susceptible to cold stress, which significantly limits its cultivation and yield. This review synthesizes current knowledge on the morphological, physiological, and molecular responses of strawberry plants to cold stress. Morphologically, cold stress induces chlorosis, necrosis, and growth retardation, while physiologically, it impairs photosynthesis and membrane integrity and triggers oxidative stress. At the molecular level, the cold acclimation process in plants is orchestrated by a sophisticated regulatory network centered on the ICE-CBF/DREB signaling pathway and incorporating transcription factors, epigenetic modifications, and non-coding RNAs. The accumulation of protective compounds like proline, anthocyanins, and antioxidants is a key metabolic adaptation. Finally, we discuss integrative management practices and future breeding strategies, including genetic engineering, marker-assisted selection, and the use of plant growth-promoting rhizobacteria to enhance cold tolerance. This comprehensive overview provides valuable insights for developing resilient strawberry varieties in the face of unpredictable climate events. Full article

Polyaspartic acid (PASP), a biodegradable and eco-friendly fertilizer synergist that shows potential to enhance nutrient use efficiency in agricultural systems, has its integrative role with rhizosphere microorganisms remain insufficiently explored. This study integrated outdoor pot experiments, soil biochemical analysis, and microbiome sequencing to investigate the effects of co-application of PASP and the plant growth-promoting rhizobacterium (PGPR) Enterobacter asburiae S13 on potato growth, with four treatments set up including blank control (CK), sole application of PASP (S0P1), sole inoculation of PGPR (S1P0), and co-application of PASP and PGPR (S1P1), and 25 pots per treatment as replicates. The results showed that, compared with the S0P1 treatment, the S1P1 treatment significantly increased plant height (9.59%), stem diameter (28.39%), root length (38.61%), as well as root and shoot biomass (21.26% and 25.17%, respectively) (ANOVA, Duncan’s test, p < 0.05). It also enhanced ammonium nitrogen (40.00%), nitrate nitrogen (57.70%), available potassium (47.56%), and urease activity in the rhizosphere soil (ANOVA, Duncan’s test, p < 0.05). 16S rRNA sequencing revealed that the S1P1 treatment enriched beneficial taxa such as Paucibacter and Massilia, while suppressing competitive genera such as Duganella and Pedobacter. Redundancy analysis (RDA) indicated that available potassium and ammonium nitrogen were the key factors shaping the microbial community structure. In conclusion, combining PASP with PGPR synergistically improves soil nutrient availability and reshapes the rhizosphere microbiome, resulting in enhanced potato growth, thus demonstrating its potential as a dual-function biostimulant for eco-efficient and sustainable potato production systems. 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

The secondary metabolite 2,4-diacetylphloroglucinol (2,4-DAPG), which is produced by Pseudomonas bacteria, is a potent antimicrobial agent with well-documented properties that suppress phytopathogens. However, its broader ecological impact on soil microbial communities is not understood. Through a combination of controlled microcosm and field trials, we have demonstrated that the effects of 2,4-DAPG are highly context-dependent. Laboratory exposure (10 mg kg⁻¹) altered the abundance of 8.53% of bacterial and 6.91% of fungal amplicon sequence variants, and simplified the bacterial co-occurrence networks (reduced number of nodes and links). In contrast, field conditions amplified bacterial sensitivity (the Shannon index decreased from 4.77 to 4.17, p < 0.05) but maintained fungal stability (Shannon index varied from 3.93 to 3.97, p > 0.05); these conditions affected a smaller proportion of fungal ASVs (4.23%). Taxonomic analysis revealed consistent suppression of fungi of the Mucoromycota (e.g., Mortierella) and context-dependent shifts in bacteria, with an enrichment of Bacillota (e.g., Bacillus, Paenibacillus) in the laboratory but not in the field. Enzymatic responses revealed a dose-dependent activation of the C-cycle, with up to 7.4-fold increases in the laboratory and up to a 10.5-fold increase in the field. P- and N- cycles showed more complex dynamics, with acid phosphatase activity increasing 3.8-fold in laboratory conditions and recovering from initial suppression to an increase of 144% in field conditions, while N-acetylglucosaminidase activity increased and L-leucine aminopeptidase decreased under laboratory conditions. Our results suggest that the response of microorganisms to 2,4-DAPG in natural soils is reduced, probably due to functional redundancy and pre-adaptation to abiotic stresses. This difference between laboratory and field studies warns against extrapolating data from controlled experiments to predict outcomes in agricultural ecosystems, and emphasizes the need for a context-specific evaluation of biocontrol agents. 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

With the development of microbial fertilizers, efforts have been made to enrich the strain resources of plant growth-promoting rhizobacteria (PGPR) in maize and to compare the growth-promoting effects of synthetic microbial communities (SynComs) with those of single strains. To achieve this, phenotypic measurements and RNA sequencing (RNA-seq) were performed on maize roots treated with SynComs and single-strain bacterial suspensions, aiming to investigate the regulatory influence of PGPR on differential gene expression and key metabolic pathways in maize roots. In this study, 59 PGPR strains were selected, representing genera including Bacillus, Pseudomonas, Burkholderia sp., Curtobacterium pusillum, Acidovorax, Sphingobium, Mitsuaria, Bacterium, Rhodanobacter, Variovorax, Ralstonia, Brevibacillus, Terrabacter, Flavobacterium, Comamonadaceae, Achromobacter, Paraburkholderia, and Massilia. Based on the growth-promoting effects observed in pot experiments, optimal bacterial strains were selected according to the principles of functional complementarity and functional superposition to construct the SynCom. The selected strains included Burkholderia sp. A2, Pseudomonas sp. C9, Curtobacterium pusillum E2, and Bacillus velezensis F3. The results demonstrated that individual strains exerted measurable growth-promoting effects on seedlings; however, the growth-promoting capability of the SynCom was significantly stronger than that of single strains. The synthetic microbial community ALL group markedly increased root length, shoot fresh weight, shoot dry weight, number of branches, and number of root tips in maize seedlings. RNA-seq analysis of maize roots treated with the SynCom (ALL group) was conducted in comparison with CK, A2, C9, E2, and F3 treatment groups. A total of 5245 differentially expressed genes (DEGs) were identified, of which only 133 were common across treatments. GO and KEGG analyses revealed that DEGs were enriched in multiple biological processes, including cellular amide biosynthetic and metabolic processes, flavonoid biosynthetic and metabolic processes, carbohydrate metabolism, amino acid metabolism, lipid metabolism, and translation. The majority of enriched pathways were associated with primary and secondary metabolism, indicating that these bacterial strains promote plant growth by modulating a wide range of metabolic pathways in plant cells. Overall, this study provides a molecular framework for understanding the mechanisms underlying the growth-promoting effects of SynComs on maize roots and offers valuable insights for future research aimed at identifying key regulatory genes. Full article

Alfalfa (Medicago sativa L.) is a crucial plant for saline and alkaline soil development, which is crucial for managing the salinization of global land resources. It can withstand saline and alkaline stress and can fix nitrogen. By secreting phytohormones, fixing nitrogen, and boosting antioxidant capacity, nitrogen–fixing bacteria, rhizobacteria, and other inter–root biotrophic bacteria encourage alfalfa development and reduce salinity stress. Alfalfa’s symbiotic association also encourages other plants to tolerate salinity and greatly boosts the amount of nitrogen in the soil. The mechanism by which inter–root growth–promoting bacteria mitigate saline and alkaline stress in alfalfa remains a prominent research focus. This paper reviews the current state of research on inter–root probiotic bacteria associated with alfalfa, utilizing literature mining to summarize the resource information of inter–root nitrogen–fixing bacteria found in saline–alkaline soils. We elucidate their nitrogen-fixing mechanisms and adaptive characteristics, explore their roles and potential applications in the improvement of saline–alkaline lands, and provide a theoretical foundation for the development of novel nitrogen–fixing bacterial fertilizers and restoration technologies for saline–alkaline environments. Full article

Smallholder farming plays a crucial role in global food security, contributing more than half of the world’s food supply. However, it is increasingly threatened by climate variability, declining soil fertility, and financial constraints, all of which suppress plant growth, reduce yields, and endanger livelihood stability. Addressing these challenges requires sustainable, eco-friendly alternatives to costly and environmentally damaging agrochemicals. Sorghum, a climate-resilient cereal, harbours a diverse microbiome that contributes significantly to its remarkable adaptability under adverse conditions. Harnessing the sorghum-associated microbiome, therefore, represents a promising, low-cost, and sustainable strategy to enhance sorghum productivity and resilience in smallholder farming systems. However, despite its potential, the adoption of microbiome-based technologies among smallholders remains limited due to a lack of local production units, poor government policies, knowledge gaps, and perceived risks. Although many studies report positive outcomes from microbiome-based interventions, translating this potential from controlled experiments to real-world field applications requires a critical evaluation of the efficacy, practicality, and limitations of microbial interventions. Furthermore, the outcomes of these studies are uneven, highly context-dependent, and often restricted to short-term or small-scale trials. This review, therefore, seeks to highlight current understanding of the sorghum microbiome, including its composition and the procedures for isolating and characterising beneficial microbes. It further evaluates the key challenges hindering adoption and proposes strategies to overcome them. Ultimately, this review advocates for integrating sorghum-associated microbiome technologies within integrated farming systems, underscoring their potential to enhance sustainable crop production, strengthen smallholder resilience, and contribute to the global sustainable development goals. Full article

Biochar can act as a carrier and a soil carbon source for rapid colonization by plant growth-promoting rhizobacteria (PGPR). However, the effects of a combined application of biochar and PGPR on soil physicochemical properties, humus components, and their stability in the rhizosphere around fruit mulberry seedlings remain unclear. A pot experiment using 1-year-old fruit mulberry seedlings with five treatments (control (CK), salt stress (SS), salt stress + Bacillus fexus (SS+P), salt stress + biochar (SS+B), and salt stress + B. fexus + biochar (SS+P+B)) was conducted to analyze the variations in soil physicochemical properties and humic acid (HA), fulvic acid (FA), and humin (HM) contents in the soil when planting fruit mulberry seedlings. The results indicated that the SS treatment significantly reduced total soil porosity, non-capillary porosity, water stable macro-aggregates content, available potassium content, and pH value compared to CK, but increased the soil bulk density, capillary porosity, and available phosphorus content. The SS+P+B treatment significantly increased soil total porosity, non-capillary porosity, pH value, electrical conductivity, the water stable macro-aggregates, organic matter, HA and HM contents, the HA/FA and HA/HE (humus-extractable) ratios, and the activities of catalase and urease. It significantly increased the water stable macro-aggregates and the HA/HE ratio by 27.83% and 25.00%, respectively. However, it significantly decreased soil bulk density and capillary porosity by 9.93% and 20.64%, respectively, compared to the SS treatment. The results suggest that the simultaneous addition of biochar and B. fexus under salt-stress conditions improves the soil physicochemical properties and increases the humus components content and stability, which is of great significance for improving the soil quality of saline–alkali land and enhancing the productivity of fruit mulberry. Full article

Bacillus subtilis is applied as a biofertilizer, biocontrol agent, and probiotic in agriculture, and is also used for industrial synthesis of proteins and peptides. These applications can be combined by using B. subtilis to synthesize plant health-promoting peptides in culture or to deliver them to roots via seed treatments. To facilitate the use of B. subtilis as a cell factory, we tested different media, temperatures, and growth phases to optimize ectopic expression of a Plant Elicitor Peptide from soybean (GmPEP3) that enhances seedling growth. Our results indicate that temperature, culture media, and growth phase have interactive effects, and that 30 °C and 2x YT media can enhance ectopic expression per cell compared to 37 °C or LB media in log phase bacteria. We also identified tradeoffs between cell growth and ectopic expression levels per cell, with the log phase favoring high expression per cell but the stationary phase yielding higher cell numbers and consequently higher expression levels per unit of growth media. In addition, to facilitate B. subtilis seed treatments, we compared retention of spores versus vegetative cells with and without carboxymethylcellulose (CMC) to improve the viability of B. subtilis seed treatments. Our results indicated that retention of viable bacteria on B. subtilis-treated seeds could be increased by ~40% by using the adhesive polymer CMC, and shelf life could be extended from 24 h to at least 3 months by using endospores rather than vegetative cells. For B. subtilis expressing GmPEP3, endospores also had comparable plant-growth-promoting activity as vegetative cells. This establishes the bioactivity of spores and illustrates the potential benefits of using B. subtilis to deliver heterologous peptides. These results provide valuable insights for deploying B. subtilis for crop health. Full article

Soil salinity and water scarcity are major challenges limiting agricultural productivity in arid and semi-arid regions. Quinoa (a climate-resilient crop) offers potential for sustainable food production under these harsh conditions; however, its growth and yield are often constrained by salt and water stress. This study evaluated the role of plant-growth-promoting rhizobacteria (PGPR) in enhancing Chenopodium quinoa Willd performance under deficit irrigation (DI) with saline water. A greenhouse pot experiment was conducted with four irrigation levels (40%, 60%, 80%, and 100% of the growth water requirement, GWR) and two water qualities (fresh water, EC = 0.8 dS m⁻¹; and saline water, EC = 6.0 dS m⁻¹), each tested with and without PGPR inoculation. The results showed that PGPR application significantly (p < 0.05) improved quinoa tolerance to salinity, leading to higher biomass, yield, and crop water productivity (CWP) under saline irrigation. Yield reductions were most severe at 40% GWR (53.9% and 82.6% under saline and fresh water, respectively), but PGPR inoculation mitigated yield losses, with increases of 83.3% and 130.8% under 40% and 100% GWR saline irrigation, respectively. Notably, PGPR did not show a clear effect with freshwater irrigation. In addition, inoculated plants exhibited improved nutrient uptake and reduced heavy metal accumulation. Overall, PGPR demonstrated strong potential to enhance salinity resilience and water-use efficiency in quinoa. Future studies should extend these findings under field conditions and investigate the long-term impacts of PGPR on sustainable crop production in saline- and water-limited environments. Full article

Global concerns about resource depletion, climate change, and nutrient pollution in aquatic systems are compelling a transition towards zero-waste industries. With the skyrocketing carbon footprint of the modern fertiliser industry, sustainable options are highly sought after. Anaerobic digestion of organic waste to generate renewable biogas and fertiliser production from the residual nutrient-rich digestate are promising nutrient recovery and recycling avenues. This review explores the potential use of anaerobic digestate to develop value-added agronomic products, focusing on the quality and safety parameters pivotal to its fertiliser value. A comprehensive review of conventional and cutting-edge technologies available for digestate processing into organic/organo-mineral fertilisers has been conducted, highlighting emerging sustainable approaches. Specifically, this review unravels novel aspects of enhancing digestate quality with biostimulants such as plant growth-promoting rhizobacteria, humic substances and biochar for biofertiliser/slow-release fertiliser production. Additionally, methods and guidelines to assess and address environmental impacts by digestate application on croplands and challenges in the commercialisation of digestate-based fertilisers were analysed. This review also underscores the importance of valorising anaerobic digestate as a fertiliser in implementing a circular bioeconomy within the agroindustry. Full article

The excessive use of irrigation water and fertilizers in agriculture raises serious environmental concerns, emphasizing the need for more sustainable practices. Screening genotypes with reduced nutrient and water requirements, combined with favorable responses to plant growth-promoting rhizobacteria (PGPR), offers a promising strategy for developing more sustainable farming systems. Seven sweet pepper genotypes (Capsicum annuum L.) were evaluated under six treatments, involving two fertilization levels (100% and 50% standard dose), two irrigation regimes (100% and 75% full irrigation), and PGPR inoculation applied under reduced fertilization. Yield, fruit weight, rhizosphere enzymatic activities, and soluble sugars in green and red fruits were evaluated. The genotype effect contributed significantly to all traits. Combined reductions in fertilizer and irrigation decreased average yield by 21.7%, while PGPR did not fully compensate for these losses. Alkaline phosphomonoesterase activity increased by 22.9% under low fertilization, whereas averaged catalase and dehydrogenase remained relatively stable regardless of PGPR. In green fruits, PGPR inoculation under combined stress conditions increased glucose and fructose concentrations by 11.6% and 13.9%, respectively, compared to uninoculated stressed plants, although sucrose decreased. At fully ripe stage, sugar composition was less responsive to treatments. These findings underscore the importance of genotype evaluation and the exploitation of genotype × treatment interactions in peppers breeding for sustainable farming. Full article

The management of Meloidogyne incognita often depends on chemical nematicides, which pose environmental and health risks. This study investigated the potential of bacterial strains isolated from uncultivated native soil as biocontrol agents and plant growth-promoting rhizobacteria (PGPR) in tomato plants artificially infected with this nematode. Fifteen strains were screened in vitro for nematicidal and ovicidal activity, and four promising strains (307, GB16, GB24, and GB29) were selected for greenhouse trials. All strains reduced the nematode reproduction factor and the number of nematodes/g of root. Strains 307 and GB24 showed the highest reductions, 61.39 and 57.24%, respectively. Despite some positive physiological trends, Bacillus spp. did not promote a significant increase in plant growth. Metabolomic analysis revealed that the strains produced a wide range of primary metabolites with potential nematicidal activity. All strains also secreted proteases and chitinases, enzymes linked to nematode cuticle degradation. Preliminary identification based on the 16S rRNA gene and phylogenetic analysis grouped the four strains into the Bacillus subtilis group (strains GB16, GB29 and 307) or Bacillus cereus group (strain GB24); however, genome sequencing will be required in future studies. Overall, strains 307 and GB24 demonstrated strong biocontrol potential, supporting their use as sustainable and complementary alternatives to chemical nematicides. Full article

Background/Objectives: Plant growth-promoting rhizobacteria (PGPR) have demonstrated potential for enhancing plant growth; existing research inadequately characterizes the metabolic underpinnings of PGPR-induced plant phenotypes. Methods: A deeper investigation into the impact of PGPR on plant metabolic pathways is crucial for a comprehensive understanding of their growth-promoting mechanisms and for the development of more effective biofertilizers and plant protection strategies. Results: To clarify the core metabolic pathways targeted by PGPR strains, we selected alfalfa as the research object, employed two Pseudomonas combinations, and utilized a broad-targeted metabolomics approach to investigate the metabolic characteristics of alfalfa roots. Through the analysis of primary and secondary metabolites, a total of 2694 metabolites were identified, among which lipids were the main nutrients during the growth of alfalfa. The L-citrulline and L-arginine contents were significantly upregulated, thereby affecting nitrogen metabolism and ultimately promoting plant growth. In addition, different branches of the isoflavonoid biosynthesis pathway showed differential regulation, indicating their close relationship with plant growth promotion. Conclusions: This study provides a new perspective for a deeper understanding of the molecular mechanisms by which PGPR promotes plant growth and lays a theoretical foundation for the future development of PGPR-based agricultural biological agents. Full article