Drought, a major abiotic stress, adversely affects the growth, development, and nutrient absorption of legume plants, leading to yield reduction. This study investigated the combined effects of silicon (Si) and the actinobacterial strain Streptomyces chartreusis on water-stress resistance in soybean (Glycine L.). Our experiments, conducted under simulated water deficit conditions, revealed that the combined application of Si and S. chartreusis boosted the morphological, physiological, and biochemical traits of the soybean plants. Si treatment led to higher levels of nitrogen, phosphorus, potassium, and silicon while reducing malondialdehyde (MDA) concentrations (25 %), an indicator of oxidative stress. The use of silicate and S. chartreusis boosted the activity of antioxidant enzymes, such as superoxide dismutase (35 %), catalase (61 %), and peroxidase (58 %), reducing oxidative damage and improving water relations, as shown by the increased relative water content (33 %) and membrane stability index (35 %). The plants treated with both silicate and S. chartreusis exhibited the highest levels of chlorophyll a and b, suggesting improved photosynthetic efficiency. These results highlight the potential of combining Si with beneficial microbial inoculants in sustainable agriculture to enhance soybean resilience to water stress. However, field studies are required to confirm the efficacy of these treatments in agricultural environments.

Many studies have investigated the toxic effects of microplastics (MPs) ingested by aquatic animals, but the effects of MPs that adhere to the roots of macrophytes require further exploration. Thus, the present study investigated the dose-dependent toxic effects of adding 10-500 mg/kg of polycaprolactam microplastics (PCM) on allelopathic cyanobacterial inhibition by a wetland macrophyte due to the influence on rhizosphere bacteria in a pot trial. First, comparisons of sterilized and unsterilized Iris pseudacorus rhizosphere soil showed that the unsterilized soil could enhance the root activity and allelopathic inhibition of Microcystis aeruginosa cyanobacteria. Furthermore, adding 50-100 mg/kg PCM to the unsterilized soil significantly altered the abundances of many types of bacteria, and decreased the root activity and bacterial biodiversity in the rhizosphere. Importantly, PCM changed the secondary metabolites profile in the roots, as well as decreasing production of the allelochemical palmitic acid and the allelopathic potential of I. pseudacorus. Moreover, a dominant strain of functional bacterium AAP51 was identified as an allelopathic promoter, isolated, and successfully inoculated into the sterilized soil. The decomposition of PCM produced the toxic monomer caprolactam in the rhizosphere soil at an average rate of 0.067 mg/kgd under treatment with 50 mg/kg PCM. Toxicological testing showed that 5 mg/kg caprolactam inhibited the activities of the dominant bacteria and expression of the allelopathic gene FAD2 to weaken the allelopathic effect of I. pseudacorus. Thus, the findings obtained in this study indicate that PCM inhibited the allelopathic potential of the macrophyte due to the release of toxic caprolactam damaging bacteria in the rhizosphere. Consequently, it is necessary to remove MP pollutants from aquatic ecosystems in order to maintain the strong allelopathic potential of macrophytes and efficiently control cyanobacterial blooms.

Soil salinization has been the major form of soil degradation under the dual influence of climate change and high-intensity human activities, threatening global agricultural sustainability and food security. High salt concentrations induce osmotic imbalance, ion stress, oxidative damage, and other hazards to plants, resulting in retarded growth, reduced biomass, and even total crop failure. Halo-tolerant plant growth promoting rhizobacteria (HT-PGPR), as a widely distributed group of beneficial soil microorganisms, are emerging as a valuable biological tool for mitigating the toxic effects of high salt concentrations and improve plant growth while remediating degraded saline soil. Here, the current status, harm, and treatment measures of global soil salinization are summarized. The mechanism of salt tolerance and growth promotion induced by HT-PGPR are reviewed. We highlight that advances in multiomics technologies are helpful for exploring the genetic and molecular mechanisms of microbiota centered on HT-PGPR to address the issue of plant losses in saline soil. Future research is urgently needed to comprehensively and robustly determine the interaction mechanism between the root microbiome centered on HT-PGPR and salt-stressed plants via advanced means to maximize the efficacy of HT-PGPR as a microbial agent. Halo-tolerant plant growth promoting rhizobacteria (HT-PGPR) are a valuable biological tool for mitigating the toxic effects of high salt concentrations. And the microbiome centered on HT-PGPR is solutions for sustainable agriculture in saline soils.

Using microbial cells for bioremediation requires evaluating suitable inoculation techniques and their effects. This study applied liquid and encapsulated in alginate beads inocula of A. vinelandii in agricultural soil to evaluate chlorpyrifos (CP) degradation and its impact on cytotoxic and genotoxic effects. Allium sativum cells and Eisenia foetida organisms were used as biomarkers for toxicological evaluations. Changes in the mitotic index and nuclear abnormalities in A. sativum cells were used for toxicity determinations. The percentage survival of E. foetida was calculated. Ultra-high-performance liquid chromatography was used to detect CP. The initial CP concentration (250 mg/kg) decreased by 92% when inoculated with liquid A. vinelandi and by 82% with A. vinelandii encapsulated after 14 d. A 60% decrease in cytotoxic and genotoxic damage to A. sativum cells was detected in treatments inoculated with A. vinelandii. The survival rate of E. foetida was improved by 33% when inoculated with free A. vinelandii compared to contaminated soil. Encapsulation as an inoculation strategy extended the viability of A. vinelandii compared to free inoculation. Both free and encapsulated inocula of A. vinelandii effectively degrade CP in soil and decrease its toxic effects. This study contributed by identifying sustainable agricultural alternatives for the inoculation and bioremediation of agricultural soils.

The utilization of plant growth-promoting rhizobacteria (PGPR) holds great promise for the restoration of damaged terrestrial plant ecosystems. However, there is a significant knowledge gap regarding the application of PGPR in rehabilitating aquatic ecosystems. In this study, we conducted a mesocosm experiment to investigate the effects of Raoultella ornithinolytica F65, Pantoea cypripedii G84, Klebsiella variicola G85, Novosphingobium profundi G86, and Klebsiella pneumoniae I109 on eelgrass ( Zostera marina L.), which is a crucial marine angiosperm. The application of these strains resulted in a significant increase in the new leaf area of eelgrass, with improvements of 55.4%, 14.4%, 39.1%, 20.6%, and 55.7% observed, respectively. Moreover, PGPR inoculation enhanced shoot biomass, rhizome elongation, leaf carbon and nitrogen content, as well as photosynthetic pigments. Furthermore, it stimulated enzymatic activities within the rhizosphere soil and positively influenced its physicochemical properties. The Illumina Miseq sequencing results revealed a positive shift in the bacterial community, leading to an enrichment of functional groups associated with nitrogen fixation and degradation of aromatic compounds. These findings underscore the significant potential of PGPR as a transformative tool for enhancing seagrass growth and survival, offering innovative strategies for the restoration of degraded seagrass meadows. This research not only advances our understanding of microbial-plant interactions in aquatic ecosystems but contributes to the broader goals of ecosystem revitalization and biodiversity conservation.

The ginseng industry's reliance on chemicals for fertilizer and pesticides has adversely affected the environment and decreased the quality of ginseng; therefore, microbial inoculum is an effective way to restore the damaged soil in ginseng fields. To investigate the effects of plant growth-promoting rhizobacteria (PGPR) and spent mushroom substrate (SMS) on soil and plant quality in ginseng, high throughput sequencing was performed to examine the microbial community structures in ginseng rhizosphere soil. All treatments significantly increased soil nutrient, enzyme activity, and ginseng biomass compared to control (p < 0.05). The combination of PGPR and SMS notably enhanced soil enzyme activities: urease (7.29%), sucrase (29.76%), acid phosphatase (13.24%), and amylase (38.25%) (p < 0.05). All treatments had different effects on ginseng rhizosphere soil microbial diversity. Significantly, the combination treatments enhanced microbial diversity by increasing the abundance of beneficial bacteria such as Allorhizobium-Neorhizobium-Pararhizobium-Rhizobium and Plectosphaerella, meanwhile suppressing harmful Klebsiella. The relative abundance of Fusarium was reduced to some extent compared with the application of SMS alone. The soil organic matter, available potassium, available phosphorus, and alkaline nitrogen, as key factors, influenced microbial community structures. Overall, the combination of PGPR and SMS positively impacted the rhizosphere environment and ginseng plant quality.

Background Oxidative stress mediated by reactive oxygen species (ROS) is a common denominator in arsenic toxicity. Arsenic stress in soil affects the water absorption, decrease stomatal conductance, reduction in osmotic, and leaf water potential, which restrict water uptake and osmotic stress in plants. Arsenic-induced osmotic stress triggers the overproduction of ROS, which causes a number of germination, physiological, biochemical, and antioxidant alterations. Antioxidants with potential to reduce ROS levels ameliorate the arsenic-induced lesions. Plant growth promoting rhizobacteria (PGPR) increase the total soluble sugars and proline, which scavenging OH radicals thereby prevent the oxidative damages cause by ROS. The main objective of this study was to evaluate the potential role of Arsenic resistant PGPR in growth of maize by mitigating arsenic stress. Methodology Arsenic tolerant PGPR strain MD3 (Pseudochrobactrum asaccharolyticum) was used to dismiss the 'As' induced oxidative stress in maize grown at concentrations of 50 and 100 mg/kg. Previously isolated arsenic tolerant bacterial strain MD3 Pseudochrobactrum asaccharolyticum was used for this experiment. Further, growth promoting potential of MD3 was done by germination and physio-biochemical analysis of maize seeds. Experimental units were arranged in Completely Randomized Design (CRD). A total of 6 sets of treatments viz., control, arsenic treated (50 & 100 mg/kg), bacterial inoculated (MD3), and arsenic stress plus bacterial inoculated with three replicates were used for Petri plates and pot experiments. After treating with this MD3 strain, seeds of corn were grown in pots filled with or without 50 mg/kg and 100 mg/kg sodium arsenate. Results The plants under arsenic stress (100 mg/kg) decreased the osmotic potential (0.8 MPa) as compared to control indicated the osmotic stress, which caused the reduction in growth, physiological parameters, proline accumulation, alteration in antioxidant enzymes (Superoxide dismutase-SOD, catalase-CAT, peroxidase-POD), increased MDA content, and H2O2 in maize plants. As-tolerant Pseudochrobactrum asaccharolyticum improved the plant growth by reducing the oxidation stress and antioxidant enzymes by proline accumulation. PCA analysis revealed that all six treatments scattered differently across the PC1 and PC2, having 85.51% and 9.72% data variance, respectively. This indicating the efficiency of As-tolerant strains. The heatmap supported the As-tolerant strains were positively correlated with growth parameters and physiological activities of the maize plants. Conclusion This study concluded that Pseudochrobactrum asaccharolyticum reduced the 'As' toxicity in maize plant through the augmentation of the antioxidant defense system. Thus, MD3 (Pseudochrobactrum asaccharolyticum) strain can be considered as bio-fertilizer.

Currently, in agriculture, there is a tendency towards the partial replacement of chemical pesticides with microbiological plant protection products. In this work, we tested the ability of plant-growth promoting bacteria from the genus Azospirillum to reduce the negative effects of high concentrations of six different pesticides on wheat characteristics. Of the seven Azospirillum strains studied, five showed high resistance to at least one pesticide, and Niveispirillum irakense (formerly classified as Azospirillum until 2014) was one of the most resistant strains to all pesticides. In most cases, catalase activity increased in resistant strains in the presence of pesticides. Furthermore, we demonstrated that some of the most resistant Azospirillum strains (including N. irakense, A. brasilense, A. picis, A. thiophilum, and A. baldaniorum) can counteract pesticide-induced growth inhibition, suppress oxidative stress, as evidenced by a decrease in iron-induced chemiluminescence and the amount of oxidative damage to wheat seedling mtDNA in a pot experiment. However, the bacteria had no positive effect on the chlorophyll content of wheat seedlings. Azospirilla were found in the rhizosphere of wheat roots 3 months after a wheat planting in the field experiment. Pesticides led to a slight decrease in their quantity in the rhizosphere. Additionally, bacterial inoculation mitigated the pesticide-induced decrease in wheat biomass.

Plants have limited resources to allocate to defences against infection and herbivory. While interactions between plant responses to microbial and herbivore attack are complex, it is often the case that the induction of one response will act antagonistically to the other. Recent studies have shown that plant growth promoting rhizobacteria, which improves overall plant health and general stress resistance, can enhance both anti-microbial and anti-herbivore defences. We investigated how soil application of the biofungicide Serenade ASO (Bacillus subtilis strain QST 713), which primes plant defences against fungal and bacterial infection and promotes plant growth, affects anti-herbivore defences by measuring both constitutive and induced defences. We applied Serenade one or two times to the soil of tomato plants and measured the numbers of type IV glandular trichomes on leaves, the weight gain of a generalist caterpillar (beet armyworms; BAW), and the activity of two enzymes associated with defence against insects (polyphenoloxidase and peroxidase). Serenade treated plants grew faster and foliage from treated plants had significantly higher numbers of glandular trichomes and higher polyphenoloxidase and peroxidase activities than untreated plants. However, Serenade treatment did not affect the degree of induction of plant defences when damaged by BAW feeding and did not slow the growth rate of BAW relative to plants not treated with Serenade. Therefore, the biofungicide Serenade increased plant growth and altered the densities of trichomes and the activities of two defensive enzymes in plants, but it did not affect overall susceptibility of the plants to a generalist herbivore.

Drought is one of the main devastating environmental factors limiting crops' development and productivity. This study investigated the role of combining intercropping and co-inoculation of arbuscular mycorrhizal fungi (AMF) and plant growth-promoting rhizobacteria (PGPR) to protect barley and alfalfa against drought damage. The experiment design consisted of four inoculation treatments: (1) non-inoculated plants (C), (2) plants inoculated with AMF consortium (AMF), (3) plants inoculated with the bacterial consortium (PGPR), and (4) plants co-inoculated with AMF + PGPR (AMF + PGPR), and two irrigation regimes: (i) well-watered, equivalent to 75% field capacity (FC), and (ii) drought, where watering was maintained at 35% FC. For each treatment (inoculated or not inoculated and stressed or not stressed), the plants of barley and alfalfa were monocropped and intercropped. Growth (shoots and roots dry weight), physiological (stomatal conductance and chlorophyll fluorescence), and biochemical (stress markers, osmolytes contents, and antioxidant enzyme activities) parameters were all measured. The results showed that applying intercropping and microbial inoculation AMF or/and PGPR enhanced the tolerance of plants to drought stress. The most pronounced effect was displayed by combining intercropping system and co-inoculation of AMF + PGPR, which improved shoot and root dry weight by 141 and 280% in barley and by 512 and 533% in alfalfa, respectively, compared to their respective uninoculated monocultures. Similarly, combining intercropping and co-inoculation with AMF + PGPR enhanced acid phosphatase, superoxide dismutase, and catalase activities by 125%, 161%, and 58% in barley and by 114%, 311%, and 112% in alfalfa, respectively, compared to their respective uninoculated monocultures. Furthermore, the thousand-seed weight was increased by 73% in barley intercropped and inoculated with AMF +PGPR. These findings revealed that intercropping barley and alfalfa and co-inoculation of AMF +PGPR may provide a sustainable approach to enhance drought tolerance, increase crop productivity, and promote food security.