Effect Of Plant Growth Promoting Rhizobacteria Research Articles

The Serratia sp. strain C2 confers tomato tolerance to high salt, virus infection and both stresses in combination

Besides increasing plant growth, several Plant Growth Promoting Rhizobacteria (PGPR), can enhance tolerance to biotic and/or abiotic stresses of numerous plant species. While cultivated plants are frequently subject to combined stresses in the field, there is limited knowledge of the effect of PGPR on plants undergoing simultaneous stress conditions. Therefore, we tested the beneficial properties of the halotolerant PGPR Serratia sp. strain C2, previously shown to enhance salt stress tolerance in barley, on tomato plants exposed to salinity, to Potato Virus Y (PVY) infection, and both stresses simultaneously. In our experimental conditions, C2 inoculation improved tomato tolerance to salt stress and positively correlated with a 46–68 % decrease in the level of PVY RNA compared to non-inoculated tomato plants. Morphometric, physiological and biochemical analyses (e.g., chlorophyll, sugar and proline accumulation, oxidative stress status and NDVI) indicated that C2 treatments had beneficial effects on tomato growth under simple and combined stress conditions. This is the first report of a PGPR enhancing tolerance not only to individually induced salinity and PVY infection, but also to both stresses in combination. Moreover, the expression analysis of selected genes involved in stress responses and RNA silencing-mediated antiviral immunity suggests that C2 can interfere with distinct defence response pathways to enhance stress tolerance in tomato. These pioneering results support the perspective of using PGPR as multi-spectrum and multi-host biostimulants for improving plant growth and protection from biotic, abiotic, and combined stresses to promote sustainable crop production in the face of environmental changes.

Enhancing Soybean Growth with Phytohormone-enriched PGPR Bioinoculants and Biofertilizers in Plant Stress Physiology

Background: The present investigation aimed to evaluate the effects of plant growth-promoting rhizobacteria (PGPR) bioinoculants and their carrier-based biofertilizers on the physiology of soybean. Methods: Seeds of two soybean varieties (cv. NARC-1 and cv. William-82) were either soaked in broth cultures of two PGPR strains, Planomicrobium chinense (MF616408) and Pseudomonas putida (KX574857), containing 106 cells/mL, or coated with biofertilizers. Three biofertilizers, namely biostimulant, biozote and biofert, were used. Result: Significant increases in root and shoot weight were observed with both liquid bioinoculants and carrier-based biofertilizers compared to the control. The consortium of P. chinense and P. putida resulted in the highest proline content and superoxide dismutase (SOD) activity. Biostimulant-treated plants exhibited higher catalase (CAT) activity and phenolics content. Indole-3-acetic acid (IAA) and gibberellic acid (GA) levels were enhanced in plants treated with PGPR and biofertilizers. Specifically, P. chinense and the biostimulant significantly promoted IAA content in cv. William-82, while biozote and P. chinense treatments increased GA content in both varieties. The consortium of P. chinense and P. putida showed the lowest ABA levels. The highest IAA/ABA and GA/ABA ratios were observed in plants treated with P. chinense. Liquid bioinoculants had a more pronounced effect on plant growth than carrier-based biofertilizers, though biofertilizers had stronger residual effects on rhizosphere soil organic matter. The combined effects of phytohormones, sugar, protein and proline production and antioxidant enzyme activity influenced plant growth and development.

Growth-promoting rhizobacteria improve physiological variables in lemon balm, Melissa officinalis L., subjected to water stress

Climate change has caused droughts in regions that previously did not have water issues, affecting the production of medicinal plants grown in small-scale agricultural units. Plants such as lemon balm, Melissa officinalis L., are sensitive to water stress, which reduces their yield. One alternative to mitigate water stress is the use of plant growth-promoting rhizobacteria (PGPR). However, in the high tropics of Colombia, the use of these microorganisms is not common due to a lack of knowledge about how they can improve water absorption and increase the yield of medicinal plants. This study aimed to determine the effect of native PGPR on lemon balm plants subjected to water stress conditions using a completely randomized design with six treatments and four replications. Applications of Bacillus cereus and Bacillus amyloliquefaciens were made, and the plants were subjected to two water levels (field capacity and 50% field capacity). Physiological variables of stomatal conductance, chlorophyll content, and fluorescence were measured at the end of the experiment. Bacillus cereus significantly improved growth parameters such as number of leaves (115.00±34.71), fresh weight of root (5.51±3.07 g) and shoot (8.32±4.27), Bacillus amyloliquefaciens increased stomatal conductance (401.3 μmol H2O m2 s1) in water-stressed plants. These results suggest that the use of native PGPR considerably improves the growth and development parameters of lemon balm plants and provides a viable alternative for farmers to enhance yield and resistance to water stress conditions.

Enhancing saffron (Crocus sativus L.) growth in the Kashmir valley with resilient and widely effective Plant Growth-Promoting Rhizobacteria (PGPR) under field conditions

This study provides a thorough examination of stress-tolerant plant growth-promoting rhizobacteria (PGPR) and their significance in enhancing plant growth and biocontrol activities, and influence on saffron cultivation in the Kashmir Valley. Quantitative analysis of 35 efficient PGPR revealed significant variability in plant growth promotion (PGP) attributes ranging from 60 to 653 µg/ml tri-calcium phosphate (TCP) solubilization, 1548–4311 nM α-ketobutyrate h/mg/protein ACC-deaminase activity, 1.4–74.8 µg/ml IAA-like auxins production, and 94–214 % siderophore production. Molecular fingerprinting disclosed 52 ERIC types that belonged to 25 genera, mainly Bacillus. Bacillus species including B. aryabhattai, B. halotolerans, B. methylotrophicus, B. safensis, B. siamensis and B. simplex dominated the PGPR population, along with Pseudomonas spp., such as P. azotoformans and P. chlororaphis, indicating a selective buildup of PGPR in the saffron rhizosphere. In-vivo and In-vitro dual inoculation test of these widespread PGPR and stress-tolerant also inhibited the mycelial growth of Fusarium species including F. oxysporum, F. oxysporum f. sp. ciceris, and F. proliferatum. The field application of seven selected PGPR strains resulted in significant improvements in saffron productivity, including increased sprouted corms, plant height, stigma length, and stigma fresh and dry weight, which ranged from 0.6-1.8 %, 0.4–0.7 %, 0.3–0.5 %, and 6–19 %, respectively. These strains have the potential to stimulate cormlet growth and ultimately increase saffron production. Therefore, the PGP traits of these stress-tolerant rhizobacteria contributing to nutrients solubilization, auxin biosynthesis, and fungicidal attributes can ameliorate the saffron agricultural practices.

Customized Plant Growth Promotion with Soil- and Cultivar-Compatible Microbial Biofertilizers

Organic fertilizers and microbial biofertilizers are now widely recognized to effectively complement traditional mineral fertilizers for plant growth. The present study shows that bio-organic fertilizers can be enhanced by the addition of functional plant-growth-promoting rhizobacteria (PGPR) that provide additional benefits to plants. We hypothesized that not all beneficial soil bacteria are functional in different farm soils and plant varieties; hence, the most effective PGPR that are suitable to each farm’s individual cropping conditions were selected. Five different field soils and their respective crops were tested for compatibility with six microbial biofertilizers (including three new bacterial strains) to supplement a commercially available bio-organic fertilizer. In pot trials with lucerne plants, four out of the six microbial treatments led to significant (p < 0.05) growth promotion benefits (up to 79.8% more leaves and dry weight) compared to mock-treated or bio-organic fertilizer-only-treated control plants. A trial with industrial hemp demonstrated that compatibility with PGPR occurs in a cultivar-specific manner, leading to growth promotion ranging from −3.4% to 68.9%, with each cultivar displaying a preference for a different PGPR. Finally, pot trials with Rhodes grass and two different soils demonstrated high yield increases compared to control plants, with Bacillus amyloliquefaciens 33YE being most effective for one soil and Bacillus velezensis UQ9000N/Pseudomonas lini SMX2 for the other soil. Yield advantages reduced after several cuts of grass, but a repeat biofertilizer treatment at 69 days after the initial treatment restored high yield advantages, with the same PGPR again being most effective. These results demonstrate the importance of customization of microbial inoculants to identify the most compatible PGPR–cultivar–soil interaction. The customization of microbial biofertilizers to soils and plant cultivars, combined with complementary fertilizer applications, can potentially lead to more reliable and more sustainable agricultural practices.

Effects of Individual and Combined Applications of Seaweed Extracts and Plant Growth-Promoting Rhizobacteria (PGPR) on Plant Growth and Physio-Biochemical Properties of Soft Wheat and Faba Bean

ABSTRACT The research on carbon materials and plants primarily focuses on their use in soil, showing variable effects. However, significant gaps exist regarding their impact under stress conditions (such as drought, salinity, etc.) and their interactions with plant physiological processes. Long-term effects on plant health and ecosystems are understudied, as are their interactions with other biofertilizers like algae extracts and plant growth-promoting rhizobacteria (PGPR). The aim of the present study was to evaluate the effects of seaweed extracts and PGPR on plant growth and some physio-biochemical properties of soft wheat (Triticum aestivum L.) and faba bean (Vicia faba L.). Two concentrations of aqueous extract from two seaweeds, Fucus spiralis (F) and Ulva rigida (U), and the PGPR bacillus strain solution S48 (S48S) were used either individually or in combination. All treatments were applied as foliar sprays. The findings showed that the combined application of Fucus spiralis extract [25%] (F), Ulva rigida extract [50%] (U), along with the PGPR S48 bacillus strain solution (S48S) promoted plant growth (50.93 cm for faba bean) and root development (17.90 cm for wheat). This treatment also resulted in increased chlorophyll content (3.25 mg/g Fresh Weight (FW) in soft wheat and 3.93 mg/g FW in faba bean), proteins (14.66 µg/mg FW in soft wheat and 23.79 µg/mg FW in faba bean), amino acids (0.46 mg/g FW in soft wheat and 0.56 mg/g FW in faba bean), and total carbohydrates (529.8 µg/ml in soft wheat and 340.7 µg/ml in faba bean) as compared to controls. On the other hand, the nitrate reductase activity was enhanced by seaweed extract application in both crops. Phosphorus (P) uptake by soft wheat and faba bean was significantly improved following the application of Ulva rigida extract [50%] (U), the PGPR S48 bacillus strain solution (S48S), and the co-treatment of Fucus spiralis extract [25%] (F) with the PGPR S48 bacillus strain solution (S48S). The findings suggest that the combined application of Fucus spiralis extract (F) and Ulva rigida extract (U) with the PGPR S48 bacillus strain solution (S48S) can significantly improve plant growth and nutrient absorption in durum wheat and faba bean. This offers a sustainable alternative to chemical fertilizers, reducing pollution and promoting healthier ecosystems. Furthermore, these biological treatments enhance plant resilience to abiotic stresses, potentially increasing yields in challenging conditions. By reducing reliance on chemical fertilizers, these practices can save money for farmers and advance sustainable agriculture.

Plant growth‐promoting rhizobacteria and Trichoderma shift common vetch (Vicia sativa) physiology and phyllosphere bacteria toward antagonism against anthracnose caused by Colletotrichum spinaciae

AbstractBackgroundPlant phyllosphere microbes are important for the host plant's protection. Plant growth‐promoting rhizobacteria (PGPR) and Trichoderma are common biocontrol agents (BCAs) for disease management. Pathogens and BCAs can change the rhizosphere microbial composition; however, the effect of PGPR or Trichoderma on plant phyllosphere microbes, particularly for mesocosms involving the interaction between pathogens and BCAs, is not well known.MethodsHigh‐throughput sequencing was used to identify the phyllosphere bacterial community of common vetch interacting with Colletotrichum spinaciae, two PGPRs (Bacillus subtilis and Bacillus licheniformis), and Trichoderma longibrachiatum. We evaluated anthracnose severity, phyllosphere bacteria diversity and composition, and the relationship between the activities of plant defense enzymes and hormonal molecules in plants treated with individual and combined inoculations of PGPRs, Trichoderma, and C. spinaciae.ResultsPGPR or Trichoderma alone reduced disease severity. Trichoderma reduced the salicylic acid content, PGPR increased the catalase activity in plants, and co‐inoculation of PGPR and Trichoderma decreased the salicylic acid content. Inoculation of PGPR and Trichoderma individually or in combination changed the disease‐associated phyllosphere bacteria, and this effect was related to plant defense enzymes and hormonal molecules.ConclusionsWe suggest that the plant defense response induced by PGPR and Trichoderma results in the enrichment of a fraction of favorable chloroplastic bacteria, which facilitates plant defense against diseases.

Effect of plant growth-promoting rhizobacteria (PGPR) on growth and yield of shallots on saline soils

Soil salinity is a limiting factor in agricultural productivity. One of the biological approaches to mitigate the impact of salt stress on plants is inoculating plant growth-promoting rhizobacteria (PGPR) to the plant roots. This study aimed to investigate the eff of PGPR dosage on the growth and yield of shallots at various salinity levels. This study was carried out in the experimental field of Poncokusumo, Malang. The treatments tested consisted of two factors. The first factor was soil salinity level, consisting of four levels: no salinity, NaCl 50 mM, NaCl 100 mM, and NaCl 150 mM. The second factor was PGPR concentration, consisting of four levels: no PGPR, PGPR 10 mL/L, PGPR 20 mL/L, and PGPR 30 mL/L. The sixteen treatment combinations were arranged in a randomized block design with three replications. The data obtained were subjected to the analysis of variance (ANOVA) at a significance level limit of 5%, followed by the Honestly Significant Difference (HSD) test at a 5% significance level for any significant differences. The results showed that the application of 30 mL/L of PGPR reduced EC of the soil and improved plant height, plant dry weight, leaf area, bulb diameter, bulb weight, and the number of bulbs per plant by 33%, 47.3%, 81%, 13%, 34.2%, 98.5%, and 31%, respectively, compared to the treatment without PGPR application under NaCl 150 mM salinity. The application of PGPR at 20 and 30 mL/L dosages significantly increased chlorophyll, flavonoid, and proline indices at NaCl at 100 mM and 150 mM salinity levels compared to the treatment without PGPR.

Effect of plant growth-promoting rhizobacteria in the hydroponic cultivation of basil (Ocimum basilicum L.)

Effect of plant growth-promoting rhizobacteria in the hydroponic cultivation of basil (Ocimum basilicum L.)

Improving Soil Quality and Yield of Intercropping-System Crops in a Dry Land Area through Plant Growth Promoting Rhizobacteria Application Frequency

The future of agriculture is prone to choose technology that can enhance the quality of the resources to support the sustainability of food production. Plant Growth Promoting Rhizobacteria (PGPR) is a reliable technology for future agriculture as it is environment-friendly, and able to optimize resource utilization and decrease external input. This research aimed to analyze the effect of PGPR (Pseudomonas fluorescens + Bacillus polymyxa) application frequency on chemical soil properties, a yield of an intercropping system in dry land, the in-between correlation of the parameters, and to determine the best PGPR application frequency. Randomized Complete Block Design (RCBD) was used in this research to put the treatment in the experimental unit properly. The treatments consisted of i) one-time application of PGPR at the planting time, ii) twice application of PGPR at the planting time and 15 Days After Planting (DAP), iii) three times application of PGPR at the planting time, 15 DAP and 30 DAP, iv) without application of PGPR as control. The results showed that PGPR application frequency improved chemical soil properties, yield, and total by-products as livestock feed. The activity of soil enzymes, nitrogenase, and phosphatase, was enhanced compared to the control. The application of PGPR in dryland areas is recommended to maintain soil fertility and support sustainable intercropping crop production. Further studies are needed to conduct mixed farming between agriculture, animal husbandry, clean energy (biogas), and organic fertilizer (residue from the biogas digester).

Plant Growth Promoting Rhizobacteria (PGPR): Impact on peanut flowering, seed physical quality, and yield determination (Arachis hypogaea L.)

Peanut seed yield is influenced by physiological and ecophysiological crop traits, with changes in reproductive parameters such as flowering time, flower number, and fertility index significantly affecting productivity. Management practices like Plant Growth-Promoting Rhizobacteria (PGPR) could enhance crop yield. PGPR can improve flowering and yield by modulating the balance of phytohormones and enhancing reproductive processes. This study assessed PGPR effects on peanut flowering dynamics, seed yield determination, and correlation with hormone levels. Two plant-level field experiments were conducted during 2019–2020 and 2020–2021, sowing two cultivars (ASEM 400 INTA and Granoleico) on four sowing dates (Oct-05, Oct-15, Nov-29, Dec-10). Three PGPR strains (Bacillus velezensis RI3 and SC6, Pseudomonas psychrophila P10), Bradyrhizobium japonicum, and control were arranged in a split-split-split-plot design, with sowing dates as main plots, cultivars as sub-plots, and PGPRs as sub-sub-plots. PGPR improved peanut flower number (FN) and flowering rate (FR) by 20 % and 50 % compared to B. japonicum and the control. B. velezensis SC6 showed the best performance (SC6 > P10 > RI3), advancing the flowering peak by 4–12 days. PGPR also increased the fertility index (FI) to 0.31 vs. 0.24 of B. japonicum and control and pod number (PN) by 53 % compared to the control. Flowering peak advancement led to larger seeds (SF≥8 mm) (∼+8 % vs. control) due to better environmental conditions (i.e., higher temperatures). Seed number (SN) increased by 94 %–113 % under PGPR treatments. Seed yield (SY) was increased (∼75 % on average) due to higher total biomass (TB) production and improved carbon allocation to seeds (harvest index; 0.33–0.36). Hormone analysis at the R5 stage under late sowing's restrictive conditions showed hormone level increases of 15 %–90 %. This study demonstrates that PGPR significantly improves peanut flowering dynamics, seed quality, and yield by affecting hormone levels and reproductive parameters, highlighting its potential as a sustainable management practice.

The use of combination plant growth promoting rhizobacteria to control chili leaf curl disease in the field

Plant growth-promoting rhizobacteria (PGPR) is a promising technology for controlling viral diseases, including pepper yellow leaf curl disease (PYLCD) of chili pepper caused by Begomovirus infection. The objectives of this research were to investigate the effectiveness of PGPR containing Pseudomonas fluorescens PF1 and Bacillus polymyxa BG25, as well as their combination with other protective agents, to control PYLCD under field conditions in an endemic region. The treatments consisted of a single application of PGPR (a mixture of P. fluorescens PF1 and B. polymyxa BG25), guano tea, endophytic fungus H5, and neem oil; combination of PGPR with guano tea, endophytic fungus H5, and neem oil; conventional pesticide that relies on synthetic chemical insecticide sprayed weekly; and untreated plots. The experiment was arranged in a randomized block design with four replications. Treatment with PGPR alone was able to delay disease onset by 2.25 weeks, but it caused only a slight reduction in disease incidence. The combination of PGPR + guano tea and PGPR + endophyte H5 provided the best results in controlling PYLCD. The combination of PGPR + guano tea and PGPR + endophyte H5 delayed disease onset by 2.75 weeks and 3.25 weeks, respectively, and reduced disease incidence with effectiveness rates of 52.72% and 52.08%, respectively. These two treatment combinations gave the best performance for plant growth and yield.

Application of Plant Growth Promoting Rhizobacteria on Vegetative Growth in Chili Plants (Capsicum frutescens L.)

Cayenne pepper is a significant plant in tropical regions, utilized not only as a culinary spice but also in the pharmaceutical industry. An effective strategy for enhancing the physical, chemical, and biological quality of soil is the employment of plant growth-promoting rhizobacteria (PGPR). PGPR, a soil microorganism that colonizes plant roots, can accelerate growth and protect against certain pathogens. The use of PGPR, particularly in biocontrol of plant pathogens and biofertilization, is prevalent across various global regions. This study evaluates the effectiveness of PGPR in boosting the growth of cayenne pepper and was conducted in Peresak Village, Narmada District, West Lombok Regency, NTB Province. The methodology implemented was a Completely Randomized Design (CRD) experiment with five treatments and five replications, totaling 25 plant units. The treatments included a control (P0 ml/L) and four PGPR concentrations: P1 (10 ml/L), P2 (20 ml/L), P3 (30 ml/L), and P4 (40 ml/L). Each PGPR dose was dissolved in 1 liter of water and administered at 200 ml per polybag. The findings indicated that PGPR application significantly impacted the growth of cayenne pepper plants, notably increasing plant height, leaf count, branch count, and flower count. The 30 ml/L PGPR concentration (P3) proved most effective in enhancing these growth parameters. The results underscore the substantial benefits of incorporating PGPR as a biofertilizer agent in agricultural practices to optimize crop yields.

Interactive effect of ambient and elevated levels of tropospheric ozone, nutrition and PGPR on growth and yield of chickpea (Cicer arietinum)

An experiment was conducted during 2020 and 2021 at ICAR-Indian Agricultural Research Institute, New Delhi, to study the interactive effect of nutrient and PGPR (Plant growth promoting rhizobacteria) on growth and yield of chickpea (Cicer aeritinum L.) cv. Pusa 3043 under ambient and elevated levels of ozone in FAOE (Free air ozone enrichment). A loss of 15–16% in dry matter production was observed under elevated ozone (EO3) when compared to ambient ozone (AO3) conditions. Seed treatment with PGPR was found to compensate for this loss as an increase in seed yield 18–19% was observed over untreated seeds. In terms of seed yield, the PGPR treatments with 75% nitrogen showed significant improvement compared to the recommended dose of fertilizer (RDF) application. A yield increase of 12% and 14% was observed with PGPR like RPAN8 (Anabena laxa) and An-Rh (Anabena torulosa with Mesorhizobium ciceri) (chickpea rhizobium) respectively, suggesting an advantage of an–Rh over RPAN8 under EO3. A combination of both PGPRs outperformed the individual PGPR, showing a 19% yield increase over RDF. This proves the potential of seed treatment with PGPR (RPAN8 and An-Rh) in ameliorating tropospheric ozone-induced stress in chickpea plants.

Synergy of plant growth promoting rhizobacteria and silicon in regulation of AgNPs induced stress of rice seedlings

Silver Nanoparticles (AgNPs), as an emerging pollutant, have been receiving significant attention as they deepen the concern regarding the issue of food security. Silicon (Si) and plant growth-promoting rhizobacteria (PGPR) are likely to serve as a sustainable approach to ameliorating abiotic stress and improving plant growth through various mechanisms. The present study aims to evaluate the synergistic effect of Si and PGPRs on growth, physiological, and molecular response in rice seedlings (Oryza sativa) under AgNPs stress. Data suggested that under AgNPs exposure, the root and shoot growth, photosynthetic pigments, antioxidant enzymes (CAT and APX), expression of antioxidant genes (OsAPX and OsGR), silicon transporter (OsLsi2), and auxin hormone-related genes (OsPIN10 and OsYUCCA1) were significantly decreased which accompanied with the overproduction of reactive oxygen species (ROS), nitric oxide (NO) and might be due to higher accumulation of Ag in plant cells. Interestingly, the addition of Si along with the AgNPs enhances the level of ROS generation, thus oxidative stress, which causes severe damage in all the above-tested parameters. On the other hand, application of PGPR alone and along with Si reduced the toxic effect of AgNPs through the improvement of growth, biochemical, and gene regulation (OsAPX and OsGR, OsPIN10 and OsYUCCA1). However, the addition of L-NAME along with PGPR and silicon drastically lowered the AgNPs induced toxicity through lowering the oxidative stress and maintained the overall growth of rice seedlings, which suggests the role of endogenous NO in Si and PGPRs mediated management of AgNPs toxicity in rice seedlings.

Mitigating microplastic stress on peanuts: The role of biochar-based synthetic community in the preservation of soil physicochemical properties and microbial diversity

Tire-derived rubber crumbs (RC), as a new type of microplastics (MPs), harms both the environment and human health. Excessive use of plastic, the decomposition of which generates microplastic particles, in current agricultural practices poses a significant threat to the sustainability of agricultural ecosystems, worldwide food security and human health. In this study, the application of biochar, a carbon-rich material, to soil was explored, especially in the evaluation of synthetic biochar-based community (SynCom) to alleviate RC-MP-induced stress on plant growth and soil physicochemical properties and soil microbial communities in peanuts. The results revealed that RC-MPs significantly reduced peanut shoot dry weight, root vigor, nodule quantity, plant enzyme activity, soil urease and dehydrogenase activity, as well as soil available potassium, and bacterial abundance. Moreover, the study led to the identification highly effective plant growth-promoting rhizobacteria (PGPR) from the peanut rhizosphere, which were then integrated into a SynCom and immobilized within biochar. Application of biochar-based SynCom in RC-MPs contaminated soil significantly increased peanut biomass, root vigor, nodule number, and antioxidant enzyme activity, alongside enhancing soil enzyme activity and rhizosphere bacterial abundance. Interestingly, under high-dose RC-MPs treatment, the relative abundance of rhizosphere bacteria decreased significantly, but their diversity increased significantly and exhibited distinct clustering phenomenon. In summary, the investigated biochar-based SynCom proved to be a potential soil amendment to mitigate the deleterious effects of RC-MPs on peanuts and preserve soil microbial functionality. This presents a promising solution to the challenges posed by contaminated soil, offering new avenues for remediation.

Study on Plant Growth Promoting Traits of PGPR Isolates From Semi-Arid Kachchh, Gujarat Under Salt Stress Conditions

Salinity is a major problem in the agricultural sector, as it turns productive agronomical land to become unproductive. Therefore, Plant-growth-promoting rhizobacteria (PGPR), that live in the plant root zone named the rhizosphere, is one of the prominent solutions to overcome this problem in an eco-friendly manner as Rhizobacteria responds to osmotic stress and support plant development. Thus, the present study was aimed to characterize various traits of the PGPR strains isolated from saline soils of Kachchh. The characterization of the traits in the presence and absence of sodium chloride was assessed including IAA production (76.97±1.68 mg/l), Ammonia production (38.59±0.19 mg/l), Siderophore production (49.21±1.83%), Phosphate solubilization (4897.73±25.53 mg/l). When assessed for the salt tolerance of the strains in the presence of NaCl between 20-50 gm/L, the strain D6 exhibited a better growth even at 5% NaCl concentration (2.047OD). Further, the effect of PGPR on the growth of V. radiata was 100% in all the experimental setup, whereas in case of B. juncea, the highest germination of 96.67% was observed only in T2 and T1+T2+T3. Further, the molecular sequencing of the strains revealed the identification of the strains as Klebsiella quasipneumoniae, Bacillus paralicheniformis and Klebsiella pneumoniae.

Efecto de un consorcio de rizobacterias para promover el crecimiento vegetal en lechuga (Lactuca sativa L.) y chile (Capsicum annuum L.)

Plant growth-promoting rhizobacteria (PGPR) are biostimulants that favor plant development. We evaluated the effect of PGPR in chilli pepper (Capsicum annuum L.) and lettuce (Lactuca sativa L.). An experimental design of 5 treatments and 4 replicates was used for each crop. The bacterial species were Achromobacter xylosoxidans (C56), Arthobacter pokkalii (JLB4), Bacillus pumilus (AV5) and their combination as a consortium. The variables evaluated were: plant height, shoot diameter, relative chlorophyll index (SPAD) and freshweight of aerial part. In these experiments were observed significant differences with C56 to stimulate 11% plant height compared with the other treatments. Bacterial consortium stimulates 7.8% the relative chlorophyll index in lettuce and showing a trend to stimulate freshweight in both plants. The use of PGPR in consortium is an alternative that should be further studied to minimize the use of chemicals, enhance agricultural practicese and mitigate climate change.

Comparative Analysis of Plant Growth-Promoting Rhizobacteria's Effects on Alfalfa Growth at the Seedling and Flowering Stages under Salt Stress.

Alfalfa (Medicago sativa L.), a forage legume known for its moderate salt-alkali tolerance, offers notable economic and ecological benefits and aids in soil amelioration when cultivated in saline-alkaline soils. Nonetheless, the limited stress resistance of alfalfa could curtail its productivity. This study investigated the salt tolerance and growth-promoting characteristics (in vitro) of four strains of plant growth-promoting rhizobacteria (PGPR) that were pre-selected, as well as their effects on alfalfa at different growth stages (a pot experiment). The results showed that the selected strains belonged to the genera Priestia (HL3), Bacillus (HL6 and HG12), and Paenibacillus (HG24). All four strains exhibited the ability to solubilize phosphate and produce indole-3-acetic acid (IAA) and 1-aminocyclopropane-1-carboxylate (ACC) deaminase. Among them, except for strain HG24, the other strains could tolerate 9% NaCl stress. Treatment with 100 mM NaCl consistently decreased the IAA production levels of the selected strains, but inconsistent changes (either enhanced or reduced) in terms of phosphate solubilization, ACC deaminase, and exopolysaccharides (EPS) production were observed among the strains. During the various growth stages of alfalfa, PGPR exhibited different growth-promoting effects: at the seedling stage, they enhanced salt tolerance through the induction of physiological changes; at the flowering stage, they promoted growth through nutrient acquisition. The current findings suggest that strains HL3, HL6, and HG12 are effective microbial inoculants for alleviating salt stress in alfalfa plants in arid and semi-arid regions. This study not only reveals the potential of indigenous salt-tolerant PGPR in enhancing the salt tolerance of alfalfa but also provides new insights into the mechanisms of action of PGPR.

Potential effect of plant growth-promoting rhizobacteria (PGPR) on wheat (Triticum aestivum L.) under salinity stress

Potential effect of plant growth-promoting rhizobacteria (PGPR) on wheat (Triticum aestivum L.) under salinity stress