Role Of Plant Growth Promoting Rhizobacteria Research Articles

Impact of Zinc Solubilizing Bacteria and Microbial Consortia on Growth and Yield of Rice (Oryza sativa L.)

Rice (Oryza sativa L.) is a staple food for over half the world's population, particularly in Asia. This study explores the potential of Zn-solubilizing microbes to enhance micronutrient content in rice, aiming to address these deficiencies sustainably. Beneficial free-living soil bacteria, specifically plant growth-promoting rhizobacteria (PGPR), were investigated for their role in improving plant health and yield. Twenty-two bacterial isolates were screened for Zn solubilization, with Enterobacter hormaechei identified as the most promising. Field experiments with rice varieties PD 26 and NDR 359 involved treatmentssuch asT1 (Control), T2 (ZnSB1: Enterobacter hormaechei MT507226.1), T3 (Consortium1: Pantoearodasii MZ397586 + Seratiamarcesecens MW843567), and T4 (Consortium2: Enterobacter hormaechei MT507226.1 + Pantoearodasii MZ397586 + Seratiamarcesecens MW843567). with individual and consortia of Zn-solubilizing bacteria. Significant improvements were shown in plant height, leaf area index (LAI), total chlorophyll, total dry matter (TDM), and grain yield. Results showed that Consortium1 (T3) significantly increased plant height by 7.94% for PD26 and 10.16% for NDR 359. Leaf Area Index (LAI) also improved notably under Consortium1, with increases of 15.56% for PD26 and 24.39% for NDR 359. Total chlorophyll content was highest under Consortium1 for PD26 (36.63% increase) and under Consortium2 for NDR 359 (31.41% increase). Total dry matter (TDM) showed substantial gains, especially in NDR 359 with Consortium2 treatment, achieving a 36.51% increase. Grain yield increased significantly across all treatments, with Consortium1 showing the highest yields: 12.26% for PD26 and 23.01% for NDR 359.Correlation analysis indicated strong positive relationships between plant height, TDM, and grain yield, underscoring the importance of these parameters in determining crop productivity. The findings suggest that microbial consortia, particularly Consortium1, can effectively replace traditional zinc fertilizers, enhancing sustainable agriculture by promoting plant growth and yield. These results are consistent with recent studies on the role of plant growth-promoting rhizobacteria (PGPR) in improving nutrient uptake and crop performance.

Deciphering the Nitrogen Fixation Gene Cluster in Vibrio natriegens: A Study on Optimized Expression and Application of Nitrogenase.

Microbial nitrogen fixation presents a viable alternative to chemical fertilizers, yet the limited colonization and specificity of naturally occurring nitrogen-fixing microorganisms present significant challenges to their widespread application. In this study, we identified a nitrogen fixation gene cluster (VNnif) in Vibrio natriegens (VN) and tested its nitrogenase activity through the acetylene reduction assay. We investigated the potential utilization of nitrogenase by incorporating the nitrogenase gene cluster from VN into plant growth-promoting rhizosphere bacteria Pseudomonas protegens CHA0 and enhancing its activity to 48.16 nmol C2H2/mg/h through promoter replacement and cluster rearrangement. The engineered strain CHA0-PVNnif was found to positively impact the growth of Arabidopsis thaliana col-0 and Triticum aestivum L. (wheat). This study expanded the role of plant growth-promoting rhizobacteria (PGPR) and provided a research foundation for enhancing nitrogenase activity.

Role of PGPR and silver nanoparticles on the physiology of Momordica charantia L. irrigated with polluted water comprising high Fe and Mn

The current investigation designed to estimate the bioremediation potential of plant growth-promoting rhizobacteria (PGPR) and Ag-nanoparticles. Tube well and HIT water comprising Mn and Fe above recommended values were used as treatments while tap water irrigation was treated as control. The HIT water showed 24, 200, and 64.11% higher content of Na, K Ca over control. Seeds were sterilized in 95% ethanol and soaked for 3 h before sowing in 73 h old culture of Pseudomonas stutzeri (Kx574858) @ 108 cells/ml. Phytotoxic effect of Fe and Mn reduce plant biomass and suppress photosynthetic activity indicates. The carotenoids, proline, and proline activity were 366, 450, and 678% higher in tube well water with combined PGPR and Ag-nanoparticles treatments. Pseudomonas stutzeri was more effective than Ag-nanoparticles to reduce oxidative stress with higher production of carotenoids, flavonoids, proline content, and enzyme SOD and CAT activities in HIT water. It is contingent that the high Mn and Fe bearing waste water enhance PGPR bioremediation potential to reduce metal stress in plants with synergistic action of PGPR and organic matter to alleviate oxidative stresses under metal stress. The residual effect of P. stutzeri on organic matter content of the rhizosphere soil and germination rate was higher for Momordica charantia L.

Medicinal plant-associated rhizobacteria enhance the production of pharmaceutically important bioactive compounds under abiotic stress conditions.

Interest in cultivating valuable medicinal plants to collect bioactive components has risen extensively over the world to meet the demands of health care systems, pharmaceuticals, and food businesses. Farmers commonly use chemical fertilizers to attain maximal biomass and yield, which have negative effects on the growth, development, and bioactive constituents of such medicinally important plants. Because of its low cost, environmentally friendly behavior, and nondestructive impact on soil fertility, plant health, and human health, the use of beneficial rhizobial microbiota is an alternative strategy for increasing the production of useful medicinal plants under both standard and stressed conditions. Plant growth-promoting rhizobacteria (PGPR) associated with medicinal plants belong to the genera Azotobacter, Acinetobacter, Bacillus, Brevibacterium, Burkholderia, Exiguobacterium, Pseudomonas, Pantoea, Mycobacterium, Methylobacterium, and Serratia. These microbes enhance plant growth parameters by producing secondary metabolites, including enzymes and antibiotics, which help in nutrient uptake, enhance soil fertility, improve plant growth, and protect against plant pathogens. The role ofPGPRin the production of biomass and their effect on the quality of bioactive compounds (phytochemicals) is described in this review. Additionally, the mitigation of environmental stresses including drought stress, saline stress, alkaline stress, and flooding stress to herbal plants is illustrated.

Role of plant growth-promoting rhizobacteria in boosting the phytoremediation of stressed soils: Opportunities, challenges, and prospects.

Soil is considered as a vital natural resource equivalent to air and water which supports growth of the plants and provides habitats to microorganisms. Changes in soil properties, productivity, and, inevitably contamination/stress are the result of urbanisation, industrialization, and long-term use of synthetic fertiliser. Therefore, in the recent scenario, reclamation of contaminated/stressed soils has become a potential challenge. Several customized, such as, physical, chemical, and biological technologies have been deployed so far to restore contaminated land. Among them, microbial-assisted phytoremediation is considered as an economical and greener approach. In recent decades, soil microbes have successfully been used to improve plants' ability to tolerate biotic and abiotic stress and strengthen their phytoremediation capacity. Therefore, in this context, the current review work critically explored the microbial assisted phytoremediation mechanisms to restore different types of stressed soil. The role of plant growth-promoting rhizobacteria (PGPR) and their potential mechanisms that foster plants' growth and also enhance phytoremediation capacity are focussed. Finally, this review has emphasized on the application of advanced tools and techniques to effectively characterize potent soil microbial communities and their significance in boosting the phytoremediation process of stressed soils along with prospects for future research.

A Review of Endophytes\' Ability to Promote Plant Development on Medicinal Herbs

Abstract: Countless microbes live in the bodies of animals and plants. Plant growth is aided by the interaction between microbes and plants. They can be used as bio-fertilizers because of their nutrient intake and nitrogen-fixing capacity. These bacteria produce important metabolites and secondary metabolites that can be used to treat cancer and other chronic human diseases. They play a key role in the decomposition of heavy metals in the soil. In other words, they have a positive impact on agriculture, medicine, biotechnology, and food science. Plant growth-promoting rhizobacteria (PGPR) are commonly used to improve the growth of a wide range of crops, such as seed germination, plant weight, and harvest yields. Plant development is triggered by PGPR colonization because bacteria produce plant hormones such as indole-3-acetic acid, cytokinin, and gibberellins, as well as enhanced mineral and nitrogen availability in the soil. They are also known to defend their host plants from harmful bacteria in some cases. The role of PGPR in connection to medicinal plants and their impact on the development of botanicals is an area where there is still a lot of research to be done. This review highlights the potential PGPR–medicinal plant interactions that could boost the medicinal plant's effectiveness, particularly in farmed plants. The significance of medicinal plant endophytic microbes for bioactive potentials.

Amelioration of Chromium-Induced Oxidative Stress by Combined Treatment of Selected Plant-Growth-Promoting Rhizobacteria and Earthworms via Modulating the Expression of Genes Related to Reactive Oxygen Species Metabolism in Brassica juncea.

Chromium (Cr) toxicity leads to the enhanced production of reactive oxygen species (ROS), which are extremely toxic to the plant and must be minimized to protect the plant from oxidative stress. The potential of plant-growth-promoting rhizobacteria (PGPR) and earthworms in plant growth and development has been extensively studied. The present study was aimed at investigating the effect of two PGPR (Pseudomonas aeruginosa and Burkholderia gladioli) along with earthworms (Eisenia fetida) on the antioxidant defense system in Brassica juncea seedlings under Cr stress. The Cr toxicity reduced the fresh and dry weights of seedlings, enhanced the levels of superoxide anion (O2•–), hydrogen peroxide (H2O2), malondialdehyde (MDA), and electrolyte leakage (EL), which lead to membrane as well as the nuclear damage and reduced cellular viability in B. juncea seedlings. The activities of the antioxidant enzymes, viz., superoxide dismutase (SOD), guaiacol peroxidase (POD), ascorbate peroxidase (APOX), glutathione peroxidase (GPOX), dehydroascorbate reductase (DHAR), and glutathione reductase (GR) were increased; however, a reduction was observed in the activity of catalase (CAT) in the seedlings under Cr stress. Inoculation of the PGPR and the addition of earthworms enhanced the activities of all other antioxidant enzymes except GPOX, in which a reduction of the activity was observed. For total lipid- and water-soluble antioxidants and the non-enzymatic antioxidants, viz., ascorbic acid and glutathione, an enhance accumulation was observed upon the inoculation with PGPR and earthworms. The supplementation of PGPR with earthworms (combined treatment) reduced both the reactive oxygen species (ROS) and the MDA content by modulating the defense system of the plant. The histochemical studies also corroborated that the combined application of PGPR and earthworms reduced O2•–, H2O2, lipid peroxidation, and membrane and nuclear damage and improved cell viability. The expression of key antioxidant enzyme genes, viz., SOD, CAT, POD, APOX, GR, DHAR, and GST showed the upregulation of these genes at post-transcriptional level upon the combined treatment of the PGPR and earthworms, thereby corresponding to the improved plant biomass. However, a reduced expression of RBOH1 gene was noticed in seedlings supplemented under the effect of PGPR and earthworms grown under Cr stress. The results provided sufficient evidence regarding the role of PGPR and earthworms in the amelioration of Cr-induced oxidative stress in B. juncea.

The Role of Plant Growth-Promoting Rhizobacteria (PGPR) in Mitigating Plant’s Environmental Stresses

Phytoremediation is a cost-effective and sustainable technology used to clean up pollutants from soils and waters through the use of plant species. Indeed, plants are naturally capable of absorbing metals and degrading organic molecules. However, in several cases, the presence of contaminants causes plant suffering and limited growth. In such situations, thanks to the production of specific root exudates, plants can engage the most suitable bacteria able to support their growth according to the particular environmental stress. These plant growth-promoting rhizobacteria (PGPR) may facilitate plant growth and development with several beneficial effects, even more evident when plants are grown in critical environmental conditions, such as the presence of toxic contaminants. For instance, PGPR may alleviate metal phytotoxicity by altering metal bioavailability in soil and increasing metal translocation within the plant. Since many of the PGPR are also hydrocarbon oxidizers, they are also able to support and enhance plant biodegradation activity. Besides, PGPR in agriculture can be an excellent support to counter the devastating effects of abiotic stress, such as excessive salinity and drought, replacing expensive inorganic fertilizers that hurt the environment. A better and in-depth understanding of the function and interactions of plants and associated microorganisms directly in the matrix of interest, especially in the presence of persistent contamination, could provide new opportunities for phytoremediation.

Antagonistic Potential of Bacterial Species against Fungal Plant Pathogens (FPP) and Their Role in Plant Growth Promotion (PGP): A Review

Since the 19th century to date, the fungal pathogens have been involved in causing devastating diseases in plants. All types of fungal pathogens have been observed in important agricultural crops that lead to significant pre and postharvest losses. The application of synthetic fungicide against the fungal plant pathogens (FPP) is a traditional management practice but at the same time these fungicides kill other beneficial microbes, insects, animal, and humans and are harmful to environment. The antagonistic microorganism such as bacteria are being used as an alternate strategy to control the FPP. These antagonistic species are cost-effective and eco-friendly in nature. These biocontrol bacteria have a broad mechanism against fungal pathogens present in the phyllosphere and rhizosphere of the plant. The antagonistic bacteria have different strategies against the FPP, by producing siderophore, biofilm, volatile organic compounds (VOCs), through parasitism, antibiosis, competition for limited resources and induce systemic resistance (ISR) in the host plant by activating the immune systems. The commercial bio-products synthesized by the major bacterial species Pseudomonas syringae, Burkholderia cepacia, Streptomyces griseoviridis, Pseudomonas fluorescens and Bacillus subtilis are used to control Fusarium, Pythium, Rhizoctonia, Penicillium, Alternaria, and Geotrichum. The commercial bio-formulations of bacteria act as both antifungal and plant growth regulators. The Plant growth-promoting rhizobacteria (PGPR) played a significant role in improving plant health by nitrogen-fixing, phosphorus solubilization, phytohormones production, minimizing soil metal contamination, and by ACC deaminase antifungal activities. Different articles are available on the specific antifungal activity of bacteria in plant diseases. Therefore, this review article has summarized the information on biocontrol activity of bacteria against the FPP and the role of PGPR in plant growth promotion. This review also provided a complete picture of scattered information regarding antifungal activities of bacteria and the role of PGPR.

Role of PGPR on the physiology of sunflower irrigated with produced water containing high total dissolved solids (TDS) and its residual effects on soil fertility

The present study was conducted to evaluate the bioremediation potential of plant growth-promoting rhizobacteria (PGPR) PGPR isolates from high total dissolved solids (TDS) bearing produced water on the water quality, soil physicochemical properties and growth and physiology of sunflower irrigated with high TDS bearing produced water having salinity level 130 times higher above seawater and also containing traces of oil and grease. Seeds of sunflower hybrid Parsun 3 were soaked for 3–4 h prior to sowing in 72 h old culture of PGPR strains W1 and W2 isolated from high TDS bearing polluted water. The control plants were irrigated with 90% diluted TDS water supplemented with 5 ml LB media. Whereas, the inoculated plants were irrigated with 90% diluted TDS water supplemented with 5 ml PGPR inocula.in LB media. The plants were grown under natural conditions. The 16S rRNA sequence analyses identified the isolate W1 bearing 100% similarity with the plant growth-promoting rhizobacteria (PGPR) Ralstonia pickettii and W2 bearing 99.7% similarity with Brevibacillus invocatus. Both the isolate were catalase and oxidase positive. The Ralstonia pickettii and Brevibacillus invocatus treatments decreased the EC and TDS values significantly such that the EC and TDS values of 90% diluted TDS water were 29 times and 19 times higher than tap water. Sodium adsorption ratio (SAR), organic matter, nitrogen, potassium, magnesium and carbon content were 1.96, 1.10, 2.28 1.20, 6.63 and 1.00 times greater than control in the rhizosphere soil of Ralstonia pickettii inoculated plants irrigated with high TDS bearing water There were significant increases in plant growth, sugar, flavonoids and phenolics, chlorophyll b, total chlorophyll, carotenoids content and activities of superoxide dismutase, catalase and peroxidase in plants inoculated with Ralstonia pickettii and Brevibacillus invocatus. The flavonoids, phenolics and proline contents were 0.54, 0.72 and 0.30 times higher in Ralstonia pickettii inoculated plants. Shoot/root dry weight ratio was about (50%) lower than control in Ralstonia pickettii and Brevibacillus invocatus treatments. Ralstonia pickettii was more effective than Brevibacillus invocatus to combat oxidative and osmotic stresses. It is inferred that the high TDS bearing produced water from oil factory harbor Plant growth-promoting rhizobacteria (PGPR) having the potential to combat high salinity stress in plants when used as bioinoculant. The broth culture containing the bacteria may be supplemented with the saline water used for irrigation as it provides nutrients for the growth and proliferation of bacteria present in the saline water and hence the synergistic action of bacterial inocula with the indigenous bacteria present in saline water may better alleviate osmotic and oxidative stresses of plants encountered under salinity stress. The residual effect of Ralstonia pickettii on organic matter and Ca, Mg, K and P content of the rhizosphere soil was notably higher for succeeding crops. Novelty statement This is the first report demonstrating that rhizobacteria can proliferate in water containing salinity higher above seawater in addition to oil grease and TSS. Their efficiency to reduce TDS can be augmented by an exogenous supply of LB broth culture of PGPR isolated from the polluted water. These indigenous rhizobacteria when used as bioinoculant on the plant can act as plant growth promoters as well as bioremediation of salinity effects.

Unsnarling Plausible Role of Plant Growth-Promoting Rhizobacteria for Mitigating Cd-Toxicity from Plants: An Environmental Safety Aspect

Unsnarling Plausible Role of Plant Growth-Promoting Rhizobacteria for Mitigating Cd-Toxicity from Plants: An Environmental Safety Aspect

Insight Into the Role of PGPR in Sustainable Agriculture and Environment

A multitude of roles is played by microbes in food and agriculture that include nutrient cycling and management, organic matter decomposition and fermentation. Plant growth promoting rhizobacteria (PGPR), representing microbial groups and with ability of colonizing plant roots, influence plant growth through various indirect and direct modes in order to promote its growth and/or protect it from diseases or damage due to insect attack. Thus, PGPR research has received renewed interest worldwide. Increasing number of crop-specific PGPR are being commercialized these days. Approaches like seed-inoculation and soil application either alone or in combination with bacterial culture/product for increased nutrient availability through phosphate solubilisation, potassium solubilisation, sulfur oxidation, nitrogen fixation, iron, and copper chelation are gaining popularity. Arbuscular mycorrhizal fungi (AMF) are root fungal symbiont that improve management of abiotic stress such as phosphorus deficiency. PGPR involves roles like production of indole acetic acid (IAA), ammonia (NH3), hydrogen cyanide (HCN), catalase, etc. PGPR also improve nutrient uptake by altering the level of plant hormone that enhances root surface area by increasing its girth and shape, thereby helping in absorbing more nutrients. PGPR facilitate seed germination, seedling growth and crop yield. An array of microbes includingPseudomonas, Azospirillum, Azotobacter, Klebsiella, Enterobacter, Alcaligenes, Arthrobacter, Burkholderia, Bacillus, andSerratiaenhance plant growth. VariousPseudomonassp. have demonstrated significant increase in germination, seedling growth and yield in different agricultural crops, including wheat. Hence, developing a successful crop-specific PGPR formulation, the candidate should possess characteristics like high rhizosphere competence, extensive competitive saprophytic ability, growth enhancing ability, ease of mass production, broad-spectrum action, safety toward the environment and compatibility with other partnering organisms.

Impact of nanochitosan and Bacillus spp. on health, productivity and defence response in Zea mays under field condition.

The online version contains supplementary material available at 10.1007/s13205-021-02790-z.

Role of Rhizobium on Growth and Development of Groundnut: A Review

To fulfill the demand of increased population it is very essential to enhance crop productivity with precise inputs. Non-judicious application of inorganic fertilizers and other agrochemicals is degrading soil health, creating environmental pollution and also contributing to climate change. Nowadays, people became more aware towards health risks and demand for quality foods with less chemical residues is increasing as there is a progression of demand for organic products. But it is very difficult to produce adequate quantity of organic foods for the raised population in the developing countries as per standard organic practices. That’s why judicious use of inorganic fertilizers, organic manures and biofertilizers is required to supply nutrients to crops. Plant growth promoting rhizobacteria (PGPR), such as Rhizobium inoculation in groundnut (a major oilseed crop) can boost crop growth and enhance yield in a sustainable manner. Further, Rhizobium has multifaceted advantages in crop nutrient uptake and soil quality improvement. The article described the role of PGPR as well as Rhizobium in growth and productivity of groundnut towards production sustainability.

Mixed inoculum of rhizobacteria and arbuscular mycorrhizal fungus enhance diosgenin contain and phosphorus uptake in fenugreek under drought stress

There is considerable evidence to increase diosgenin and other medicinally useful compounds production in fenugreek with microbial inoculations. Fenugreek (Trigonella foenum-graecum L.), as an annual medicinal plant, is extensively cultivated in most regions of the world. In the present study we evaluate the role of plant growth-promoting rhizobacteria (PGPR) inocula (Pseudomonas putida and Bradyrhizobium japonicum) alone or in combination with an arbuscular mycorrhizal fungus(AMF) (Glomus intraradices) on diosgenin content, some biochemical characteristics and phosphorus accumulation of fenugreek plants subjected to drought stress. ACC deaminase activity was detected in both bacteria and it was 2.1 fold higher in B. japonicum than the P. putida. Results showed that diosgenin content was commonly higher in leaves under non-stress vs drought stress condition. In non-stress, plants with dual inoculation (G. intraradices and B. japonicum) resulted in highest diosgenin content significantly different with other treatments. The leaf proline content was the highest in plant subjected to drought stress with dual inoculation (G. intraradices and P. Putida), whereas the highest total soluble proteins was belonged to plants with triple inoculation(P. putida, B. japonicum and G. intraradices). Bacterial and fungal inoculation decreased peroxidase activity both in stress and non-stress condition. The highest amount of phosphorous in the roots was assigned to single inoculation with P. putida in stress and with G. intraradices in non-stress condition. The present study provides a good insight on the effect of PGPR and AMF on diosgenin content as a major bioactive constituent.

Role of Plant Growth-Promoting Rhizobacteria (PGPR) and Bio-Control Agents (BCAs) in Crop Production

The bioagents like Plant Growth Promoting Rhizobacteria (PGPR) and Biocontrol Agents (BCAs) play a crucial role in plant growth promotion, nutrient uptake and suppression of biotic and abiotic stresses. Different researchers have applied these bioagents by various means either through seed treatment or through soil application to prevent various plant diseases. Thus, these non-chemical environment friendly tools can be exploited to enhance crop production.

The role of plant growth-promoting rhizobacteria (PGPR) in improving iron acquisition by altering physiological and molecular responses in quince seedlings

Due to insoluble iron (Fe) sources in soil, limited Fe availability leads to the disruption of the photosynthetic apparatus; this affects the growth and productivity of plants such as quince (Cydonia oblonga) that are very sensitive to low Fe content. Plant growth-promoting rhizobacteria (PGPR) play an important role in the regulation of Fe uptake under its limited availability. Therefore, in this research, two PGPR (Pseudomonas fluorescens and Microccucuce yunnanensis), at two Fe levels [50 μM (Fe-sufficiency) or 5 μM (Fe-deficiency)], were used to investigate the impact of the given bacteria on improving the acquisition of Fe in quince seedlings. Upon Fe-deficiency, the highest shoot and root biomass (7.14 and 6.04 g plant−1 respectively), the greatest chlorophyll concentration (0.89 mg g−1FW), and the largest Fe concentrations in roots and shoots (30% and 48.7%, respectively) were shown in the quince treated with M. yunnanensis. Both PGPR increased the root citric acid and the phenolic compound concentration. Two days after Fe-deficiency and PGPR treatments, a 1.5- fold increase, was observed in the expression of HA7. The highest PAL1 gene expression and the greatest PAL activity (95.76 μmol cinnamic acid g−1FW) were obtained from the M. yunnanensis treatment. The expression of the FRO2 gene was also affected by Fe-deficiency and PGPR treatments, resulting in an increase in the FCR activity and a surge in the Fe concentrations of leaves and roots. It could, therefore, be concluded that the PGPR modulated Fe acquisition in the quince seedlings upon Fe-deficiency by influencing the physico-chemical and molecular responses.

Variable Influences of Water Availability and Rhizobacteria on the Growth of Schizachyrium scoparium (Little Bluestem) at Different Ages.

There is significant interest in understanding the role of plant growth-promoting rhizobacteria (PGPR) in alleviating different types of plant stress. Schizachyrium scoparium (little bluestem) is a moderately drought tolerant, perennial bunchgrass native to North America. The goal of this experiment was to evaluate whether the addition of a bacterial root isolate in the Pseudomonas genus promoted the growth of S. scoparium with changes in water availability. Pseudomonas are common rhizobacteria and have been shown to improve plant growth. It was hypothesized that plants inoculated with the PGPR strain would have greater growth and health, and would be less affected by shifts in water availability. Pseudomonas strains were isolated from the roots of native S. scoparium plants. After germination, S. scoparium seedlings were subjected to four treatment groups: low water; high water; low water with PGPR; and high water with PGPR. The experiment was run three times with plants at different starting ages; 14-, 28-, and 70-day-old plants. The effects of the water and PGPR treatments were variable between the experimental trials. There were no significant effects of the water treatments on plant growth in Trial 1 (14-day-old plants) or Trial 2 (28-day-old plants), however, there was a significant negative effect of the high watering treatment on the shoot length and biomass in Trial 3. High water availability was significantly associated with greater plant health in Trial 1, but appeared to reduce plant health in Trials 2 and 3. The PGPR treatment appeared to promote root growth and biomass in Trial 2, and was associated with greater plant health in all three trials, especially when paired with the low water treatment. Results from a permutational MANOVA indicate that plant growth was significantly different between the trials due to differences in the starting age of the plants and the duration of the experiments. Thus, methodological choices, such as plant life history stage and experiment duration, may affect the response of plants to PGPR in the rhizosphere. This research provides an insight into the interactions between PGPR and water availability on the growth and health of native plants.

Optimization of production technology of pea (Pisum sativum L.) enriched plant growth Rhizobacteria

Abstract Pea (Pisum sativum L.) having capability to harbor plant growth promoting rhizobacteria.The experiment was conducted to examine, the effect of plant growth promoting rhizobacteria (PGPRs) single or in addition with L-tryptophan, a precursor of auxin on production of Pisum sativum L. Experiment was conducted at the vegetable area, Delma Island United Arab Emirates. Seeds of Pisum sativum L.) cultivars viz. Meteor, Alina Pak, Climax and Pea- 2009 were treated with FF-34 (Pantoea sp.), (Burkholderia phytofirmans), FF-34+L-Tryptophan, PsJN PsJN+L-Tryptophan, water (positive control) whereas untreated seeds assisted as control. Data were collected concerning various parameters such as plant emergence percentage, plant height, branches number plant-1, chlorophyll content, days to 1st flowering, days from flowering to 1st pod maturity, number of pods per plant, pod length, seeds number pod-1, fresh and weight of dry plant, harvest index and hundred seed weight. Pea varieties Pea-2009 and Climax excelled over all other varieties for some traits. Among seed treatments FF-34 exhibited better results for maximum parameters. Results signify the role of PGPRs in Pea growth and productivity. Keywords: Inoculation; L-tryptophan; Pisum sativum; Pods maturity; Rhizobacteria http://dx.doi.org/10.19045/bspab.2018.700186

Plant growth promoting rhizobacteria induced Cd tolerance in Lycopersicon esculentum through altered antioxidative defense expression

The present study was designed to determine the role of plant growth-promoting rhizobacteria (Pseudomonas aeruginosa &Burkholderia gladioli) in alleviating Cd stress in Lycopersicon esculentum. Cd concentration of 0.4 mM enhanced superoxide anions, MDA and H2O2 by 136%, 378% and 137% that also caused nuclear and cell viability damage. Cd enhanced the activities of enzymatic antioxidants such as CAT, GST, GPOX, DHAR, and GR by 64%, 126%, 265%, 25% and 93% respectively. However, SOD, POD and PPO was decreased by Cd and enhanced by 119%, 198% and 42% by inoculation of P. aeruginosa and 65%, 119% and 33% by B. gladioli. The contents of non-enzymatic antioxidants and total antioxidants (WSA, LSA) were also enhanced in response to metal stress and reduced by supplementation with PGPR. Confocal microscopy revealed improved cell viability and decreased nuclear damage in Cd-treated L. esculentum roots supplemented with PGPRs. Gene expression studies conducted through qRT-PCR revealed that expression levels of the SOD, POD, and PPO genes were enhanced by 478%, 830% and 253%, while the expression of CAT, GR, GST, GPOX, and APOX genes decreased by 97%, 87%, 75%, 82%, 88% in P. aeruginosa-inoculated Cd-treated seedlings. Also, B. gladioli elevated the expression of SOD, POD and PPO genes and reduced the expression of CAT, GR, GPOX, APOX and GST genes respectively. Therefore, the results suggest that Cd induced oxidative stress in L. esculentum seedlings was reduced by PGPRs through modulation of antioxidative defence expression as demonstrated in terms of antioxidants both quantitatively as well as qualitatively.