Potential Of Plant Growth Promoting Rhizobacteria Research Articles

The Biotechnological Potential of Plant Growth-Promoting Rhizobacteria Isolated from Maize (Zea mays L.) Cultivations in the San Martin Region, Peru.

Maize (Zea mays L.) is an essential commodity for global food security and the agricultural economy, particularly in regions such as San Martin, Peru. This study investigated the plant growth-promoting characteristics of native rhizobacteria isolated from maize crops in the San Martin region of Peru with the aim of identifying microorganisms with biotechnological potential. Soil and root samples were collected from maize plants in four productive zones in the region: Lamas, El Dorado, Picota, and Bellavista. The potential of twelve bacterial isolates was evaluated through traits, such as biological nitrogen fixation, indole acetic acid (IAA) production, phosphate solubilization, and siderophore production, and a completely randomized design was used for these assays. A completely randomized block design was employed to assess the effects of bacterial strains and nitrogen doses on maize seedlings. The B3, B5, and NSM3 strains, as well as maize seeds of the yellow hard 'Advanta 9139' variety, were used in this experiment. Two of these isolates, B5 and NSM3, exhibited outstanding characteristics as plant growth promoters; these strains were capable of nitrogen fixation, IAA production (35.65 and 26.94 µg mL-1, respectively), phosphate solubilization (233.91 and 193.31 µg mL-1, respectively), and siderophore production (34.05 and 89.19%, respectively). Furthermore, molecular sequencing identified the NSM3 isolate as belonging to Sporosarcina sp. NSM3 OP861656, while the B5 isolate was identified as Peribacillus sp. B5 OP861655. These strains show promising potential for future use as biofertilizers, which could promote more sustainable agricultural practices in the region.

Biocontrol potential of plant growth-promoting rhizobacteria against plant disease and insect pest

Biocontrol potential of plant growth-promoting rhizobacteria against plant disease and insect pest

Phosphate-solubilizing rhizobacteria and their effects on the growth and phosphorus uptake by wheat plants

Wheat represents a fundamental component of the diet that contributes to ensuring global food security. However, its cultivation faces various abiotic and biotic constraints that result in fluctuating yields. The use of plant growth promoting rhizobacteria (PGPR) with the ability to solubilize phosphate presents itself as an environmentally friendly solution aimed to at enhancing sustainable agriculture practices. The objective of the present study is to assess the potential of PGPR in augmenting both yield and phosphorus (P) levels in wheat plants (Triticum durum L). under semi-controlled environmental conditions. Initially, the strains under investigation were screened for their capacity to dissolve different forms of mineral complex P, along with other plant growth promoting attributes such as iron chelation, Indole acetic acid (IAA) production, nitrogen fixation, and production of exopolysaccharides. Plant response to inoculation with PGPR was studied through an experiment conducted in a greenhouse involving four distinct treatments: (1) Control plants without any inoculation, (2) Inoculation with the PGP27 strain (Rahnella aquatilis), (3) Inoculation with the PGP25 strain (Erwinia persicina), and (4) Inoculation with the PGP374 strain (Raoultella terrigena). Results demonstrated that the studied strains exhibited significant promoting activities, including the solubilization of complex phosphate, the production of exopolysaccharides, IAA, siderophores, and atmospheric nitrogen fixation. Furthermore, the inoculation of plants with PGPR led to an increase in both biomass and plant phosphate concentrations, surpassing those observed in the control group. In conclusion, the findings propose that species like Raoultella and Erwinia have the potential to offer agronomic advantages as rhizobacteria that promote plant growth.

Amelioration of drought stress in wheat by using plant growth-promoting rhizobacteria and biogas slurry

<p>Drought stress has a significant impact on cereal-based staple food production, particularly in developing countries like Pakistan. To ensure a sustainable and reliable food supply, it is essential to develop comprehensive production plans that incorporate various approaches to mitigate the effects of drought. In a study conducted using a randomized complete block design, we investigated the potential of plant growth-promoting rhizobacteria (PGPR) and biogas Slurry (BGs) either individually or in combination to alleviate drought stress at different stages of wheat growth. The two-year field research demonstrated that the application of Azosprillium lipoferum with biogas slurry resulted in improved water relations, chlorophyll content, grain quality, yield, and related characteristics in wheat plants compared to the stressed treatments. Particularly, the combined treatment of PGPR and BGs exhibited the most favorable outcomes. Notably, the combined treatment effectively mitigated drought stress by significantly increasing antioxidant levels (17% APX, 29% POD, 34% CAT, and 41% SOD) during the grain-filling stage (GFS) compared to the controls. The combined treatment resulted in a remarkable 40% improvement in the respective controls at the GFS stage. Overall, the combined use of PGPR and BGs was identified as an effective strategy to enhance the resilience of wheat plants to drought, particularly in arid and semi-arid regions.</p>

Unlocking the Potential of Plant Growth-Promoting Rhizobacteria to Enhance Drought Tolerance in Egyptian Wheat (Triticum aestivum)

Plant growth-promoting rhizobacteria (PGPRs) represent a promising strategy for enhancing plant resilience and yields under drought-stress conditions. This study isolated and characterized PGPR from wheat rhizosphere soil in Egypt. Four PGPR strains were evaluated for an array of plant growth-promoting traits, including IAA production, biofilm formation, siderophore production, nitrogen fixation, ACC deaminase activity, phosphate solubilization, and antagonistic potential. Molecular identification via 16S rRNA sequencing classified three isolates (MMH101, MMH102, and MMH103) within the Bacillus genus and one isolate (MMH104) as Myroides sp. Greenhouse experiments examined the effects of PGPR inoculation on the drought-stressed Egyptian wheat cultivar, Gimmeza-9. Wheat plants inoculated with PGPR isolates showed dramatic improvements in growth parameters and stress tolerance indicators compared to non-inoculated controls when subjected to a 10-day drought period, with Bacillus rugosus (MMH101) inoculation resulting in increases of 61.8% in fresh biomass, 77.2% in dry biomass, 108.5% shoot length, and 134.9% root length. PGPR treatments also elevated the chlorophyll and proline content while reducing malondialdehyde levels. The findings demonstrate the effectiveness of PGPR inoculation in enhancing the morphology, physiology, and drought stress resilience of wheat. Isolated PGPR strains hold promise as biofertilizers for improving cereal productivity under water-deficit conditions.

Plant Growth-Promoting Rhizobacteria: A Promising Strategy To Optimize The Development Of Schizolobium Parahyba

Objective: To investigate the efficacy of plant growth-promoting rhizobacteria (PGPR) in enhancing the early development stages of Schizolobium parahyba, a critical species for the timber industry, aiming to optimize reforestation and agroforestry practices for sustainable forestry. Theoretical Framework: The research is grounded in the exploration of symbiotic relationships between PGPR strains and plant species, focusing on their potential to improve seed germination, plant growth, and biomass production. The study examines how these interactions can be leveraged to enhance agricultural productivity and sustainability, with a specific emphasis on the benefits of employing PGPR in forestry. Method: The study utilized an experimental approach, assessing the impact of four PGPR strains (Serratia marcescens, Pseudomonas protegens, Enterobacter absuriae, and Acinetobacter calcoaceticus) on S. parahyba seedlings. These were cultivated in three different substrates, with variables such as germination rate, above-ground and root growth, and biomass production meticulously measured to evaluate the effects of bacterial inoculation. Results and Conclusions: The application of PGPR notably improved all measured growth parameters in S. parahyba seedlings, with A. calcoaceticus and P. protegens specifically enhancing stem and root development, respectively. A synergistic effect was observed in substrates containing peat, underscoring the significant potential of PGPR in boosting the productivity and sustainability of early-stage forestry cultivation. The findings advocate for further field studies to fine-tune these interactions, aiming to establish more resilient and ecologically sustainable agricultural practices. Originality/Value: This research contributes novel insights into the utilization of PGPR in forestry, highlighting its substantial promise in enhancing the early growth stages of Schizolobium parahyba. By demonstrating the specific benefits of PGPR strains and their interactions with different substrates, the study offers a promising strategy for improving the sustainability and productivity of reforestation and agroforestry efforts.

Paenibacillus lentimorbus alleviates nutrient deficiency-induced stress in Zea mays by modulating root system architecture, auxin signaling, and metabolic pathways.

Paenibacillus lentimorbus reprograms auxin signaling and metabolic pathways for modulating root system architecture to mitigate nutrient deficiency in maize crops. The arable land across the world is having deficiency and disproportionate nutrients, limiting crop productivity. In this study, the potential of plant growth-promoting rhizobacteria (PGPR) viz., Pseudomonas putida, Paenibacillus lentimorbus, and their consortium was explored for growth promotion in maize (Zea mays) under nutrient-deficient conditions. PGPR inoculation improved the overall health of plants under nutrient-deficient conditions. The PGPR inoculation significantly improved the root system architecture and also induced changes in root cortical aerenchyma. Based on plant growth and physiological parameters inoculation with P. lentimorbus performed better as compared to P. putida, consortium, and uninoculated control. Furthermore, expression of auxin signaling (rum1, rul1, lrp1, rtcs, rtcl) and root hair development (rth)-related genes modulated the root development process to improve nutrient acquisition and tolerance to nutrient-deficient conditions in P. lentimorbus inoculated maize plants. Further, GC-MS analysis indicated the involvement of metabolites including carbohydrates and organic acids due to the interaction between maize roots and P. lentimorbus under nutrient-deficient conditions. These findings affirm that P. lentimorbus enhance overall plant growth by modulating the root system of maize to provide better tolerance to nutrient-deficient condition.

Evaluation of antifungal activity against Corynespora cassiicola by bacteria isolated from soil in the root zone of cucumber plants

Abstract. Duy LQ. 2023. Evaluation of antifungal activity against Corynespora cassiicola by bacteria isolated from soil in the root zone of cucumber plants. Biodiversitas 24: 6584-6591. Target leaf spot caused by Corynespora cassiicola poses a major disease threat to cucumber cultivation worldwide. Reliance on chemical fungicides has raised resistance to environmental and health concerns. As cucumber production expands globally, sustainable solutions are needed. Plant Growth-Promoting Rhizobacteria (PGPR) show promise but remain underexplored against C. cassiicola in cucumber. This study aimed to assess the potency of rhizobacteria in antagonistic activity against C. cassiicola, causing cucumber target leaf spots under in vitro conditions. The present study isolated bacterial strains from cucumber soil rhizosphere and screened for antifungal activity against C. cassiicola using dual culture assays. Using quantitative assays, selected antagonistic strains were further assessed for key biocontrol traits, including ?-1,3-glucanase, chitinase, and siderophore production. Cell-free supernatants were tested for direct fungal growth inhibition using the environmental toxicity. Isolated PGPR strains showed robust C. cassiicola inhibition from 39.8% to 62.6% growth reduction. Most antagonistic isolates produced ?-1,3-glucanase, chitinase, and siderophores and suppressed pathogen growth via metabolites in their supernatants. These results demonstrate multiple biocontrol mechanisms, including enzymatic degradation of fungal cell walls, iron competition through siderophores, and antimicrobial compound secretion. Bacillus siamensis strain TV16 exhibited the strongest overall antagonism against C. cassiicola. These findings reveal the biocontrol potential of PGPR for managing cucumber-target leaf-spot disease, offering a sustainable alternative to chemical pesticides. With further optimization and field testing, PGPR-based biopesticides can be integrated into cucumber production to improve crop health while reducing fungicide reliance.

Application of rhizobacteria to improve microbial community structure and maize (Zea mays L.) growth in saline soil.

The utilization of plant growth-promoting rhizobacteria (PGPR) has emerged as a prominent focus in contemporary research on soil microbiology, microecology, and plant stress tolerance. However, how PGPR influence the soil bacterial community and related ecological functions remains unclear. The aim of this study was to investigate the effects of three natural PGPR inoculations (YL07, Planococcus soli WZYH02; YL10, Bacillus atrophaeus WZYH01; YL0710, Planococcus soli WZYH02 and Bacillus atrophaeus WZYH01) on maize (Zea mays L.) growth under two salt stress conditions (S1, ECe = 2.1 ~ 2.5 dS/m; S2, ECe = 5.5 ~ 5.9 dS/m). The results revealed that compared to the control (CK), the average plant height of maize seedlings significantly increased by 27%, 23%, and 29% with YL07, YL10, and YL0710 inoculation under S1 conditions, respectively, and increased by 30%, 20%, and 18% under S2 conditions, respectively. Moreover, PGPR inoculation positively influenced the content of superoxide dismutase, catalase, soluble sugar, and proline in maize under salt stress. Subsequent analysis of alpha diversity indices, relative microbial abundance, principal coordinate analysis, cladograms, and linear discriminant analysis effect size histograms indicated significant alterations in the rhizosphere microbial community due to PGPR inoculation. FAPROTAX analysis demonstrated that YL10 inoculation in S2 rhizosphere soil had a notable impact on carbon cycle functions, specifically chemoheterotrophy, fermentation, and phototrophy. Thus, this study provides evidence that PGPR inoculation improves soil microbial communities and plant indices under salt stress. These findings shed light on the potential of PGPR as a viable approach for enhancing plant stress tolerance and fostering sustainable agricultural practices.

Exploring soybean cultivar susceptibility to sudden death syndrome: Insights into isoflavone responses and biocontrol potential

Sudden Death Syndrome (SDS) caused by Fusarium tucumaniae is a significant threat to soybean production in Argentina. This study assessed the susceptibility of SY 3 × 7 and SPS 4 × 4 soybeans cultivars to F. tucumaniae and studied changes in root isoflavone levels after infection. Additionally, the biocontrol potential of plant-growth promoting rhizobacteria (PGPR) against SDS was also examined. Our results demonstrated that the SY 3 × 7 cultivar exhibited higher disease severity and total fresh weight loss than SPS 4 × 4. Both cultivars showed induction of daidzein, glycitein, and genistein in response to infection, with the partially resistant cultivar displaying significantly higher daidzein levels than the susceptible cultivar at 14 days post infection (dpi) (2.74 vs 2.17-fold), declining to a lesser extent at 23 dpi (0.94 vs 0.35-fold, respectively). However, daidzein was not able to inhibit F. tucumaniae growth in in vitro assays probably due to its conversion to an isoflavonoid phytoalexin which would ultimately be an effective fungal inhibitor. Furthermore, the PGPR bacterium Bacillus amyloliquefaciens BNM340 displayed antagonistic activity against F. tucumaniae and reduced SDS symptoms in infected plants. This study sheds light on the varying susceptibility of soybean cultivars to SDS, offers insights into isoflavone responses during infection, and demonstrates the potential of PGPR as a biocontrol strategy for SDS management, providing ways for disease control in soybean production.

An Innovative Approach for Biocontrol of Meloidogyne incognita in Ginger Using Potential Bacteria Isolated from Indian Himalayas.

The prevalence of Meloidogyne incognita, a severe root-knot nematode, is alarmingly high in the production of ginger-a main cash crop of Himachal Pradesh, a Himalayan state of India. In order to control this through natural means, the nematicidal potential of plant growth-promoting rhizobacteria (PGPR) against M. incognita was analyzed. This is an effective alternative solution to manage nematode incidence as compared to hazardous chemicals under protected and field cultivation of ginger. In the present study an attempt has been made to isolate, characterize, and identify potential rhizobacteria associated with ginger rhizosphere and endosphere. In total, 169 bacterial isolates were isolated from ginger (Zingiber officinale) rhizosphere and endosphere of 4 different sites of Sirmaur district, screened out for multifarious PGP traits showing positive results. The combined cluster analysis and 16S rRNA genotypic analysis of selected bacterial isolates revealed that Serratia marcescens FS-23, Pseudochrobacter sp. GS-15, Stonotrophomonas pavanii HER-9, Pseudomonas brassicacearum HER-20 and Serratia marcescens IS-2 exhibited highest PGP traits. All tested bacterial isolates were capable of exerting a significant effect on mortality of juvenile M. incognita ranging upto 40-90% in laboratory experiments. Further a consortium of these screened isolates showed 86.67% reduction in gall formation by M. incognita in lab conditions. The remarkable increase to 93.24% with 138.73q/ha with application of charcoal based bio-formulation of consortium without adding any chemical fertilizer was observed in field trials of Nohradhar of Sirmaur district. An alternative choice as a biocontrol agent as well as for PGP activities, the novel and most robust isolate Serratia marcescens IS-2 had revealed to have a variety of bioactive metabolic products with abilities against nematodes, bacteria, and fungi.

The Co-Application of PGPR and Biochar Enhances the Production Capacity of Continuous Cropping Peppers in the Karst Yellow Soil Region of Southwest China

In recent years, a significant impediment to the advancement of China’s agricultural sector is the noteworthy challenge posed by diminished crop yields and quality due to ongoing continuous cropping obstacles. Numerous studies have consistently showcased the potential of plant growth-promoting rhizobacteria (PGPR) and biochar in augmenting the alleviation of continuous cropping barriers. Nevertheless, the potential of PGPR and biochar to remediate and improve continuous cropping peppers in the karst yellow soil area remains unclear. A 2-year field experiment was implemented to examine the impact of PGPR and biochar, when applied alone or in combination, on the production potential of continuous cropping peppers. The results revealed that PGPR and biochar significantly elevated the yield of fresh and dry pepper compared with TF treatment. The utilization of PGPR and biochar resulted in an augmentation of free amino acids, soluble sugar, and vitamin C content in pepper fruits, but a reduction in the nitrate content, which proved advantageous in enhancing the overall quality of peppers. Furthermore, the use of PGPR and biochar demonstrated significant benefits in enhancing NPK accumulation, fertilizer utilization, and economic efficiency. Nevertheless, the co-application of PGPR and biochar yielded significantly better results compared to their individual application. In conclusion, the utilization of PGPR and biochar demonstrated a favorable impact on the productivity and economic benefits of continuous cropping peppers. The simultaneous application of PGPR and biochar represents a promising approach to enhancing yield and improving the quality of peppers in the karst yellow soil region of Southwest China.

Selective extraction and preconcentration of melatonin mediated by hydrophobic natural deep eutectic systems

BackgroundSample preparation is the key to achieve the goals of Green Chemistry and represents the highest source of the total negative impact of analytical methodologies on the environment. Therefore, assessing the greenness of analytical procedures and, if possible, reducing their impact on the environment and workers is necessary. In this sense, the alternative analytical techniques must be cost-effective, eco-friendly, and sustainable, to focus these issues and ensure efficient extraction, preconcentration, and analysis of the targeted compounds. ResultsThe selective extraction and preconcentration of melatonin (MEL) mediated by hydrophobic natural deep eutectic systems (HPB-NADES) from three native plant growth-promoting rhizobacteria (PGPR) cultures was studied and performed. The HPB-NADES based on menthol:thymol showed excellent selectivity for MEL, evaluated through the 3-indole acetic acid and tryptophan recovery and the matrix effect values. The extraction recovery of MEL was 97.9 to 100.3%, with an RSD of less than 3% and an interesting enrichment factor of 14.7–15.2. Finally, the LOD and LOQ for MEL were 23.4 and 71.4 ng/L, with a linear range of 71.4–5000 ng/L showing good linearity (F less than 1.16). The sustainability of the methodology showed scores of 0.71 and 0.66, and a chemical risk corresponding to the use of 0.812 g of chloroform per extracted and analyzed sample. ConclusionsThe present study introduced, for the first time, a green analytical method for selectively extracting and quantifying MEL from three PGPR cultures using HPB-NADES. The methodology exhibited favorable linearity, LOD, LOQ, and extraction recoveries with negligible matrix effects. The use of environmentally friendly solvents and sample preparation techniques ensures the sustainability of the approach. Additionally, the present work highlighted the potential of PGPR in improving plant adaptation to abiotic stress under low MEL concentrations.

Utility of Plant Growth-Promoting Rhizobacteria for Sustainable Production of Bermudagrass Forage.

A two-year study was conducted in bermudagrass hay fields in central Alabama to estimate the potential of plant growth-promoting rhizobacteria (PGPR) as a tool for sustainable agriculture in forage management. This study compared the effects of two treatments of PGPR, applied with and without lowered rates of nitrogen, to a full rate of nitrogen fertilizer in a hay production system. The PGPR treatments included a single-strain treatment of Paenibacillus riograndensis (DH44), and a blend including two Bacillus pumilus strains (AP7 and AP18) and a strain of Bacillus sphaericus (AP282). Data collection included estimates of forage biomass, forage quality, insect populations, soil mesofauna populations, and soil microbial respiration. Applications of PGPR with a half rate of fertilizer yielded similar forage biomass and quality results as that of a full rate of nitrogen. All PGPR treatments increased soil microbial respiration over time. Additionally, treatments containing Paenibacillus riograndensis positively influenced soil mesofauna populations. The results of this study indicated promising potential for PGPR applied with lowered nitrogen rates to reduce chemical inputs while maintaining yield and quality of forage.

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.

Plant Growth-Promoting Rhizobacteria (PGPR): A Rampart against the Adverse Effects of Drought Stress

Abiotic stress significantly limits plant growth and production. Drought, in particular, is a severe constraint that affects growth and limits agricultural productivity on a global scale. Water stress induces in plants a set of morpho-anatomical (modification of root and leaf structure), physiological, and biochemical (relative water content, membrane stability, photosynthesis, hormonal balance, antioxidant systems, and osmolyte accumulation) changes mainly employed to cope with the drought stress. These strategies allow the plant to overcome the unfavorable period of limited water availability. Currently, a promising alternative is available to improve plant growth and tolerance under drought conditions. The use of osmotolerant plant growth-promoting rhizobacteria (PGPR) as inoculants can alleviate water stress by increasing the water use efficiency of the plant. The PGPR improve the tolerance of plants to drought, through changes in the morphology and architecture of the root system, production of phytohormones, extracellular polysaccharides, ACC 1-(aminocyclopropane-1-carboxylate) deaminase, volatile chemicals, and osmolyte accumulation. They may also enhance the antioxidant defense system and induce transcriptional regulation of stress response genes. This review addresses the effects of stress on plant growth, adaptation, and response to drought conditions and discusses the significant potential of PGPR to modulate the physiological response against water scarcity, ensuring plant survival and improving the resistance and growth of agricultural crops.

Potential of plant growth-promoting rhizobacteria to improve crop productivity and adaptation to a changing climate

Abstract Abiotic and biotic stresses negatively affect the growth and yield of crops worldwide. It is estimated that abiotic and biotic stresses account for global food crop losses of 50% and 30%, respectively. With the rapidly growing world population expected to reach 10 billion by 2050, the issue of food security is becoming a global concern. Climate change, which has its roots in industrialization, urbanization, and agricultural activities, further exacerbates food crop losses. Various innovative agricultural technologies, such as stress-tolerant varieties, smart irrigation systems, and shifting cropping calendars, have been used to both increase crop productivity and mitigate the effects of various stresses, but most of these strategies are time-intensive and costly. Therefore, strategies that are both sustainable and environmentally friendly, as well as economical, are required to face the challenge of providing the world’s human population with adequate food. In this context, plant growth-promoting rhizobacteria (PGPR) have the potential to increase crop productivity by mitigating the effects of various abiotic and biotic stresses associated with climate change. This approach can also improve the sustainability of agroecosystems by reducing the use of unsustainable agrochemicals, which contribute to greenhouse gas emissions. This review presents current information on how PGPR can mitigate the impacts of abiotic and biotic stresses, associated with climate change, food security, as well as the mechanisms underlying PGPR-induced tolerance to these stresses.

Nematicidal potential of plant growth-promoting rhizobacteria against Meloidogyne incognita infesting tomato under protected cultivation

BackgroundIn the protected cultivation of tomato (Solanum lycopersicum L.) crop, the severity of root-knot nematode, Meloidogyne incognita, incidence is alarming nowadays. To combat this, growers usually prefer using synthetic chemical pesticides, which in turn results in harming non-target beneficial microbes present in the soil micro-flora and indirectly toxic to human health. Therefore, attempts were made to find out the nematicidal potential of plant growth-promoting rhizobacteria (PGPR) against M. incognita, which could be used as an alternative solution to manage M. incognita incidence under protected cultivation.ResultsNematicidal potential of three PGPR isolates and their consortium against M. incognita under laboratory, pots, and field experiments was studied. Juvenile mortality of 91.67% was recorded at 100% consortium, followed by 73.33–81.33% by individual isolates. Similarly, hatching inhibition of 84.26% was recorded at 100% PGPR consortium followed by 78.48–83.21% in individual isolates after 96 h. of incubation. In the pots’ study, soil drenched with PGPR isolates consortium, followed by Bacillus subtilis DTBS 5, Pantoea agglomerans, and Bacillus amyloliquefaciens DSBA 11 recorded significant reductions in the nematode incidence. Whereas in the field study, PGPR isolates applied as soil drenching also significantly reduced nematode’s incidence in consortium, followed by B. subtilis DTBS 5 and B. amyloliquefaciens DSBA 11-treated soil in both field experiments. On an average, the plant growth promotion and fruit yield were enhanced than untreated control and PGPR isolates applied as soil drenching gave a significant result than bare root dip treatment.ConclusionsPGPR isolates, B. amyloliquefaciens DSBA 11, B. subtilis DTBS 5, and P. agglomerans, were found to be effective against M. incognita. This finding can be incorporated into the nematode management strategy in tomato crop grown under protected cultivation. Further to enhance the biocontrol efficacy of these PGPR isolates, suitable formulations of either individual or consortium need to be done.

Characterization and Potential of Plant Growth-Promoting Rhizobacteria (PGPR) Isolates Capacity Correlating with Their Hydrocarbon Biodegradation Capability

The aim of this research is to find the characteristics of three PGPR isolates—Azospirillum sp., Bacillus sp., and Pseudomonas sp.: First, by profiling their characteristics in a liquid bioremediation system and secondly by measuring their performance as a bioagent in a soil phytoremediation system using ramie plant (Boehmia niviea L.). A Randomized Block Design in triplicate is used: (1) a Nitrogenfree medium with mineral media containing 1% (wt/v) petroleum hydrocarbons; and (2) 1% (wt/v) glucose medium as control. We tested their petroleum-degrading capacity, nitrogenase activity, phytohormones production, and ramie plant growth. The results showed that both Pseudomonas sp. (98.7%, 81.78% degradation efficiency) and Azospirillum sp. (93.80%, 83.70%) were the superior candidate in both systems. They both show reduced but adequate phytohormone production, managing to improve ramie plant growth. Both also showed reduced but sufficient nitrogen fixing capabilities to improve hydrocarbon degradation activity effectively. Meanwhile, Bacillus sp. has the lowest biodegradation capabilities (84.07%; 78.6%) and lowest nitrogenase activity, while failing to improve plant growth. Therefore Bacillus sp. would be more beneficial in a bacterial consortium where its characteristics (high IAA production) can be coupled with other isolates that can offset its lack of phytohormone or nitrogenase activity.

Biocontrol potential of plant growth-promoting rhizobacteria (PGPR) against Sclerotiorum rolfsii diseases on sugar beet (Beta vulgaris L.)

A total of 49 bacterial isolates were collected from the sugar beet rhizosphere in two regions of Morocco (Kenitra and Meknes). These bacteria were tested for their inhibitory activity against Sclerotium rolfsii Sacc., the causative pathogen of damping-off and root rot of sugar beet. Ten isolates showed a high ability to inhibit the mycelial growth of the pathogenic fungus in dual culture bioassays. The molecular identification based on 16S ribosomal DNA gene revealed that these isolates belong to the Bacillus genus. In addition, these bacterial isolates have also been characterized in terms of the production of certain antifungal products as well as for their capacities as plant growth-promoting traits. Under greenhouse conditions, sugar beet seeds treated with the each bacterium showed significant reduction in damping-off disease. Plants from treated seeds showed significant increases in both the length of shoots and roots, and the plant fresh and dry weight. Iinterestingly, these selected bacterial isolates displayed high antagonistic activity against S. rolfsii, and significantly reduced the severity and incidence of root rot disease. Therefore, these results highlighted that the soil harbors antagonistic bacteria offering several plant growth-promoting (PGP) traits, which can be exploited as a powerful growth promoter and/or biological control agent in sugar beet plants.