Group Of Plant Growth Promoting Rhizobacteria Research Articles

Importance of Lactic Acid Bacteria as an Emerging Group of Plant Growth-Promoting Rhizobacteria in Sustainable Agroecosystems

Increasing awareness of the problems caused by synthetic agrochemicals, such as chemical fertilizers, pesticides, and herbicides, makes it crucial to discover substitute approaches that can guarantee competitive plant production and protect the environment while maintaining the natural balance in agroecosystems. One of the leading alternatives is utilizing rhizobacterial strains named plant growth-promoting rhizobacteria (PGPR). The utilization of PGPR-based biofertilizers for advancement in the sustainability of farming productions has received considerable critical attention all over the world because of their contribution to not only improving plant growth but also inducing biotic and abiotic stress tolerance. This review updates the aforementioned eco-friendly strategy in sustainable agroecosystems and provides new insights into the phytostimulation and bioprotection ability of lactic acid bacteria (LAB), an emerging taxon of PGPR. In this regard, the ability of LAB to synthesize metabolites, including organic acids, phenolic acids and their flavonoid derivatives, phytohormones, and antimicrobial substrates, is presented. The use of LAB provides a bridge between PGPR and environmentally friendly crop productivity, which can lead to sustainable production systems by reducing the use of agrochemicals, improving soil quality, and minimizing environmental pollution. All the beneficial aspects of LAB need to be addressed by future research to plan systematic methodologies for their use and/or to combine the use of PGPR along with other organic or inorganic inputs in sustainable production systems.

A novel PGPR strain, Streptomyces lasalocidi JCM 3373T, alleviates salt stress and shapes root architecture in soybean by secreting indole-3-carboxaldehyde.

While soybean (Glycine max L.) provides the most important source of vegetable oil and protein, it is sensitive to salinity, which seriously endangers the yield and quality during soybean production. The application of Plant Growth-Promoting Rhizobacteria (PGPR) to improve salt tolerance for plant is currently gaining increasing attention. Streptomycetes are a major group of PGPR. However, to date, few streptomycetes has been successfully developed and applied to promote salt tolerance in soybean. Here, we discovered a novel PGPR strain, Streptomyces lasalocidi JCM 3373T, from 36 strains of streptomycetes via assays of their capacity to alleviate salt stress in soybean. Microscopic observation showed that S. lasalocidi JCM 3373T does not colonise soybean roots. Chemical analysis confirmed that S. lasalocidi JCM 3373T secretes indole-3-carboxaldehyde (ICA1d). Importantly, IAC1d inoculation alleviates salt stress in soybean and modulates its root architecture by regulating the expression of stress-responsive genes GmVSP, GmPHD2 and GmWRKY54 and root growth-related genes GmPIN1a, GmPIN2a, GmYUCCA5 and GmYUCCA6. Taken together, the novel PGPR strain, S. lasalocidi JCM 3373T, alleviates salt stress and improves root architecture in soybean by secreting ICA1d. Our findings provide novel clues for the development of new microbial inoculant and the improvement of crop productivity under salt stress.

Effect of phosphate solubilizing and nitrogen-fixing bacteria on Pontianak siam citrus (Citrus ×nobilis var. microcarpa) seed germination

Abstract. Adhyaningtyas RFI, Rahmawati, Mukarlina. 2023. Effect of phosphate solubilizing and nitrogen-fixing bacteria on Pontianak siam citrus (Citrus ×nobilis var. microcarpa) seed germination. Nusantara Bioscience 15: 245-250. West Kalimantan is one of Indonesia's largest producing areas for Siam citrus (Citrus ×nobilis var. microcarpa Hassk.). It is necessary to carry out the proper treatments within the early stages of planting, which increases the speed of germination of citrus seeds to quickly increase the number of seedlings. The biological agents that play a role in promoting plant growth are a group of Plant Growth-Promoting Rhizobacteria (PGPR), consisting of Phosphate-Solubilizing Bacteria (PSB) and Nitrogen-Fixing Bacteria (NFB). This study aims to determine the effect of a combination treatment or a single treatment of phosphate-solubilizing and nitrogen-fixing bacteria, which is known to obtain the best results in the germination and growth of Siam citrus seeds. The study was conducted in a nonfactorial, Completely Randomized Design (CRD). The given treatments were control (without bacterial inoculum), nitrogen-fixing bacteria (NFB P1), phosphate solubilizing bacteria (PSB P2), a combination of NFB and PSB bacteria with a ratio of 1:1 (P3), a combination of NFB and PSB bacteria with a ratio of 2:1 (P4), and the combination of NFB and PSB bacteria with a ratio of 1:2 (P5). Observations were made for 4 weeks after planting. A single treatment with phosphate-solubilizing bacteria (P2) gave the best result on almost all parameters, such as germination percentage, emergence time of germination, root length, number of leaves and fresh weight of Siam citrus seedlings.

The PGPR Fertilizer Processing Training in Banyuresmi Village, Jiput District, Pandeglang Regency, Banten Province

The availability of organic fertilizer is one of the keys to the success of the go-organic program that is scheduled by the government. Increasing the use of organic fertilizers and reducing the use of pesticide fertilizers, it is expected to increase the yield of bamboo farming in Banyuresmi Village. Plant Growth Promoting Rhizobacteria (PGPR) fertilizer is one way to restore soil fertility because some bacteria from the PGPR group are nitrogen-fixing bacteria. Thus, it is necessary to socialize and assist the manufacture of PGPR fertilizer in Banyuresmi Village. The method of implementing this activity includes 1) the preparation stage, namely preparing a simple guide, and preparing tools and materials for the manufacture of mycorrhizal-PGPR combination. 2) the implementation stage consists of a) (Lecture/Counseling Method); b) Training for the manufacture of mycorrhizal-PGPR combinations; Discussion and question and answer; and Evaluation. This training concludes that the residents of Banyuresmi Village are greatly helped by the training in making PGPR fertilizer. Through the training, the residents of Bnyuresmi Village received information about processing PGPR fertilizer as a way to increase the production of bamboo plant commodities.

Maize growth response to different Bacillus strains isolated from a salt-marshland area under salinity stress

Maize (Zea mays) growth performance has been hindered due to the high soil salinity. Salinity is one of the most severe abiotic stresses that has led to growth imbalance and profitability of harvests in arid and semi-arid regions. Plants have taken advantage of salt-tolerant bacteria as plant growth-promoters to enhance growth and reduce the adverse effects of salinity through the regulation of some biochemical, physiological, and molecular features. Preferences for non-chemical, eco-friendly, and economical approaches have caused the inquiry of the Bacillus genus as a joint group of plant growth-promoting rhizobacteria known to alleviate salt-stress impacts. In the present study, halotolerant Bacillus strains were isolated from salt-marshland soil and characterized for their physiological, molecular, and biochemical properties. Twenty-four bacterial isolates collected from high saline fields of salt marshland were analyzed by MALDI-TOF MS proteome analysis, which confirmed the taxonomic affiliation with Bacillus cereus, Bacillus subtilis, Bacillus atrophaeus, and Bacillus thorngiensis. Applying the isolates on maize plants as bio-inoculant bacteria obviously increased the growth parameters (P < 0.01). Pot experiments showed that isolates 74 and 90 were the most prominent strains to minimize the harmful effects of salinity. Its effects are heightening the potassium/sodium ratio and K-Na selectivity in shoots and roots measured by flame atomic absorption photometry (AAS). Accordingly, Bacillus cereus isolate 74 showed a maximum increase in dry weights of the shoot (133.89%), root (237.08%), length of the shoot (125%), and root (119.44%) compared to the control condition. Our findings suggest that bacteria isolated from marshland may be an economical and simple means to increase plant growth and resistance to high salinity soil conditions.

Mechanism and application of Sesbania root-nodulating bacteria: an alternative for chemical fertilizers and sustainable development.

Chemical fertilizers are used in large-scale throughout the globe to satisfy the food and feed requirement of the world. Demanding cropping with the enhanced application of chemical fertilizers, linked with a decline in the recycling of natural or other waste materials, has led to a decrease in the organic carbon levels in soils, impaired soil physical properties and shrinking soil microbial biodiversity. Sustenance and improvement of soil fertility are fundamental for comprehensive food security and ecological sustainability. To feed the large-scale growing population, the role of biofertilizers and their study tends to be an essential aspect globally. In this review, we have emphasized the nitrogen-fixing plants of Sesbania species. It is a plant that is able to accumulate nitrogen-rich biomass and used as a green manure, which help in soil amelioration. Problems of soil infertility due to salinity, alkalinity and waterlogging could be alleviated through the use of biologically fixed nitrogen by Sesbania plants leading to the conversion of futile land into a fertile one. A group of plant growth-promoting rhizobacteria termed as "rhizobia" are able to nodulate a variety of legumes including Sesbania. The host-specific rhizobial strains can be used as potential alternative for nitrogenous fertilizers as they help the host plant in growth and development and enhance their endurance under stressed conditions. The review gives the depth understanding of how the agriculturally important microorganisms can be used for the reduction of broad-scale application of chemical fertilizers with special attention to Sesbania-nodulating rhizobia.

The fabrication of the complex bio-fertilizer for wheat cultivation based on collection bacteria of the PGPR group

Abstract. Aipova R, Abdykadyrova A, Silayev D, Tazabekova E, Oshergina I, Ten E, Kurmanbaye A. 2020. The fabrication of the complex bio-fertilizer for wheat cultivation based on collection bacteria of the PGPR group. Biodiversitas 21: 5021-5028. The development of new types of biological products based on microbial complexes from local bacterial strains is a great theoretical and practical interest for agriculture. It can provide an opportunity for better preservation of the natural properties of the wheat products under extreme conditions. The aim of this study was to obtain and test a biological product to increase wheat productivity in northern Kazakhstan. Our data indicate the potential of Plant Growth-Promoting Rhizobacteria (PGPR) group bacteria for the development of biofertilizers and biopesticides. For instance, the bacteria B. mojavensis showed effectiveness in the experiments with the wheat (Astana-2 type). We observed an increase in wheat yield by 15% under conditions of artificial infection of crops with snow mold (by 2.5fold compared with the control). The results demonstrated that the B. mojavensis Lhv 97 strain can be used as an ingredient of biological products due to its activity against plant diseases caused by phytopathogenic fungi.

Enhancement of salinity stress tolerance and plant growth in finger millet using fluorescent pseudomonads

Soil salinity, the most critical environmental stress hampering crop productivity in drier agro-ecosystems, is mitigated through various management strategies. A preference for a non-chemical, eco-friendly, and economical approach has led to the investigation of fluorescent pseudomonads, a common group of plant growth-promoting rhizobacteria (PGPR), known to alleviate stress. In the present study, salinity-sensitive finger millet (Indaf-9) seeds treated with 40 fluorescent pseudomonad isolates were obtained from different saline regions of India. From these, 20 were selected based on growth promotion studies. These isolates were again subjected to growth promotion studies but under varied saline concentrations (0–350 mM NaCl). The results obtained were validated with studies on growth kinetics under a gradient of NaCl concentrations. Three strains, SPF-5, SPF-33, SPF-37, were selected based on their performance and characterized. They were screened for their plant growth-promoting traits (indole acetic acid, biofilm, siderophore, and ACC deaminase), stress-related physiological traits (enzymatic antioxidants, free proline, H2O2, lipid peroxidation, total protein, phenolics, flavonoids, total chlorophyll, leaf relative water content, and dry weight) and growth parameters under green-house conditions. Under increased salinity stress, strain SPF-33 showed increased activity of enzymatic antioxidants and elevation in proline content along with decreased lipid peroxidation and H2O2, with increased plant height and number of spikelets. Similarly, treatment with SPF-37 exhibited a significant increase in germination, vigor index, increased plant height, and the number of spikelets, total chlorophyll, phenolics, flavonoids, proteins, and leaf relative water content under 350 mM NaCl as compared to the control. Overall, our results indicate the fluorescent Pseudomonad strains SPF-33 and SPF-37 are strong candidates for alleviating salt stress in the field.

Molecular Characterization of Rhizobacteria (Isolate EO-4) as Potential Solvent of Phosphate in-vitro from the Mangrove Ecosystem of Teluk Awur, Jepara-Indonesia

Rejuvenation and conservation of mangrove ecosystems, especially the Teluk Awur mangrove ecosystem, Jepara Regency, can be done by using bacteria that are capable of supporting plant growth or called Plant Growth Promoting Rhizobacteria (PGPR). One of the mechanisms that support plant growth by the PGPR group is phosphate dissolving activity, because the phosphate in the soil is in the form of a compound that is difficult for plants to absorb. This study aims to determine the character of Rhizobacter isolates as a superior phosphate solvent in dissolving phosphates in-vitro from the Teluk Awur mangrove ecosystem, namely isolates coded EO-4. These isolates have similar microbiological and biochemical characters to the genus Enterobacter. Molecular characterization of isolates was carried out using the Polymerase Chain Reaction (PCR) method - 16S rRNA sequence analysis (comparing with 16S rRNA sequences in gene banks). The results showed that the phosphate-solubilizing rhizobacteria that were isolated had the same base pair percentage of 48% with Enterobacter pyrinus (access number NR_028875).

Metatranscriptomics and nitrogen fixation from the rhizoplane of maize plantlets inoculated with a group of PGPRs

Plant roots are inhabited by a large diversity of microbes, some of which are beneficial for the growth of plants and known as plant growth promoting rhizobacteria (PGPR). In this work, we designed a multispecies inoculum of PGPRs containing Rhizobium phaseoli, Sinorhizobium americanum and Azospirillum brasilense nitrogen-fixing strains and other plant-growth promoting bacteria such as Bacillus amyloliquefaciens and Methylobacterium extorquens. We evaluated the effect of this group of bacteria on the growth of one-month-old maize plants. The multispecies inoculum exerted a beneficial effect on maize plants that was greater than that obtained with single-bacteria. Using the same multispecies inoculant, acetylene reduction was recorded in 5-day-old roots indicating active nitrogen fixation by bacteria in maize. Azospirillum nitrogen fixation was lower than that obtained with the multispecies inoculum. We focused on the analysis of R. phaseoli gene expression in presence of other PGPRs. Many R. phaseoli up- regulated genes in roots in the presence of other bacteria are hypothetical, showing our poor knowledge of bacteria-bacteria interactions. Other genes indicated bacterial nutrient competition and R. phaseoli stress. Differentially expressed transcriptional regulators were identified that may be key in bacteria-bacteria interaction regulation. Additionally, gene expression was analyzed from Azospirillum but not from sinorhizobia and methylobacteria due to the low number of transcripts obtained from maize roots. The metatranscriptomic analysis from maize roots showed expression of Azospirillum nif genes in the presence of PGPR bacteria. Our hypothesis is that other bacteria stimulate Azospirillum capacity to fix nitrogen and this should be further explored.

Plant Growth Promoting Activity of Actinomycetes Isolated from Soybean Rhizosphere

Plant Growth Promoting Rhizobacteria (PGPR) is considered as the biological agent for improving plant growth. One Group of PGPR that have an important role in growth promoting of plant is Actinomycetes. The objective of this study was to isolate and screen Actinomycetes isolated from soybean rhizosphere as growth promoter of soybean in vitro. Fifty-three Actinomycetes isolates have successfully been isolated from soybean rhizosphere using two media, mainly Humic acid Vitamin Agar (HVA) and starch casein agar (SCA). Among 53 isolates, 18 (34%) isolates were able to produce IAA in range of 2.08 ppm to 16.70 ppm. Growth promotion test of soybean in vitro using Ragdoll method resulted 7 Actinomycetes isolates that significantly enhanced 3 plant growth parameters, including hypocotyl and radicular length as well as the number of lateral roots. Of those 7 isolates of Actinomycetes, 5 isolates were able to grow on nitrogen-free medium and solubilize phosphate. Those 5 isolates also were found as non-pathogenic, based on the negative reaction in hypersensitivity test. Based on 16S rRNA sequence analysis, 5 selected Actinomycetes isolates were highly homolog with Streptomyces genera in different taxa of species and strains (similarity ≥99%). Our finding reveals a potent application of 5 Actinomycetes isolates as plant growth promoter in soybean agriculture.

Characterizations of endophytic Bacillus strains from tomato roots as growth promoter and biocontrol of Ralstonia solanacearum

Yanti Y, Warnita, Reflin, Nasution CR. 2018. Characterizations of endophytic Bacillus strains from tomato roots as growth promoter and biocontrol of Ralstonia solanacearum. Biodiversitas 19: 906-911. Bacterial wilt caused by Ralstonia solanacearum is the most damaging vascular pathogens in tomato and many other crops in tropical, subtropical and warm temperate areas of the world limiting its production. Biological agents such as Plant growth Promoting Rhizobacteria (PGPR) is considered as a potential biological control agent for the suppression of plant diseases such as bacterial wilt. Bacillus spp. are one of the most potential genera of PGPR group used for controlling pathogens and promoting plant growth because of their spore-forming ability which increases their adaptation to the environment. The aims of the research were to isolate Endophytic Bacillus isolates, to characterize its ability as plant growth promoter and pathogen controller, and to identify its molecular genetic using 16S rRNA. Bacillus strains were isolated from healthy tomato roots. All Bacillus spp. strains acquired from isolation were then screened directly on plants in completely randomized design experiments with 3 replications. All potential strains were screened and identified using 16S rRNA with 27F and 1492R primers. Results showed that out of 15 obtained isolates, 6 of them showed a good ability to both promote growth and control R. solanacearum. All isolates were identified as B. Pseudomycoides strain NBRC 101232, B. cereus strain CCM 2010, B. toyonensis strain BCT-7112, B. anthracis strain ATCC 14578, B. cereus strain JCM 2152 and B. cereus ATCC 14579.

PheS * , an effective host-genotype-independent counter-selectable marker for marker-free chromosome deletion in Bacillus amyloliquefaciens.

Aside from applications in the production of commercial enzymes and metabolites, Bacillus amyloliquefaciens is also an important group of plant growth-promoting rhizobacteria that supports plant growth and suppresses phytopathogens. A host-genotype-independent counter-selectable marker would enable rapid genetic manipulation and metabolic engineering, accelerating the study of B. amyloliquefaciens and its development as both a microbial cell factory and plant growth-promoting rhizobacteria. Here, a host-genotype-independent counter-selectable marker pheS * was constructed through a point mutation of the gene pheS, which encodes the α-subunit of phenylalanyl-tRNA synthetase in Bacillus subtilis strain 168. In the presence of 5mM p-chloro-phenylalanine, 100% of B. amyloliquefaciens strain SQR9 cells carrying pheS * were killed, whereas the wild-type strain SQR9 showed resistance to p-chloro-phenylalanine. A simple pheS * and overlap-PCR-based strategy was developed to create the marker-free deletion of the amyE gene as well as a 37-kb bmy cluster in B. amyloliquefaciens SQR9. The effectiveness of pheS * as a counter-selectable marker in B. amyloliquefaciens was further confirmed through the deletion of amyE genes in strains B. amyloliquefaciens FZB42 and NJN-6. In addition, the potential use of pheS * in other Bacillus species was preliminarily assessed. The expression of PheS* in B. subtilis strain 168 and B. cereus strain ATCC 14579 caused pronounced sensitivity of both hosts to p-chloro-phenylalanine, indicating that pheS * could be used as a counter-selectable marker (CSM) in these strains.

In vitroevaluation of plant growth regulators on tissue culture bioassay produced byPseudomonasspecies

Fluorescent Pseudomonas sp. is emerging as largest and potentially most promising group of PGPR (plant growth promoting rhizobacteria) that are involved in plant growth enhancement. Plant growth regulators viz., auxins, cytokinins and gibberellins help in plant growth and development. In present study, fluorescent Pseudomonas strains isolated from rhizospheric soil from temperate fruit zone of Himachal Pradesh were investigated for plant growth regulator production i.e. auxins, gibberellins and cytokinins in nutrient broth. All the strains tested produced plant growth regulators in concentrations auxins (1.83–21μg/ml), gibberellins (116.1–485.8μg/ml) and cytokinins (45.4–295.4μg/ml). Two strains (An-1-kul and An-13-kul) were selected on the basis of over all PGPR activities for production of growth regulators. Molecular characterization of best selected Pseudomonas strains were done by 16S-rRNA technique. Plant growth regulators produced by best isolates were further studied to observe their effect on growth of callus formation, shoot formation of broccoli and root elongation of cabbage

Isolation and characterization of rhizosphere auxin producing Bacilli and evaluation of their potency on wheat growth improvement

Enhancement of plant growth by Bacillus is well documented and several mechanisms have been suggested for the phytostimulatory activity of this group of plant growth-promoting rhizobacteria (PGPR). In the present work, the PGP potential of plant associated Bacillus spp. and their growth-promoting effect on wheat were studied. Six out of 35 strains were chosen based on seed germination assay, plant growth-promoting abilities, enzymatic function, and auxin production. All tested strains were subjected to pot experiments and their phenotypic and molecular assays were also done. Two Bacillus strains including WhIr-15 and WhIr-12 produce maximum amount of auxin (16.2 and 14 µg ml−1, respectively). Strain WhIr-15 had just the ability to produce indo-3-acetic acid (IAA), lipase, and protease enzymes. Strain WhIr-12 was also recorded positive for siderophore, auxin production, and phosphorus (P) solubilization. Bacterial IAA production positively correlated with root length (r = 0.875; p ≤ 0.05). Significant enhancement in root weight (71% and 53%) and in panicle weight (91% and 77%) was recorded in WhIr-15 and WhIr-12, respectively, over untreated controls. Based on phenotypic and 16S rDNA sequencing, these two strains belong to Bacillus sp. Based on our results, phytohormone-producing Bacillus sp. can be applied at field level to improve wheat productivity.