Plant Growth Promoting Rhizobacteria Consortium Research Articles

Expression of defense responsive genes in tripartite interaction of cucumber mosaic virus and plant growth promoting rhizobacteria in ridge gourd (Luffa acutangula (L.) Roxb)

The mosaic caused by cucumber mosaic virus (CMV) on ridge gourd (Luffa acutangula (L.) Roxb) is an important disease. An attempt was made to use a consortium of plant growth promoting rhizobacteria to manage the disease with an aim to reduce the usage of pesticide to control its vector. Eleven isolates of Bacillus spp. were selected based on their plant gowth promotion ability on ridge gourd cv. COH1. Among these, Bacillus pumilus (BSC 4), B. subtilis (Bbv 57) and B. subtilis (BST 8) had shown their potentiality in reducing the severity of CMV disease under artificial conditions. The compatibility test showed that these isolates were compatible to each other. A Bacillus consortium was prepared and evaluated for its efficacy against CMV on ridge gourd and the results showed a reduction of 49.98 % in disease severity over control. The quantitative gene expression analysis revealed that the defense genes viz., peroxidase, polyphenol oxidase, catalase and super oxide dismutase were upregulated in consortium treated ridge gourd plants. The upregulation of these genes indicated the activation of defense pathways which witnessed the induction of systemic resistance in Bacillus consortium treated plants. All gene expressions were reached its peak nearly two to three fold in the consortium treated plants except catalase, its peak expression was found in salicylic acid treated plants which served as a positive control. Correspondingly, the quantitative enzymatic analysis of these defense enzymes at different time intervals was also reflected in similar manner. The elevated level of defense enzymes in plant growth promoting rhizobacteria consortium treated plants was the evident for the onset of systemic resistance.

Volatile Organic Compounds (VOCs) Emission and Antioxidant Activities of Rice Treated with a Consortium of Plant Growth-Promoting Rhizobacteria under Drought Conditions

Volatile Organic Compounds (VOCs) Emission and Antioxidant Activities of Rice Treated with a Consortium of Plant Growth-Promoting Rhizobacteria under Drought Conditions

Synergistic effects of arbuscular mycorrhizal fungi associated to plant growth-promoting rhizobacteria in suppression of soil-borne Fusarium wilt of date palm

Soil-borne Fusarium wilt represents one of the major problems in the cultivation of the date palm. Arbuscular mycorrhizal fungi (AMF) consortium and plant growth-promoting rhizobacteria (PGPR) consortium were tested to determine the efficacy in disease management of Fusarium wilt. When applied individually, PGPR or AMF consortium reduced disease incidence, disease severity, and mortality rate of date palm seedlings. The combination of these consortia showed the best control efficiency which reflects a significant synergistic effect. The decrease in disease progression was accompanied by a significant promotion of plant immunity through the activation of the phenylpropanoid pathway, which was concreted by enhancement of PAL activity and accumulation of polyphenols and lignin content in date palm roots. In vitro antagonistic tests against Fusarium. oxysporum f. sp. albedinis (Foa) revealed that the bacterial strains of the PGPR consortium inhibited Foa growth, particularly the strain Bacillus cereus strain 263AG5' (60.59%). The evaluation of the mycorrhizal status of date palm roots after 27 weeks following the inoculation with Foa showed that the addition of both consortia was accompanied by a 3-fold increase in the intensity of mycorrhization and the arbuscules and vesicles number and 1.5 times increase in the frequency of mycorrhization. Our results highlight the high synergistic effect between PGPR and AMF consortia in date palm protection against Foa that could be attributed to the association of their antagonistic effect with their strong capacity for stimulation of plant natural defenses which suggests that these PGPR/AMF could be an effective approach to pathogen suppression.

Can arbuscular mycorrhizal fungi and rhizobacteria facilitate 33P uptake in maize plants under water stress?

Arbuscular mycorrhizal fungi (AMF) and plant growth-promoting rhizobacteria (PGPR) are able to provide key ecosystem services, protecting plants against biotic and abiotic stresses. Here, we hypothesized that a combination of AMF (Rhizophagus clarus) and PGPR (Bacillus sp.) could enhance 33P uptake in maize plants under soil water stress. A microcosm experiment using mesh exclusion and a radiolabeled phosphorus tracer (33P) was installed using three types of inoculation: i) only AMF, ii) only PGPR, and iii) a consortium of AMF and PGPR, alongside a control treatment without inoculation. For all treatments, a gradient of three water-holding capacities (WHC) was considered i) 30% (severe drought), ii) 50% (moderate drought), and iii) 80% (optimal condition, no water stress). In severe drought conditions, AMF root colonization of dual-inoculated plants was significantly lower compared to individual inoculation of the AMF, whilst 33P uptake by dual-inoculated plants or plants inoculated with bacteria was 2.4-fold greater than the uninoculated treatment. Under moderate drought conditions the use of AMF promoted the highest 33P uptake by plants, increasing it by 2.1-fold, when compared to the uninoculated treatment. Without drought stress, AMF showed the lowest 33P uptake and, overall, plant P acquisition was lower for all inoculation types when compared to the severe and moderate drought treatments. The total shoot P content was modulated by the water-holding capacity and inoculation type, with the lowest values observed under severe drought and the highest values under moderate drought. The highest soil electrical conductivity (EC) values were found under severe drought in AMF-inoculated plants and the lowest EC for no drought in single or dual-inoculated plants. Furthermore, water-holding capacity influenced the total soil bacterial and mycorrhizal abundance over time, with the highest abundances being found under severe and moderate drought. This study demonstrates that the positive influence of microbial inoculation on 33P uptake by plants varied with soil water gradient. Furthermore, under severe stress conditions, AMF invested more in the production of hyphae, vesicles and spore production, indicating a significant carbon drain from the host plant as evidenced by the lack of translation of increased 33P uptake into biomass. Therefore, under severe drought the use of bacteria or dual-inoculation seems to be more effective than individual AMF inoculation in terms of 33P uptake by plants, while under moderate drought, the use of AMF stood out.

Performance evaluation of native plant growth-promoting rhizobacteria for paddy yield enhancement in the jhum fields of Mokokchung, Nagaland, North East India

The present study was carried out to evaluate the performance of native plant growth-promoting rhizobacteria (PGPR) on jhum paddy yield enhancement in Nagaland, Northeast India. Three indigenous PGPR isolates (Bacillus cereus MKGB, Pseudomonas fluorescens MKGPf, and Azospirillum oryzae MKGAz) were tested in the soil microcosm and jhum fields of Longkhum and Ungma villages in Mokokchung, Nagaland. The maximum 78.44% seed germination, 165 cm plant height, 30 leaves, 5 tillers, and 5 panicles per plant were recorded in the PGPR consortium inoculated pot soil. Similarly, maximum 151 grains per panicle, 21.66 g grain yield per plant, and 33.50 g of straw biomass were recorded in the same treatment. The observations from the field trials revealed a maximum of 4.67 t ha−1 paddy yield in the Longkhum village jhum field inoculated with the PGPR consortium which was significantly different from the control (T1) at a p value of ≤0.05%. Similarly 4.74 t ha−1 paddy yield was obtained from the PGPR consortium applied jhum plots in Ungma village. The PGPR consortium was found more effective and promising than the single culture inoculation in paddy yield enhancement. The study suggests the application of tested PGPR consortium in jhum fields for soil health and crop productivity improvement and achieving agricultural sustainability as well as social prosperity in the rural areas of North East India.

Combating iron and zinc malnutrition through mineral biofortification in maize through plant growth promoting Bacillus and Paenibacillus species.

The burgeoning population of the world is causing food insecurity not only by less food availability but also by the malnutrition of essential nutrients and vitamins. Malnutrition is mostly linked with food having micronutrients lower than the optimal concentration of that specific food commodity and becoming an emerging challenge over the globe. Microbial biofortification in agriculture ensures nutritional security through microbial nitrogen fixation, and improved phosphate and zinc solubilization, which increase the uptake of these nutrients. The present study evaluates the novel plant growth-promoting rhizobacteria (PGPR) to biofortify maize gain. For this purpose, a pot and two field experiments for maize were conducted. PGPRs were applied alone and in combination for a better understanding of the biofortification potential of these strains. At physiological maturity, the growth parameters, and at harvest, the yield, microbial population, and nutritional status of maize were determined. Results revealed that the consortium (ZM27+ZM63+S10) has caused the maximum increase in growth under pot studies like plant height (31%), shoot fresh weight (28%), shoot dry weight (27%), root fresh (33%) and dry weights (29%), and microbial count (21%) in the maize rhizosphere. The mineral analysis of the pot trial also revealed that consortium of ZM27+ZM63+S10 has caused 28, 16, 20, 11 and 11% increases in P, N, K, Fe, and Zn contents in maize, respectively, as compared to un-inoculated treatment in pot studies. A similar trend of results was also observed in both field trials as the consortium of ZM27+ZM63+S10 caused the maximum increase in not only growth and biological properties but also caused maximum biofortification of mineral nutrients in maize grains. The grain yield and 1000-grain weight were also found significantly higher 17 and 12%, respectively, under consortium application as compared to control. So, it can be concluded from these significant results obtained from the PGPR consortium application that microbial inoculants play a significant role in enhancing the growth, yield, and quality of the maize. However, the extensive evaluation of the consortium may help in the formulation of a biofertilizer for sustainable production and biofortification of maize to cope with nutritional security.

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.

Plant growth-promoting rhizobacterial inoculation to improve growth, yield, and grain nutrient uptake of teff varieties.

Inoculation of plant growth-promoting rhizobacteria (PGPR) improves the growth, yield, and plant nutrient uptake, as well as rhizosphere fertility, without harming the environment and human health. This study aimed to examine the effect of either individual or consortium of PGP bacterial inoculation on the growth, yield, and grain nutrient uptake of teff varieties. Three potential PGPR strains (i.e., Pseudomonas fluorescens biotype G, Enterobacter cloacae ss disolvens, and Serratia marcescens ss marcescens) were used for this study. Field evaluation was carried out in RCBD with 5 treatments. Highly significant (P < 0.001) differences were observed among treatments for plant height (PH), panicle length (PL), number of the total spike (NTS), shoot dry weight (SDW), grain yield (GY), and straw yield (SY). There was also teff variety that significantly (P < 0.01) affects PL, SDW, and SY. However, the interaction effect of the two factors (treatment*variety) did not significantly influence teff agronomic traits and grain nutrient uptake. The highest PH (133.5 cm), PL (53.2), NTS (30.9), SDW (18.1 t/ha), SY (10.7 t/ha), and GY (2.7 t/ha) were observed on Dukem variety (Dz-01-974) inoculated with PGPR consortium. Wherein 2.2 fold increase was observed in grain yield per hectare over the control. Inoculation of PGPR consortium showed better performance in promoting plant growth, yield, and grain nutrient uptake of teff varieties compared with the individual PGP bacterial application, and PGPR consortium could be used as inoculants to enhance teff production and productivity.

Potential of plant growth promoting bacterial consortium for improving the growth and yield of wheat under saline conditions.

Owing to inconsistent results of a single bacterial strain, co-inoculation of more than one strain under salinity stress could be a more effective strategy to induce salt tolerance. Co-inoculation of more than one bacterial strain could be more effective due to the presence of several growths promoting traits. This study was conducted to evaluate the effectiveness of multi-strains bacterial consortium to promote wheat growth under salinity stress. Several plant growth promoting rhizobacteria (PGPR) had been isolated and tested for their ability to grow in increasing concentrations of sodium chloride (NaCl). Those rhizobacterial strains having tolerance against salinity were screened to evaluate their ability to promote wheat growth in the presence of salinity by conducting jar trials under axenic conditions. The rhizobacteria with promising results were tested for their compatibility with each other before developing multi-strain inoculum of PGPR. The compatible PGPR strains were characterized, and multi-strain inoculum was then evaluated for promoting wheat growth under axenic conditions at different salinity levels, i.e., 2.1 (normal soil), 6, 12, and 18 dS m–1. The most promising combination was further evaluated by conducting a pot trial in the greenhouse. The results showed that compared to a single rhizobacterial strain, better growth-promoting effect was observed when rhizobacterial strains were co-inoculated. The multi-strain consortium of PGPR caused a significant positive impact on shoot length, root length, shoot fresh weight, and root fresh weight of wheat at the highest salinity level in the jar as well as in the pot trial. Results showed that the multi-strain consortium of PGPR caused significant positive effects on the biochemical traits of wheat by decreasing electrolyte leakage and increasing chlorophyll contents, relative water contents (RWC), and K/Na ratio. It can be concluded that a multi-strain consortium of PGPR (Ensifer adhaerens strain BK-30, Pseudomonas fluorescens strain SN5, and Bacillus megaterium strain SN15) could be more effective to combat the salinity stress owing to the presence of a variety of growth-promoting traits. However, further work is going on to evaluate the efficacy of multi-strain inoculum of PGPR under salt-affected field conditions.

Phytoremediation of DEHP and heavy metals co-contaminated soil by rice assisted with a PGPR consortium: Insights into the regulation of ion homeostasis, improvement of photosynthesis and enrichment of beneficial bacteria in rhizosphere soil

The coexistence of di (2-ethylhexyl) phthalate (DEHP), Cd, and Zn poses a serious challenge to soil ecosystems. This study aimed to evaluate the phytoremediation potential of rice assisted with a plant growth promoting rhizobacteria (PGPR) consortium for the remediation of DEHP, Cd, and Zn co-contaminated soil. The consortium consisted of four bacterial strains, all of which exhibited Cd–Zn resistance and DEHP degradability. The results showed that the rice assisted by the bacterial consortium dissipated 86.1% DEHP while removing 76.0% Cd2+ and 92.2% Zn2+ from soil within 30 d. The presence of the PGPR consortium promoted plant growth and improved soil enzymatic activity, which may have helped enhance the removal of DEHP and heavy metals from the soil. Moreover, the application of the consortium modified the bacterial community and increased the relative abundance of bacteria related to DEHP degradation (Sphingomonas, Xanthobacteraceae), heavy metal immobilization (Massilia), and soil nutrient cycling (Nitrospira, Vicinamibacterales), which promoted plant growth and the removal of DEHP and heavy metals from soil. Notably, the DEHP and heavy metal contents in rice decreased substantially during the phytoremediation process. Therefore, the PGPR consortium could be beneficial for enhancing the removal of DEHP and heavy metals from the soil, without inducing the accumulation of these pollutants in rice. In general, this study confirmed that the combined use of rice and the PGPR consortium could remedy DEHP and heavy metal co-contaminated soil economically and ecologically without simultaneously posing risks for rice consumption.

Enhancing productivity of perennial aromatic grasses on marginal lands through plant growth promoting rhizobacteria

AbstractThe cultivation of perennial aromatic grasses on marginal lands is a socio‐economically and ecologically sustainable approach. However, the studies on assessment of the potential efficacies of consortium of plant growth promoting rhizobacteria (PGPR) in enhancing the productivity of perennial aromatic grasses on marginal lands are rare. In this study, therefore, we studied the effect of PGPR consortium (Pseudomonas protegens and two strains of Bacillus paramycoides) on yield and economics of four perennial aromatic grasses (Vetiveria zizanioides, Cymbopogon citratus, C. martinii, and C. winterianus) in slightly alkaline (pH &gt;8.50) soil. A field experiment was established in a complete randomized block design with two treatments (i.e. with PGPR consortium and without PGPR consortium) and three replications. The changes in growth (height, number of slips, and leaf area index), productivity (fresh shoot‐root biomass and oil yield), quality (important secondary metabolites), and economics (cost of cultivation, gross, and net return) in response to PGPR were observed at three harvests. The species‐specific effects of PGPR were found on the growth and productivity of perennial aromatic grasses. On an average, the highest increase in growth and productivity with the effect of PGPR was found in V. zizanioides followed by other grasses. The highest oil yield 16.38, 71.14, 53.13, and 49.49 kg ha−1 were recorded at third harvest in PGPR consortium treated plots for V. zizanioides, C. citratus, C. martinii, and C. winterianus, respectively. The agronomical economics show the highest net return of 2094.95 $US in the cultivation of V. zizanioides with the application of PGPR.

Consortium of plant growth-promoting rhizobacteria enhances oilseed rape (Brassica napus L.) growth under normal and saline conditions.

A preparation development, which stimulates plant growth under normal and saline conditions, and protects against fungal infections, would increase crop yields and reduce damage in agriculture. This study was conducted using bacterial isolates from rape rhizosphere as a plant growth promoter and an alternative to chemical fertilizers. Three from fifty bacterial isolates: B14 (Pseudomonas sp.), B16 (Sphingobacterium sp.), and B19 (Microbacterium sp.) showed the best in vitro plant growth-promoting (PGP) characteristics. B14 strain had the best antifungal activity against phytopathogens inhibiting growth of B. cinerea, C. acutatum, and P. lingam. Moreover, B14, B16 and B19 isolates coded for several genes involved in PGP activities, aimed at improving nutrient availability, resistance to abiotic stress, and fungal pathogen suppression. Microbial consortium (B14, B16, and B19) had the best effect on rape growth, significantly increasing number of live leaves, compared to the untreated control and single inoculant treatments. Moreover, the consortium induced significant increase in shoots length and chlorophyll content in comparison to Pseudomonas sp. B14 and Microbacterium sp. B19. The consortium also induced plants tolerance to salt stress. The genomic information as well as the observed traits, and beneficial attributes towards rape, make the rhizobacterial consortium an ideal candidate for further development as biofertilizers.

Use of Plant-Growth Promoting Rhizobacteria and Mycorrhizal Fungi Consortium as a Strategy to Improve Chickpea (Cicer arietinum L.) Productivity under Different Irrigation Regimes

Climate change prediction indicates an increased likelihood of precipitation variability and droughts in the Mediterranean region. Previous studies demonstrated that microbial symbionts combined with supplementary irrigation could mitigate climate change effects and boost chickpea production in low-fertility soils. The aim of the study was to assess the effects of inoculation with a consortium of plant growth-promoting rhizobacteria (PGPR) (Pseudomonas sp., Burkholderia sp. and Mesorhizobium sp.) and arbuscular mycorrhizal fungi (AMF) (Rhizophagus irregularis, Funneliformis geosporum and Claroideoglomus claroideum) on growth, grain yield and crude protein content of chickpeas under the following irrigation regimes: I1-no water stress, I2-moderate water stress, I3-strong water-stress, I4-no water stress in critical growth stages of plant cycle development and I5-severe water stress). Plants irrigated only during the critical growth stages of flowering and pod filling showed higher grain yields compared to plants from other water deficit irrigation treatments. Additionally, chickpeas co-inoculated with PGPR and AMF, and irrigated only during critical growth stages, presented higher grain yield than non-inoculated plants without water stress (1.45- and 1.33-fold increase in 2018 and 2019, respectively). Inoculation with beneficial microorganisms and supplemental irrigation at critical stages benefits chickpea growth and should be considered for increasing crop productivity and promoting agricultural sustainability.

Rhizosphere Engineering of Rice with Plant Growth Promoting Rhizobacteria (PGPR) Elicits Crop Growth and Soil Microcosm in Blue-R Dye Contaminated Soil

ABSTRACT This investigation was conducted to determine the ability of plant growth-promoting rhizobacteria (PGPR) to elicit growth of rice plants (var. CO51) in soil incubated with Blue-R textile dye. Two commercial strains of PGPR, nitrogen-fixing Azospirillum lipoferum Az204 and phosphorus-solubilizing Bacillus megaterium var phosphaticum PSB1, were used to prepare a carrier and liquid-based formulations. Seed biotization of carrier-based PGPR consortium followed by a foliar spray substantially resulted in a higher plant biomass, germination percent, and vigor index as compared to non-inoculated plants in Blue-R-amended soil. The photosynthetic efficiency is also higher, which is evident by the total chlorophyll content in PGPR-treated seedlings. Similarly, the carrier-based PGPR inoculated plants revealed higher nutrient uptake as well as N, P, and K content in shoots as compared to the non-inoculated plants. PGPR inoculation through seeds showed better survival and colonization of A. lipoferum Az204 and B. megaterium PSB1 in the rhizosphere. A. liopferum Az204 remarked good colonization in inner tissues of roots, stems, and leaves. It was concluded that PGPR application through seeds enhances crop fitness, modulates rhizosphere services, and alleviates oxidative stress caused by Blue-R in rice plants. Therefore, rhizosphere engineering by PGPR through seeds followed by subsequent foliar sprays can be used as a sustainable strategy for textile wastewater-irrigated soils.

Effects of PGPR Bioinoculants, Hydrogel and Biochar on Growth and Physiology of Soybean under Drought Stress

ABSTRACT The drought ameliorative effects of poly(acrylic acid) hydrogel (HG), biochar (BC) and plant growth-promoting rhizobacteria (PGPR) were evaluated on soybean exposed to drought stress. Prior to sowing, soybean seeds were soaked for 3–4 h in the broth culture of Planomicrobium chinense (MF616408) and Pseudomonas putida (KX574857), while BC (5 g/kg soil) and HG (2 g/kg soil) were mixed with autoclaved soil. Plants were well watered and grown under natural conditions for 35 d, followed by 4 d of drought exposure. While drought stress negatively impacted plant growth, effects of individual application of BC, HG and PGPR in combating the drought stress were noteworthy and a predominant increase in plant biomass by BC and plant antioxidant enzymes (superoxide dismutase (SOD) and catalase (CAT)) and elevated soil nutrients by PGPR were observed. PGPR assisted HG in retaining the soil moisture content (SMC) and further elevated the leaf relative water content (LRWC) and fresh weight (FW) root. The combined application of HG and PGPR consortium was most effective in improving photosynthetic pigments, FW shoot and soil fertility status. Likewise, the combined application of BC and PGPR had stimulatory effects on plant osmoregulants, with BC combined with Pseudomonas putida significantly improving soil nutrient retention. It is inferred that HG and BC in combination with PGPR isolates and PGPR consortium are effective drought mitigating strategies.

Accumulation of beneficial bacteria in the rhizosphere of maize (Zea mays L.) grown in a saline soil in responding to a consortium of plant growth promoting rhizobacteria

PurposeSalt stress reduces plant growth and is now becoming one of the most important factors restricting the agricultural productivity. Inoculation of plant growth-promoting rhizobacteria (PGPR) has been shown to confer plant tolerance against abiotic stress, but the detailed mechanisms of how this occurs remain unclear and the application effects in different reports are unstable. In order to obtain a favorite effect of PGPR inoculation and improve our knowledge about the related mechanism, we performed this study to analyze the mechanism of a PGPR consortium on improving the salt resistance of crops.MethodsA region-specific (Saline land around Bohai Sea in China) PGPR consortium was selected that contains three strains (Pseudomonas sp. P8, Peribacillus sp. P10, and Streptomyces sp. X52) isolated from rhizosphere of Sonchus brachyotus DC. grown in a saline soil. By inoculation tests, their plant growth-promoting (PGP) traits and ability to improve the salt resistance of maize were investigated and shifting in rhizosphere bacterial community of the inoculated plants was analyzed using the high-throughput sequencing technology.ResultsThe three selected strains were salt tolerant, presented several growth promoting properties, and inhibited several phytopathogenic fungi. The inoculation of this consortium promoted the growth of maize plant and enriched the beneficial bacteria in rhizosphere of maize in a saline soil, including the nitrogen fixing bacteria Azotobacter, Sinorhizobium, and Devosia, and the nitrification bacteria Candidatus Nitrososphaera, and Nitrosovibrio.ConclusionsThe bacterial consortium P8/P10/X52 could improve plant growth in a saline soil by both their PGP traits and regulating the rhizosphere bacterial community. The findings provided novel information about how the PGPR helped the plants in the view of microbiome.

A phosphocompost amendment enriched with PGPR consortium enhancing plants growth in deficient soil

ABSTRACT In the present study, we assessed the agronomic value of a formulated plant growth-promoting rhizobacteria (PGPR) consortium combined with a phosphocompost amendment in deficient soil, using three plant models (Phaseolus vulgaris, Zea mays, and Solanum lycopersicum). PGPR consortium contains four strains which have been identified as Pseudomonas sp. DN 13–01, Sphingobacterium suaedae T47, Bacillus pimilus X22, and Bacillus cereus 263AG5, respectively. They have previously displayed their P solubilizing capacity and to have PGPR traits. In this study, the four strains were able also to dissolve potassium (K), with K solubility (KS) indices range between 0.950.03 and 1.210.25 in solid medium and released K values between 30.251.21 and 45.230.84 g-L−1in liquid medium. The bacterial strains also produced acid and alkaline phosphatases, 1-aminocyclopropane-1-carboxylate (ACC) deaminase, protease, cellulase, pectinase, lipase and amylase enzymes. The amendment of deficient soil with phosphocompost enriched with the PGPR consortium increased much more soil productivity and plant growth compared with controls uninoculated. The formulated PGPR consortium combined with phosphocompost gave the best yield in terms of plant height, number of leaves, number of fruits, shoot biomass, root biomass, and dry shoot biomass of the three-plant studied. Simultaneously, the PGPR consortium inoculation increased P and K uptake in the shoots and available P and K in the soil. In summary, our results showed that the application of PGPR consortium combined with phosphocompost amendment increased plant growth in deficient soil.

Enrichment of Organic Manure with Plant Growth Promoting Rhizobacteria Improved the Root and Shoot Growth of Okra (Abelmoschus esculentus L. Moench.)

A well-structured root system is essential to ensure optimal plant growth and yield. Two experiments were conducted to determine the effects of plant growth promoting rhizobacteria (PGPR) on the root system of okra plant. These experiments were arranged with a completely randomized design. The first experiment was conducted in the growth chamber with 8 different bacterial isolates consisting of Methylobacterium sp., Bacillus sp., Bacillus methylotrophicus, Flavobacterium tirrenicum, Providencia stuartii, Azotobacter vinelandii, Methylocystis parvus and PGPR consortium. The second experiment was conducted in the greenhouse and examined the effects of four poultry manure rates, i.e. 0, 6, 12 and 18 ton ha-1, or equivalent to 0, 75, 150 and 225% of recommended rates and how these are altered with the presence or absence of PGPR. The results of the experiments showed that, PGPR significantly improved root architecture; the number and length of lateral roots was increased by 242.86% and 777.79% respectively, as well as the dry weight of the roots and shoots of okra plant by 236.36% and 333.33%, respectively. Moreover applying 150% (12 t.ha-1) of the recommended rate of poultry manure enriched with PGPR was found to be most effective in terms of improving the growth and root attributes of okra plants.

Potential of Salt Tolerant PGPR in Growth and Yield Augmentation of Wheat (Triticum aestivum L.) Under Saline Conditions.

Soil salinity has emerged as a major obstacle to meet world food demands. Halo-tolerant plant growth promoting rhizobacteria (PGPR) are potential bioinoculants to enhance crop productivity in saline agriculture. Current work was aimed at studying individual or synergetic impact of salt tolerant PGPR on wheat growth and yield under saline conditions. A pot experiment was conducted on two wheat genotypes (Aas-11; salt tolerant and Galaxy-13; salt sensitive) inoculated with Pseudomonas fluorescence, Bacillus pumilus, and Exiguobacterium aurantiacum alone and in consortium. The salt tolerant variety (Aas-11) exhibited maximum root fresh (665.2%) and dry biomass (865%), free proline (138.12%) and total soluble proteins (155.9%) contents, CAT (41.7%) activity and shoot potassium uptake (81.08%) upon inoculation with B. pumilus, while improved shoot dry weight (70.39%), water (23.49%) and osmotic (29.65%) potential, POD (60.51%) activity, enhanced root potassium (286.36%) and shoot calcium (400%) were manifested by E. aurantiacum. Highest shoot length (14.38%), fresh weight (72.73%), potassium (29.7%) and calcium (400%) acquisition as well as glycinebetaine (270.31%) content were found in plants treated with PGPR consortium. On the other hand, in the salt sensitive variety (Galaxy-13), P. fluorescens treated plants showed significantly improved leaf-water relations, glycinebetaine (10.78%) content, shoot potassium (23.07%), root calcium (50%) uptake, and yield parameters, respectively. Plant root length (71.72%) and potassium content (113.39%), root and shoot fresh and dry biomass, turgor potential (231.02%) and free proline (317.2%) content were maximum upon PGPR inoculation in consortium. Overall, Aas-11 (salt tolerant variety) showed significantly better performance than Galaxy-13 (salt sensitive variety). This study recommends B. pumilus and E. aurantiacum for the salt tolerant (Aas-11) and P. fluorescens for the salt sensitive (Galaxy-13) varieties, as potential bioinoculants to augment their growth and yield through modulation of morpho-physiological and biochemical attributes under saline conditions.

Aspergillus and Fusarium control in the early stages of Arachis hypogaea (groundnut crop) by plant growth-promoting rhizobacteria (PGPR) consortium

In this study, we have attempted to develop a plant growth promoting rhizobacteria (PGPR) consortia against early-stage diseases in Arachis hypogaea (Groundnut crop) plantation of Andhra Pradesh, India. The dominant PGPRs were selected by considering the various plant growth and protection qualities, followed by characterisation and grouping based on compatibility to form a consortium of PGPRs [Group-1 includes EX-1 (Acinetobacter baumannii stain HAMBI 1846); EX-3 (Pseudomonas aeruginosa strain A1K319); EX-5 (Bacillus subterraneus strain CF1.9); KNL-1 (Bacillus subtilis strain JMP-B); CTR-4 (Enterobacter cloacae strain VITKJ1); ANT-4 (Bacillus subtilis strain SBMP4) and Group-2 includes EX-4 (Pseudomonas otitidis strain SLC8); KDP-4 (Pseudomonas aeruginosa strain Kasamber 11); NLR-4 (Bacillus species ADMK68); ANT-6 (Bacillus subtilis subsp. inaquosorum strain KCTC 13429)]. In addition to resistance to early stage pathogens, in both in vitro and pot experiments the PGPR consortium showed significantly higher germination rate and root induction (Aspergillus niger; A. flavus; Fusarium oxysporum) when compared to control and fertilizer treated groups. In addition, Group 2 was more successful in stimulating and protecting plant growth among the two groups of PGPRs developed. The PGPR consortia developed showed multiple plant growth characteristics, including phosphate solubilization, production of HCN and Indole acetic acid along with broad antagonism against the tested phytopathogens.