Application Of Plant Growth Promoting Rhizobacteria Research Articles

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

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

Plant Growth-Promoting Rhizobacteria: 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.

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

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

Restoration of fumigated soil biota with plant growth-promoting rhizobacteria to counteract Meloidogyne incognita (Tylenchida: Heteroderidae) boosts eggplant growth and defenses

AbstractThis study investigated the effectiveness of two plant growth-promoting rhizobacteria (PGPR) formulations, Bio Arc® 6% WP (BA, Bacillus megaterium) and BECTO Grow Roots® (BGR; Serratia marcescens, Pseudomonas putida, and P. fluorescens). Additionally, it focused on naturally infested soil that had undergone metam potassium fumigation to reduce root-knot nematode (RKN), specifically Meloidogyne incognita. It aimed to monitor eggplant response to soil biodiversity changes for 60 days of the experiment under greenhouse conditions. Our data showed that soil fumigation eliminated nematodes and reduced other microorganisms significantly. In sterilized soil, plant fresh root weight significantly decreased after the elimination of soil biota. Moreover, BGR achieved the highest plant growth vigor [fresh root (18.48%), fresh shoot (23.52%), and fresh plant weight (21.03%)], followed by BA [fresh root (11.98%), fresh shoot (20.77%), and fresh plant weight (16.38%), respectively]. Plant growth traits increased significantly following the second reinoculation of PGPR after a month. Also, the same data trend was observed in treatments inoculated with RKN + PGPR. Furthermore, BGR treatments exhibited consistent efficacy in controlling nematode infection, maintaining superior vegetative growth compared to BA treatments over time. However, BA treatments displayed a decline in plant growth when faced with repeated nematode infection. The range of gall, egg mass, and second-stage juvenile (J2s) numbers diminished after inoculation-infected plants with RKN and PGPR compared with infected plants alone. Biochemical changes in eggplant roots cultivated in sterilized soil exposed significant enhancement in total sugars, protein, and nonenzymatic antioxidants (flavonoids and phenolic content), with antioxidant activity enhanced upon inoculation of PGPR and RKN. Oppositely, the levels of enzymatic antioxidants (catalase, peroxidase, and superoxide dismutase) decreased significantly with single and double PGPR application. However, the decline was less pronounced in the BGR treatments than in BA. In contradiction of oxidative enzymes, reinoculated PGPR + RKN multiplied significantly in reinfested RKN treatments. Our findings support the use of PGPR combinations, in particular, for preventive inoculation against M. incognita. They also enhance plant growth-promoting factors and stimulate plant defenses against inevitable soil reinfestation following soil fumigation.

Real-Time PCR (qtPCR) to Discover the Fate of Plant Growth-Promoting Rhizobacteria (PGPR) in Agricultural Soils.

To optimize the application of plant growth-promoting rhizobacteria (PGPR) in field trials, tracking methods are needed to assess their shelf life and to determine the elements affecting their effectiveness and their interactions with plants and native soil microbiota. This work developed a real-time PCR (qtPCR) method which traces and quantifies bacteria when added as microbial consortia, including five PGPR species: Burkholderia ambifaria, Bacillus amyloliquefaciens, Azotobacter chroococcum, Pseudomonas fluorescens, and Rahnella aquatilis. Through a literature search and in silico sequence analyses, a set of primer pairs which selectively tag three bacterial species (B. ambifaria, B. amyloliquefaciens and R. aquatilis) was retrieved. The primers were used to trace these microbial species in a field trial in which the consortium was tested as a biostimulant on two wheat varieties, in combination with biochar and the mycorrhizal fungus Rhizophagus intraradices. The qtPCR assay demonstrated that the targeted bacteria had colonized and grown into the soil, reaching a maximum of growth between 15 and 20 days after inoculum. The results also showed biochar had a positive effect on PGPR growth. In conclusion, qtPCR was once more an effective method to trace the fate of supplied bacterial species in the consortium when used as a cargo system for their delivery.

Combined control of plant diseases by Bacillus subtilis SL44 and Enterobacter hormaechei Wu15

Co-incubation of plant growth promoting rhizobacteria (PGPRs) have been proposed as a potential alternative to pesticides for controlling fungal pathogens in crops, but their synergism mechanisms are not yet fully understood. In this study, combined use of Bacillus subtilis SL44 and Enterobacter hormaechei Wu15 could decrease the density of Colletotrichum gloeosporioides and Rhizoctonia solani and enhance the growth of beneficial bacteria on the mycelial surface, thereby mitigating disease severity. Meanwhile, PGPR application led to a reorganization of the rhizosphere microbial community through modulating its metabolites, such as extracellular polymeric substances and chitinase. These metabolites demonstrated positive effects on attracting and enhancing conventional periphery bacteria, inhibiting fungal pathogens and promoting soil health effectively. The improvement in the microbial community structure altered the trophic mode of soil fungal communities, effectively decreasing the proportion of saprotrophic soil and reducing fungal plant diseases. Certain combinations of PGPR have the potential to serve as precise instruments for managing plant pathogens.

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

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

The Coupling Effects of PGPR Inoculation and Foliar Spraying of Strigolactone in Mitigating the Negative Effect of Salt Stress in Wheat Plants: Insights from Phytochemical, Growth, and Yield Attributes

Salt stress has detrimental effects on wheat plants at several physiological, biochemical, and molecular levels. This stress leads to suppressed growth, reduced grain yield, and poor quality of harvested grains. However, two approaches have shown promise for improving wheat salt tolerance: using a synthetic strigolactone analog called GR24 and applying plant growth-promoting rhizobacteria (PGPR). GR24 plays a vital role in regulating plant growth and development and in defense against various stresses. Conversely, PGPR are beneficial bacteria that colonize the rhizosphere of plants and promote their growth through multiple mechanisms. In our study, we investigated the effects of salinity on the growth and yield traits of two different wheat cultivars and explored the combined role of PGPR and GR24 in mitigating the impact of salt stress. We created three different salinity levels using NaCl in pots (original, 5 dS m−1, and 10 dS m−1) and inoculated wheat seeds with a salt-tolerant Bacillus velezensis UTB96 strain. In addition, we applied 10 μM GR24 via foliar application during the pollination stage. Our observations showed that salt stress negatively affected wheat’s growth, yield, and phytochemical properties compared to the control. However, both single and combined applications of PGPR and GR24 mitigated the adverse effects of salinity. The combined treatment had a more substantial impact than either alone in inducing and improving biochemical and ionic characteristics. These included decreasing Na+ content in both leaves and roots, and EL, H2O2, and MDA content in leaves while increasing K+ content in both leaves and roots, growth and yield-related traits, RWC, chlorophyll pigments, total protein, soluble sugar, starch, proline, GB, and antioxidant enzyme activity (APX, POX, and CAT) of leaves. In conclusion, integrating PGPR and GR24 can efficiently induce salt tolerance and improve plant growth under stressed conditions. This combined approach has the potential for broad applicability in supporting plant growth in the presence of salt stress.

NanoBiofertilizer and its Application in Sustainable Agriculture, Crop Specific Nutrients Delivery and Environmental Sustainability: A Review

Probiotic bacteria are increasingly in demand in the food and feed industries. A growing population and finite resources require efficient ways to maximize yields. Probiotic bacteria are gaining popularity in the food and feed industries due to their unique combination of benefits and values, which include consumer health interests, sustainability values, food innovation, and potential business opportunities. The use of conventional fertilizers can increase crop production but can also cause runoff and toxicity issues. A nanobiofertilizer offers improved crop nutrition and reduces application rates. Slow-release properties minimize environmental losses while nanoscale particle size enhances nutrient absorption. If nanobiofertilizers are closely regulated, they can boost yields without destroying the soil and aquatic ecosystems. In recent years, nanobiofertilizers have received considerable attention. Plant extracts and microbes are used in green synthesis to produce eco-friendly nanoparticles. Crop-specific nutrient release can be tailored using modified nanoparticle surfaces. Controlled nutrient delivery is achieved by smart nanocarrier systems that adapt to changing soil moisture, pH, and microbial activity. Combined applications of plant growth-promoting rhizobacteria have been reported that they can enhance crop growth in synergy. This review presents an overview of the most recent studies on nanobiofertilizers, as well as the issues connected with their environmental implications, safety, and regulation, presenting a roadmap for the responsible use of nanobiofertilizers, which aims to enhance food security while protecting the environment for future generations.

Plant growth-promoting rhizobacteria (PGPR) improve the growth and quality of several crops

Plant growth-promoting rhizobacteria (PGPR) are known to have the effect of promoting plant growth. In this paper, three PGPR strains were selected from the previous work, which had plant growth-promoting activities such as phosphate solubilization, nitrogen fixation, phosphorus mobilization, etc. These strains named FJS-3(Burkholderia pyromania), FJS-7(Pseudomonas rhodesiae), and FJS-16(Pseudomonas baetica), respectively, were prepared into solid biological agents. Three widely planted commercial crops (tea plant, tobacco, and chili pepper) were selected for PGPR growth promotion verification. The results showed that the new shoots of tea seedlings under PGPR treatment were much more than the control. We also used tobacco, another important crop in Guizhou, to test the growth-promoting effect of individual bacteria, and the results showed that each of them could promote the growth of tobacco plants, and FJS-3(Burkholderia pyrrocinia) had the best effect. In addition, we carried out experiments on tobacco and pepper using multi-strain PGPR, the tobacco plants' height, fresh, and root weight increased by 30.15 %, 37.36 %, and 54.5 %, respectively, and the pepper plants' increased by 30.10 %, 56.38 % and 43.18 %, respectively, which both showed significantly better effects than that of a single strain. To further test the field performance, field trials were carried out in a mature Longjing43 tea plantation in Guizhou. There were four treatments: no fertilization (T1), combined application of PGPR biological agent and compound fertilizer (T2), only application of PGPR (T3), and only application of compound fertilizer (T4). In terms of yield, grouped with or without PGPR, there was a 15.38 % (T2:T4) and 92.31 % (T3:T1) increase between them, respectively. The tea's yield and tea flavor substances such as tea polyphenols, caffeine, and theanine were detected, and the T2 showed the most significant positive effect on both sides. Especially, an important indicator of Matcha green tea is the color, chlorophyll content was then tested, and PGPR application increased it and improved the appearance. All these results demonstrated that the PGPR we screened could significantly promote plant growth and quality improvement, and had good application potential in crop planting, which could contribute to environmental protection and economic growth.

Alleviation of heat stress by ACC Deaminase and Exopolysaccharide Producing Plant-Growth-Promoting Rhizobacteria in Solanum melongena L.

Background: The current study was carried out to assess the alternative role of high temperature tolerant plant growth promoting rhizobacteria (PGPR) in alleviation of heat stress adverse effect in eggplant.Methods: PGPR was assessed for PGP potentialities and investigated for1‐aminocyclopropane‐1‐carboxylate (ACC deaminase), and exopolysaccharide under normal and high temperature environment. The impact of PGPR application on plant physiology and biochemistry was investigated under normal and high temperature environments and plant growth regulators were evaluated using High Performance Liquid Chromatography (HPLC).Results: A significant impediment for morphological and physiological parameters of eggplant cultivars was observed during heat stress in absence of PGPR inoculation. The results showed that ACC‐deaminase produced by PGPR boosted up significantly the extracellular polymeric substances (EPS) accumulation, conversion of ACC into α‐ketobutyrate and ammonia, and reduce consequently the impact of high temperature on eggplant development.Conclusion: PGPR inoculation showed an alternative strategy to improve eggplant growth and development under high temperature condition in order to preserve agriculture sustainability and healthy crops.Keywords: ACC‐deaminase; Extracellular polymeric substances; Heat stress; PGPR; Solanum melongena

Plant-Growth-Promoting Rhizobacteria and Arbuscular Mycorrhizal Fungi May Improve Soil Fertility and the Growth, Nutrient Uptake, and Physiological Performance of Batavia Lettuce (Lactuca sativa L. var. longifolia) Plants

A greenhouse experiment was realized to investigate the effects of plant-growth-promoting rhizobacteria (PGPR) and arbuscular mycorrhizal fungi (AMF) on soil quality and the growth, nutrient uptake, and physiological performance of Batavia lettuce (Lactuca sativa L. var. longifolia). For this purpose, six fertilization treatments were applied: (i) inorganic fertilization (I.F.—control, i.e., usual/conventional fertilization), (ii) I.F. + PGPR, (iii) I.F. + PGPR + AMF, (iv) manure (MAN), (v) MAN + PGPR, and (vi) MAN + PGPR + AMF. Soil fertility was influenced by the treatments, and soil respiration (CO2 flux) was significantly increased after applications of PGPR and AMF. Following MAN fertilization in particular, an approximately sixfold higher soil respiration value was recorded following the MAN + PGPR + AMF treatment compared to the control (I.F.). Root, leaf, and total biomass dry weights were significantly affected by the PGPR and AMF applications, mainly following the I.F. treatment. In contrast, K, Mg, and Fe uptake was significantly influenced by PGPR and AMF application following the MAN treatment. The SPAD value, performance index (PI), photosynthetic rate, and stomatal conductance were significantly higher in the I.F. + PGPR + AMF-treated plants compared to the control plants. Overall, these data prove the beneficial roles of PGPR and AMF in soil quality and fertility and the nutrient uptake and physiological performance of lettuce plants. However, further clarification is needed in the near future to test the interaction effects between PGPR, AMF, and the type of fertilizer used (organic or inorganic).

Potential of Drought Tolerant Rhizobacteria Amended with Biochar on Growth Promotion in Wheat.

Drought stress is the prime obstacle for worldwide agricultural production and necessitates innovative strategies for enhancing crop resilience. This study explores the efficacy of plant growth-promoting rhizobacteria (PGPR) and biochar (BC) as sustainable amendments for mitigating the effects of drought on wheat growth. Multiple experiments were carried out on isolated strains to assess their drought tolerance potential and multiple plant growth-promoting attributes. Experiments in the laboratory and natural environment were conducted to assess the impact of plant growth-promoting rhizobacteria, biochar, and their synergistic application on various growth parameters of wheat. The results revealed that the drought-tolerant PGPR strains (Bacillus subtilis and Bacillus tequilensis), alongside biochar (rice husk), alleviated the phytotoxic impact of drought by increasing the root length from 17.0% to 70.0% and shoot length from 30.0% to 82.0% as compared to un-inoculated stressed controls. The total chlorophyll and carotenoid contents of the plants were substantially increased to 477% and 423%, respectively, when biochar and PGPR were applied synergistically. Significant enhancements in membrane stability index, relative water content, proline, and sugar level were achieved by combining biochar and bacterial strains, resulting in increases of 19.5%, 37.9%, 219%, and 300%, respectively. The yield of wheat in terms of plant height, spike length, number of spikelets per spike, and number of grains per spike was enhanced from 26.7% to 44.6%, 23.5% to 62.7%, 91.5% to 154%, and 137% to 182%, respectively. It was concluded that the biochar-based application of PGPR induced drought tolerance in wheat under water deficit conditions, ultimately improving the production and yield of wheat.

Enhancing Drought Resistance and Yield of Wheat through Inoculation with Streptomyces pactum Act12 in Drought Field Environments

Drought stress is the primary abiotic factor affecting wheat growth, development, and yield formation. The application of plant growth-promoting rhizobacteria (PGPR) represents an environmentally sustainable approach to mitigate the impacts of drought stress on wheat. This study conducted field experiments using two winter wheat varieties, the drought-sensitive variety Jimai 22 and the drought-resistant variety Chang 6878, aiming to investigate the effects of Streptomyces pactum Act12 inoculation on photosynthetic characteristics, physiological parameters, and yield traits during the jointing, heading, and middle-filling stages under drought stress. The results revealed that drought stresses significantly reduced chlorophyll content, leaf area, biomass, and yield in wheat, while Act12 inoculation significantly increased chlorophyll content, photosynthetic efficiency, antioxidant enzyme activity such as superoxide dismutase (SOD) and peroxidase (POD), osmolyte content (proline and soluble proteins), and decreased malondialdehyde (MDA) content. These combined effects alleviated drought stress, resulting in increased biomass and yield in wheat. Under drought stress, an increase in leaf proline content of 13.53% to 53.23% (Jimai 22) and 17.17% to 43.08% (Chang 6878) was observed upon Act12 inoculation. Moreover, a decrease in MDA content was recorded of 15.86% to 53.61% (Jimai 22) and 13.47% to 26.21% (Chang 6878). Notably, there was a corresponding increase in yield of 11.78% (Jimai 22) and 13.55% (Chang 6878). In addition, grain quality analysis revealed a significant improvement in grain hardness with Act12 inoculation. Therefore, Act12 demonstrates the potential for enhancing the sustainable development of wheat production in arid and semi-arid regions.

Exploiting the role of plant growth promoting rhizobacteria in reducing heavy metal toxicity of pepper (Capsicum annuum L.).

Microorganisms are cost-effective and eco-friendly alternative methods for removing heavy metals (HM) from contaminated agricultural soils. Therefore, this study aims to identify and characterize HM-tolerant (HMT) plant growth-promoting rhizobacteria (PGPR) isolated from industry-contaminated soils to determine their impact as bioremediators on HM-stressed pepper plants. Four isolates [Pseudomonas azotoformans (Pa), Serratia rubidaea (Sr), Paenibacillus pabuli (Pp) and Bacillus velezensis (Bv)] were identified based on their remarkable levels of HM tolerance in vitro. Field studies were conducted to evaluate the growth promotion and tolerance to HM toxicity of pepper plants grown in HM-polluted soils. Plants exposed to HM stress showed improved growth, physio-biochemistry, and antioxidant defense system components when treated with any of the individual isolates, in contrast to the control group that did not receive PGPR. The combined treatment of the tested HMT PGPR was, however, relatively superior to other treatments. Compared to no or single PGPR treatment, the consortia (Pa+Sr+Pp+Bv) increased the photosynthetic pigment contents, relative water content, and membrane stability index but lowered the electrolyte leakage and contents of malondialdehyde and hydrogen peroxide by suppressing the (non) enzymatic antioxidants in plant tissues. In pepper, Cd, Cu, Pb, and Ni contents decreased by 88.0-88.5, 63.8-66.5, 66.2-67.0, and 90.2-90.9% in leaves, and 87.2-88.1, 69.4-70.0%, 80.0-81.3, and 92.3%% in fruits, respectively. Thus, these PGPR are highly effective at immobilizing HM and reducing translocation in planta. These findings indicate that the application of HMT PGPR could be a promising "bioremediation" strategy to enhance growth and productivity of crops cultivated in soils contaminated with HM for sustainable agricultural practices.

Effect of Plant Growth Promoting Rhizobacteria (PGPR) on Growth and Yield of Soybean

This study aimed to (1) examine the effect of giving PGPR (Plant Growth Promoting Rhizobacteria) to increase soybean growth and production and (2) obtain the best dose of PGPR to increase soybean growth and production. The research was carried out in Tontalete Village, Kema District, North Minahasa Regency, North Sulawesi from June 2021 to October 2021. The field experiment was arranged in a Randomized Block Design (RBD). The treatment tested was the concentration of PGPR, which consisted of P0 = 0 ml/l (control), P1 = 5 ml/l, P2 = 10 ml/l, P3 = 15 ml/l, and P4 = 20 ml/l. The treatment was repeated three times, so there were 15 experimental units. Parameters observed were: plant height, number of branches, number of pods per plant, percentage of damaged pods per plant, the weight of 100 dry seeds, and seed yield/plot. The data were analyzed using the Analysis of Variance (ANOVA) and continued with the mean difference test using the Least Significant Difference Test (LSD) at the 5% level. The results showed that the application of PGPR affected the growth and yield of soybeans by increasing plant height, the number of pods per plant, and dry seed yield. The highest dry seed yield was achieved at PGPR concentrations of 10 ml/l and 15 ml/l, which were 1.34 g and 127.87 g, equivalent to 1.34 tons ha-1 and 1.28 tons ha-1, respectively.

Evaluation of Soil Total Nitrogen as an Indicator of Soil Bacterial Community Response to Biochar and Plant Growth-Promoting Rhizobacteria Applications

Biochar and plant growth-promoting rhizobacteria (PGPR) are widely used as an amendment for soil physicochemical properties and soil bacterial community diversity. In Guangxi, China, we carried out a study to determine how PGPR and biochar influence the soil’s environmental stability in an Eucalypt plantation. We applied biochar and PGPR in a contrasting application manner to an acidic red loam soil. Thus, three treatments were set up as 5 × 1010 CFU·mL−1 PGPR-only (MB0), 20 t·hm−2 biochar-only (B20), and co-application of 20 t·hm−2 biochar and 5 × 1010 CFU·mL−1 PGPR (MB20), as well as no biochar and no PGPR (M0B0). Our results indicated that MB20 significantly decreased the soil total nitrogen (TN) and increased the soil total phosphorus (Soil TP), soil ammonium nitrogen (NH4+), and soil water content (SWC) when compared with the control. The MB20 also significantly increased the Simpson, ACE, and Chao indices of the soil bacterial community’s diversity relative to the control. We also observed a significant effect of the Soil TN on both the bacterial community and the functional diversity in soil. These findings may indicate that assessing the soil N status is expected to be an essential indicator of the soil microenvironment’s response to biochar and PGPR applications.

Bacillus cereus: an effective bio-inoculant for promoting salt stress tolerance of rice seedlings under saline soil conditions

Plant growth-promoting rhizobacteria (PGPR) are a powerful tool to maintain sustainable agriculture and promote plant resistance to biotic and abiotic types of stress. Salinity, a major abiotic stress hampers plant growth, development, and yield. Salt-tolerant PGPR are effective agents for ameliorating salinity effects on rice plants. The present study endeavored to isolate, determine halotolerant ability, characterize Plant Growth Promoting (PGP) traits, and finally observe the effect of PGPR strain on plant growth promotion of rice plants under saline and non-saline conditions. Based on the 16S rRNA gene sequencing technique, the rhizobacterial strain DB2 was identified as Bacillus cereus ATCC 14579(T) from NCMR, NCCS Pune. To check the growth-promoting ability, the strain was inoculated with two rice genotypes named Chinsurah Nona I (salt tolerant-non aromatic) and Badshabhog (aromatic) under polyhouse conditions. Results showed a significant increment in relative water content (RWC), total chlorophyll content (TCC), root length (RL), and shoot length (SL) in both rice genotypes inoculated with DB2 under both saline and non-saline conditions. Under non-saline conditions enhancement of RWC, TCC, RL, and SL was better in DB2 inoculated Chinsurah Nona I than in Badshabhog inoculated with DB2. Whereas, DB2-inoculated Badshabhog showed more recovery of RWC, TCC, RL, and SL than DB2-inoculated Chinsurah Nona I under saline conditions. Under salt stress conditions, inoculation with the rhizobacterial strain showed a significant reduction in electrolytic leakage (EL) in rhizobacteria inoculated with both rice genotypes. Moreover, DB2 inoculation showed a significant reduction in Na+ content in the roots of Chinsurah Nona I (44.6%) and Badshabhog (24.5%) rice genotypes. The present study has indicated that the application of salt-tolerant PGPR may be an effective and sustainable solution for rice cultivation under salt-stress conditions.

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.

Enhancing seed and cob characteristics in reciprocal crosses between purple waxy corn and sweet corn through plant growth-promoting rhizobacteria application

Maize is one of the major cereal crops. Different high yielding as well as hybrid varieties have been growing for higher maize production. Various fertilizers have also been used to increase the maize yield. But yield target is not achievable always and the fertilizers had detrimental effects on soil properties also. For sustainable maize production, we conducted a combined study of reciprocal cross and application of plant growth-promoting rhizobacteria (PGPR). In this study, we examine the traits of seeds and cobs resulting from reciprocal crossings between Purple Waxy Corn (PWC) and Sweet Corn (SC) that were subjected to treatment with PGPR. The outcomes of reciprocal crossings on the traits of seeds and cobs exhibited a distinctiveness that diverged from that of their respective progenitors. The seeds and cobs from reciprocal crosses exhibited novel variation in their characteristics. If the male parent is PWC, the F1 seeds exhibit alterations in both color and type on a single cob, so modifying the traits of the seeds in a direction aligns with those of the female parent. If the male parent is SC (♂), then F1 exhibits a phenotypic alteration in seed color, nugget color and seed type on a single cob which represents a distinctive trait variation between the two parents. An interaction between the application of PGPR, both in terms of timing and concentration and the kind of corn, was seen to affect the seed width, seed thickness and sugar content. The results of present study will be helpful for sustainable maize production.