EVALUATION OF PGPR ISOLATES AS BIOSTIMULANTS FOR ENHANCING GROWTH IN COMMON BEAN (Phaseolus vulgaris L.)

This study was conducted to isolate plant growth promoting rhizobacteria (PGPR) from wheat rhizosphere and to evaluate their potential use for improving growth, yield and nutrient uptake of wheat. Eight PGPR strains were isolated and studied for their morphological and cultural characteristics, phosphate solubilization and indole acetic acid (IAA) production. All isolates produced IAA ranging from 5.5–31.0 μg/ml, while four isolates were P-solubilizers. On the basis of morphological characteristics, IAA production and P solubilization, strains WPR-32, WPR-42, and WPR-51 were identified as PGPR and selected for further study. Efficiency of these three PGPR isolates and their mixtures (combinations) at two N levels (N at the rate of 50 and 100 kg ha−1) was evaluated in wheat under greenhouse conditions. Application of PGPR significantly increased plant height, shoot fresh weight and shoot dry weight by 25, 45, and 86%, respectively, while increase in root length, root fresh and dry weight was 27, 102, and 76%, respectively, over the un-inoculated control. PGPR also increased number of tillers per plant, 1000-grain weight and grain yield by 23, 48 and 59% over the control. Uptake of N and P by plant shoot was increased by three-fold, while K uptake was increased by 58% with PGPR application. The rate of increase in growth, yield and nutrient accumulation was even higher in treatments receiving combined application of PGPR and N-fertilizer. The concentration of [sbnd]N and available P in soil also increased with PGPR treatments. Results indicated that among the PGPR isolates, efficiency of mixture of isolates was higher than the individual isolates and isolate S7 was relatively more consistent than the remaining strains. This study demonstrated that application of PGPR with N fertilizer increased the fertilizer N efficiency by increasing N content and N uptake in plants. This study also indicated that use of PGPR had similar effects on growth, yield and nutrient uptake of wheat when compared with the low N level, i.e. N50. Therefore, application of PGPR with low fertilizer rates could be a viable supplementary strategy for maximum benefits in terms of cost of production and sustaining productivity. However, the applicability of this approach has to be tested in further field studies.

To guarantee a sufficient phosphorus supply for plants, a rapid and permanent mobilization of phosphorus from the labile phosphorus fractions is necessary, because phosphorus concentrations in soil solution are generally low. Several plant growth-promoting rhizobacteria (PGPR) have shown potential to enhance phosphorus solublization and nodulation of legumes when co-inoculated with Rhizobium . This investigation was undertaken to assess the feasibility and compatibility of two mineral phosphorus fertilizers; diammonium phosphate (DAP), triple super phosphate (TSP), poultry manure (PM) and two PGPR strains on the growth, nodulation, yield, nutrient uptake and protein content of common bean ( Phaseolus vulgaris ) under deficient phosphorus supply. Integrated application of mineral phosphorus (P), PM and PGPR significantly increased shoot height, shoot fresh weight, shoot dry weight and leaf chlorophyll content by 67, 160, 51 and 106%, respectively, while increase in root length, root fresh weight and root dry weight was 79, 161, and 187%, respectively, over unfertilized control without PGPR application. Integrated use of different P sources and PGPR also increased number of nodules per plant, nodule fresh weight and nodule dry weight by 158, 107 and 168% over the control. Treatment with PGPR significantly increased number of pods per plant and grain yield by 224 and 96%, respectively over the control. Co-inoculation with Bradyrhizobium sp. strain MN-S and Agrobacterium sp. strain Ca-18 demonstrated two-fold increase in the proportion of nitrogen (N) and P uptake as well as protein content of the common bean grain was increases by 48%. Therefore, application of PGPR with low P fertilizer rates and PM could be a viable supplementary strategy for maximum benefits in terms of cost of production and sustaining productivity. Key words: Phaseolus vulgaris L., plant growth promoting rhizobacteria (PGPR), nodulation, yield, phosphorus deficiency, protein.

This study evaluated the effects of Plant Growth-Promoting Rhizobacteria (PGPR) types and concentrations on the growth and yield of soybean (Glycine max L. Merrill). The experiment was conducted from December 2023 to February 2024 in Krapyak Village, Jepara Regency, Indonesia, at an altitude of approximately 20 m above sea level on latosol soil. The study employed a factorial Completely Randomized Block Design (CRBD) with two factors: PGPR type (without PGPR, bamboo root PGPR, and commercial PGPR) and PGPR concentration (0, 10, 20, and 30 ml L⁻¹), with three replications. Observed parameters included vegetative growth traits (plant height, number of branches, flowering time), yield components (total pods per plant, empty pods, 100-seed dry weight, seed dry weight per plot), and biomass accumulation (plant fresh and dry weight). The results showed that PGPR type significantly affected the number of branches at 4 weeks after planting (WAP), total pod number, and plant fresh and dry weight. Commercial PGPR produced the highest number of branches, total pods, and biomass accumulation. PGPR concentration of 20 ml L⁻¹ resulted in the highest number of branches at 4 WAP. Significant interactions between PGPR type and concentration were observed for plant fresh and dry weight. However, PGPR application had no significant effect on plant height, flowering time, 100-seed dry weight, or seed dry weight per plot. Overall, the results indicate that PGPR effectiveness depends on microbial source and optimal concentration, with commercial PGPR showing greater potential to enhance soybean vegetative growth and pod formation under field conditions.

Growth promotion and yield enhancement of peanut ( Arachis hypogaea L.) by application of plant growth-promoting rhizobacteria

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.

The objective of this study was to evaluate the growth response of oil palm seedlings to the application of Sugarcane Filter Cake (blotong) and PGPR at the pre-nursery stage. The research was conducted at the Research and Educational Garden ( Experimental farm) in Maguwohardjo Village, Depok Sub-district, Sleman Regency, Special Region of Yogyakarta. This study took place from December 2024 to March 2025. The research method used was a factorial experiment arranged in a Completely Randomized Design (CRD) with two factors. The first factor was the dosage of Sugarcane Filter Cake, with four treatment levels: control (NPK 3 gram), 100 g, 150 g, and 200 g per seedling. The second factor was the application of PGPR, with four concentration levels: control (0 ml), 5 ml, 10 ml, and 15 ml per polybag. The data were analysed using Analysis of Variance (ANOVA), and the results were further tested using Duncan’s Multiple Range Test (DMRT) at a 5% significance level. The observed parameters included plant height, number of leaves, stem diameter, shoot fresh weight, shoot dry weight, root fresh weight, root dry weight, root volume, and leaf area. The results showed no interaction between the Sugarcane Filter Cake dosage and PGPR concentration in influencing the growth of oil palm seedlings. The application of a 100 g dose of Sugarcane Filter Cake per seedling showed optimal growth for the parameters of plant height and number of leaves.The application of sugarcane filter cake can replace in the NPK fertilizer. The application of PGPR up to a concentration of 15 ml did not have a significant effect on any of the observed parameters for the oil palm seedlings in the pre-nursery.

Limited availability of nutrients to crops is a major agricultural concern. Deteriorated soil health and poor fertility status decrease the bioavailability of essential nutrients to the plants. Consequently, organic soil amendment biochar is gaining attention due to its potential benefits. Rhizobacterial inoculation, are also documented as an effective technology for mobilization of immobile nutrients in soil. However, limited literature is available on combined use of rhizobacteria and biochar. Therefore, this study was carried out to examine the changes in the nutrient content of einkorn wheat and the change in some soil properties during the application of plant growth-promoting rhizobacteria (PGPR) with biochar. Four doses of biochar (0, 2.5, 5, and 10%) were applied with and without PGPR in the study. Biochar increased the growth criteria such as plant fresh weight (PFW), plant dry weight (PDW), root fresh weight (RFW), root dry weight (RDW), number of tillers, germination rate (GR) and potassium (K), calcium (Ca), sodium (Na), iron (Fe), copper (Cu), zinc (Zn), manganese (Mn), and nickel (Ni) elements. While PGPR application increased soil pH, dry and fresh weight of root, R/S, K, Ca, Mg, Fe, and Ni contents, and it caused a decrease in PH, PFW, tillers, GR, P, Cu, and Zn values. Combined biochar applications and PGPR had a significant effect on the pH, RFW, R/S, P, Na, and Cu. In conclusion, the combination of biochar and PGPR applications has shown a positive effect in terms of soil properties, plant growth, and element contents of einkorn wheat.

Tannery wastewater is a major environmental pollutant that introduces toxic compounds, including chromium (Cr), into agricultural soils, posing significant challenges to plant growth and productivity. This research uniquely evaluates the efficacy of three specific plant growth-promoting rhizobacteria (PGPR)— Paenibacillus polymyxa , Bacillus amyloliquefaciens , and Pseudomonas putida —for mitigating Cr stress in rice ( Oryza sativa L.). In this study, O. sativa plants were exposed to different levels of tannery wastewater (0%, 50%, and 100%) in a controlled pot experiment to assess the impact of P. polymyxa , B. amyloliquefaciens and P. putida on various morpho-physio-biochemical traits. Results from the present study revealed that the Cr toxicity induced a substantial decrease in shoot length, root length, number of leaves, leaf area, shoot fresh weight, root fresh weight, shoot dry weight, root dry weight, chlorophyll-a, chlorophyll-b, total chlorophyll, carotenoid content, net photosynthesis, stomatal conductance, transpiration rate, soluble sugar, reducing sugar, non-reducing sugar contents, calcium (Ca 2+ ), magnesium (Mg 2+ ), iron (Fe 2+ ), and phosphorus (P) contents in the plants. However, Cr stress also induced oxidative stress in the plants by increasing malondialdehyde (MDA) and hydrogen peroxide (H 2 O 2 ), which also led to an increase in various enzymatic and nonenzymatic antioxidants and also the gene expression and sugar content. Furthermore, a significant ( P < 0.05) increase in proline metabolism, the AsA–GSH cycle, and the pigmentation of cellular components was observed. Addition of P. polymyxa , B. amyloliquefaciens and P. putide into the soil significantly alleviated Cr toxicity effects on O. sativa by improving photosynthetic capacity and ultimately plant growth. Increased activities of antioxidant enzymes in organic acid and PGPRs-treated plants seem to play a role in capturing stress-induced reactive oxygen species as was evident from lower levels of MDA and H 2 O 2 . Moreover, the application of different PGPRs enhanced both the abundance and diversity of the rhizosphere microbiome, with bacterial population levels and Shannon diversity indices significantly increasing. A marked reduction in daily Cr intake and associated health risks was also observed under these treatments, and proteomic responses under Cr stress. Research findings, therefore, suggested that the application of PGPRs can ameliorate Cr toxicity in O. sativa seedlings and resulted in improved plant growth and composition under metal stress.

Pre-nursery is one of the important stages in preparing oil palm planting materials. PGPR (Plant Growth Promoting Rhizobacteria) are beneficial bacteria for plants that colonize around plant roots. Leri water is one of the by-products of household activities that contain beneficial properties for plants. This study aims to determine the application of PGPR and air leri on the growth of oil palm seedlings in pre-nursery and to determine the interaction between the application of PGPR and air leri on the growth of oil palm seedlings in the pre-nursery. This research was conducted from February to July to October 2022 in Maguwoharjo Village, Sleman, Yogyakarta. The study used an experimental method which was arranged in a completely randomized design (CRD) consisting of two factors. The first factor is the PGPR application, which consists of four levels, namely 0 ml, 10 ml, 20 ml, and 30 ml. The second factor is the application of leri water consisting of three levels, namely every 2 days, 4 days, and 6 days. Observations were analyzed using variance at the 5% level of significance. If there is a significant difference then proceed with Duncan's multiple range test at the 5% level of significance. The results showed that there was an interaction between the application of PGPR and leri water on seedling height, stem diameter, number of leaves, root length, root volume, and shoot fresh weight, crown dry weight, root dry weight, plant fresh weight, and plant dry weight. Whereas in the application of PGPR and leri water to root fresh weight there was no interaction and each treatment was not significantly different.

Establishment of plant communities through revegetation offers good scope for rehabilitation of degraded ecosystems like post mined land. Seeding the plants with Plant Growth Promoting Rhizobacteria (PGPR) during revegetation process can augment the growth of the plants besides enriching the soil with macro and micronutrients. The present study investigates the ability of PGPR isolates Brevibacillus borstelensis (KY 614550) and Bacillus subtilis (KY 614549) isolated from the mine soil of Neyveli Lignite Corporation India Limited to promote plant growth on mine soil. Seed germination test indicated that the PGPR isolates had a stimulatory effect on Vigna radiata seedlings as evident by significant increase in per cent germination, root length, shoot length and fresh weight over control. PGPR application alone and in combination with organic amendments (Press mud and Farm yard manure at 25% and 50% levels) during pot culture trials resulted in growth promotion of Casuarina junghuhniana saplings (C.N- Australian pine; Family- Casuarinaceae) with apparent increase in shoot length, chlorophyll content, carbohydrate and protein levels. Antioxidant enzyme levels were found to be higher in control plants indicating the efficiency of treatment combinations in combating the biotic and abiotic stress when plants were grown on mine soil. This apparent effect resulting from the seeding of the tree crop with potent PGPR isolates can be translated to develop a healthy soil ecosystem in degraded mined lands.

Aims:The aim of this study was to isolate, characterize, and evaluate the plant growth-promoting traits and effects on rice seed germination of PGPR strains obtained from rice rhizosphere soil samples.Methodology and results: Three bacteria (PGPR-A, PGPR-B and PGPR-C) were isolated from Oryza sativa rhizosphere soil samples from different fields of Nalgonda district, Telangana, India, using a nutrient medium.Serial dilution of different rice rhizosphere soil samples was done to isolate the PGPR bacteria, and then subculturing of morphologically different isolates was done to purify the isolates.Out of eight pure isolates, three bacteria showed variable PGPR characteristics such as hydrogen cyanide (HCN) production, ammonia production, nitrogen fixation, IAA production and phosphate solubilization.Morphological, biochemical characterization and extracellular enzyme production were also performed on all three PGPR isolates, which gave varied results.Among these three isolates, PGPR-B is highly positive for HCN production.It showed positive results for ammonia production, nitrogen fixation and phosphate solubilization activity.IAA production was negative with all three PGPR bacteria.Out of three PGPR isolates, rice seeds incubated with the PGPR-B isolate showed enhanced seed growth.Hence, molecular identification was carried out to identify this bacterium.After DNA isolation and PCR reaction, the PCR product was used to determine its 16S rDNA sequence, which was submitted to NCBI, and its accession number was PP817225.It was 99.86% closely related to Bacillus tropicus strain MCCC 1A01406.Conclusion, significance and impact of study: Among three PGPR isolates (A, B and C), PGPR-B isolate showed more PGPR characteristics.Separate incubation of rice seeds with three PGPR isolates proved that PGPR-B as a potential isolate to increase rice seed growth than other two PGPR isolates (A and C).

Mitigating negative impacts of drought on oak seedlings performances through plant growth-promoting rhizobacteria.

Alfalfa (Medicago sativa L.) is an outstanding species used for the remediation of heavy metal-contaminated soil, and our previous research has shown that PGPR can promote plant growth under high-concentration lead stress. This discovery has forced scientists to search for PGPR strains compatible with alfalfa to develop an innovative bioremediation strategy for the remediation of lead-contaminated soil. This study used lead-tolerant rhizosphere soil of red clover as experimental material; cultured, isolated, and screened 52 excellent lead-tolerant bacteria that promote rhizosphere growth; and then inoculated them into alfalfa. Marked differences existed in the secretion of auxin, protease, and ACC deaminase among these strains. The results indicated that Pseudomonas spp. (strain Y2), Pseudomonas spp. (strain Y22), and Bacillus spp. (strain Y23) exhibited a strong growth-promoting ability in alfalfa, and there was no antagonistic reaction among the three strains, enabling their coexistence. The pot experiment manifested that strains Y2, Y22, Y23, and YH (a mixture of Y2, Y22, and Y23) could increase the plant height, root length, fresh and dry weight above ground, and fresh and dry weight below ground of alfalfa. They could all significantly raise the chlorophyll content and antioxidant enzyme activity in alfalfa (p < 0.05) and the content of malondialdehyde (MDA) in alfalfa. Furthermore, the concurrent inoculation of three distinct types of plant growth-promoting rhizobacteria (PGPR) significantly diminished lead (Pb) concentrations in rhizosphere soil, enhanced the levels of available potassium (AK) and available phosphorus (AP), and augmented the capacity of plants to absorb Pb. The results imply that PGPR can be employed to facilitate plant growth and microbial-assisted remediation of lead and other heavy metal-contaminated soil and establish a basis for further research on the growth-promoting mechanism of PGPR in plants.

Salah satu permasalahan dalam usaha budidaya tanaman secara intensif di Indonesia adalah cekaman kekeringan yang menyebabkan ketersediaan air tanah menjadi rendah sehingga tidak mencukupi kebutuhan tanaman. Salah satu upaya mengatasi kondisi cekaman kekeringan yaitu dengan pemberian Plant Growth Promoting Rhizobacteria. Artikel ini bertujuan untuk mengetahui pengaruh interaksi antara pemberian Plant Growth Promoting Rhizobacteria dan cekaman kekeringan terhadap perkecambahan dan pertumbuhan vegetatif kacang kedelai. Artikel dilaksanakan pada bulan Februari sampai bulan Maret tahun 2024. Rancangan penelitian yang digunakan adalah RAK pola faktorial diulang sebanyak tiga kali dengan faktor pertama yaitu konsentrasi Plant Growth Promoting Rhizobacteri diantaranya: 0%, 1%, 1,5%, 2% dan 2,5% dan faktor kedua pada kadar air tanah 100 % kapasitas lapang dan 50 % kapasitas lapang. Hasil artikel menunjukan bahwa pada fase perkecambahan terdapat interaksi antara konsentrasi Plant Growth Promoting Rhizobacteria dengan cekaman kekeringan terhadap kecepatan tumbuh dan panjang hipokotil, sedangkan pada fase pertumbuhan vegetatif terdapat interaksi terhadap tinggi tanaman pada umur 21 dan 30 hari setelah tanam. Secara mandiri konsentrasi Plant Growth Promoting Rhizobacteria berpengaruh terhadap daya kecambah, bobot kering kecambah, dan panjang epikotil. Pada fase perkecambahan konsentrasi yang berpengaruh baik yaitu 1,5 % dan 2 %. Pada fase pertumbuhan vegetatif konsentrasi Plant Growth Promoting Rhizobacteria yang berpengaruh baik terhadap jumlah daun, volume akar, bobot kering akar, bobot kering pupus, ratio pupus akar dan bobot kering tanaman konsntrasi 2 % dan 2,5 %. One of the problems in intensive plant cultivation in Indonesia is drought stress which causes groundwater availability to become low so that it is not sufficient for plant needs. One of the efforts to overcome drought stress conditions is by giving Plant Growth Promoting Rhizobacteria. This research aims to determine the effect of the interaction between giving Plant Growth Promoting Rhizobacteria and drought stress on the germination and vegetative growth of soybeans. The research was carried out from February to March 2024. The research design used was RAK factorial pattern repeated three times with the first factor being the concentration of Plant Growth Promoting Rhizobacteri including: 0%, 1%, 1.5%, 2% and 2.5% and the second factor is soil moisture content at 100% field capacity and 50% field capacity. The research results showed that in the germination phase there was an interaction between the concentration of Plant Growth Promoting Rhizobacteria and drought stress on growth speed and hypocotyl length, while in the vegetative growth phase there was an interaction on plant height at 21 and 30 days after planting. Independently, the concentration of Plant Growth Promoting Rhizobacteria influences germination capacity, dry weight of sprouts, and epicotyl length. In the germination phase, the concentrations that have a good effect are 1.5% and 2%. In the vegetative growth phase, the concentration of Plant Growth Promoting Rhizobacteria had a good effect on the number of leaves, root volume, root dry weight, shoot dry weight, root shoot ratio and plant dry weight, concentrations of 2% and 2.5%.

The aims of this research is to find out the influence of the application of sago waste compost and PGPR on the increase in groundnut growth and yield and to obtain the dose of sago waste compost and PGPR concentration that able to increase the growth and yield of groundnut had been conducted in January to March 2016 in Maba Sangaji Village, Kota Maba Subdistrict, East Halmahera Regency. The research used factorial randomized complete block design consisting of two factors with three replication. Factor I was the dose of sago waste compost consisted of four levels: K0 = without sago waste compost (control), K1 = sago waste compost of 10 t ha-1, K2 = sago waste compost of 15 t ha-1, and K3 = sago waste compost of 20 t ha-1. Factor II was concentration of Plant Growth Promoting Rhizobacteria (PGPR) consisted of 4 levels: P0 = without PGPR (control), P1 = PGPR of 5 ml l-1, P2 = PGPR of 10 ml l-1, and P3 = PGPR of 15 ml l-1. The observation consisted of growth components of plant height, the number of leaves, leaf area, crop dry weight, and crop growth rate, and yield components of the number of pods, filled pods, empty pods, pod weight, grain weight, and weight of 100 grain. Research result shows that there was no interaction between the treatment of sago waste compost and PGPR. However, separately, treatments of sago waste compost and PGPR had the significant influence on the growth and yield of groundnut. The highest groundnut yield was obtained in the treatment of sago waste compost with the dose of 20 t ha-1. Grain weight obtained was 17.51 g or an increase of 52.15% compared to those of treatment without application of sago waste compost and yield of grain weight per hectare was 2.80 t ha-1. The inoculation of PGPR increased the growth and yield of groundnut. The application of PGPR with the concentration of 10 and 15 ml-1 produced better crop growth. The higher result was obtained in the treatment of PGPR with the concentration of 10 and 15 ml l-1with grain weight of 15.46 g and 16.81 g plant-1 or an increase of 31.15% and 42.6%, respectively, compared to control,whereas, grain weight per hectare was 2.47 t ha-1 and 2.69 t ha-1, respectively.