Effect Of Plant Growth Promoting Rhizobacteria Research Articles

Isolation， screening and beneficial effects of plant growth-promoting rhizobacteria （PGPR） in the rhizosphere of Leymus chinensis

Isolation， screening and beneficial effects of plant growth-promoting rhizobacteria （PGPR） in the rhizosphere of Leymus chinensis

Protection of Strawberry Plants against Charcoal Rot Disease (Macrophomina phaseolina) Induced by Azospirillum brasilense

Some Plant Growth-Promoting Rhizobacteria (PGPR) can induce protection against pathogens, increasing plant tolerance to various diseases. This so-called biocontrol activity is replacing harmful practices in agriculture caused by the use of agrochemicals. Azospirillum brasilense is one of the PGPR already effectively used as a resistance inducer in several crops. The aim of this study was to evaluate the protective effect of PGPR A. brasilense strains isolated from strawberry and petunia plants (REC3, 2A1, 2A2, and 2E1) against the fungal pathogen Macrophomina phaseolina, which is the causal agent of the strawberry charcoal rot disease. In vitro antagonism assays and enzymatic tests on Petri dishes revealed no direct inhibition on M. phaseolina growth by any of the A. brasilense strains. However, strawberry plants treated with REC3 and 2A1 strains increased callose and lignin deposition and stomatal closure compared to untreated plants. In addition, treatments with either bacterial strains induced a defense response in strawberry plants against virulent isolates of M. phaseolina evidenced by an increased tolerance to the charcoal rot disease. These results suggest that A. brasilense REC3 and 2A1 strains can be used for the activation of innate immunity in strawberry plants as a strategy for managing charcoal rot in a sustainable and environmentally friendly way.

PGPR Mediated Alterations in Root Traits: Way Toward Sustainable Crop Production

The above ground growth of the plant is highly dependent on the belowground root system. Rhizosphere is the zone of continuous interplay between plant roots and soil microbial communities. Plants, through root exudates, attract rhizosphere microorganisms to colonize the root surface and internal tissues. Many of these microorganisms known as plant growth promoting rhizobacteria (PGPR) improve plant growth through several direct and indirect mechanisms including biological nitrogen fixation, nutrient solubilization, and disease-control. Many PGPR, by producing phytohormones, volatile organic compounds, and secondary metabolites play important role in influencing the root architecture and growth, resulting in increased surface area for nutrient exchange and other rhizosphere effects. PGPR also improve resource use efficiency of the root system by improving the root system functioning at physiological levels. PGPR mediated root trait alterations can contribute to agroecosystem through improving crop stand, resource use efficiency, stress tolerance, soil structure etc. Thus, PGPR capable of modulating root traits can play important role in agricultural sustainability and root traits can be used as a primary criterion for the selection of potential PGPR strains. Available PGPR studies emphasize root morphological and physiological traits to assess the effect of PGPR. However, these traits can be influenced by various external factors and may give varying results. Therefore, it is important to understand the pathways and genes involved in plant root traits and the microbial signals/metabolites that can intercept and/or intersect these pathways for modulating root traits. The use of advanced tools and technologies can help to decipher the mechanisms involved in PGPR mediated determinants affecting the root traits. Further identification of PGPR based determinants/signaling molecules capable of regulating root trait genes and pathways can open up new avenues in PGPR research. The present review updates recent knowledge on the PGPR influence on root architecture and root functional traits and its benefits to the agro-ecosystem. Efforts have been made to understand the bacterial signals/determinants that can play regulatory role in the expression of root traits and their prospects in sustainable agriculture. The review will be helpful in providing future directions to the researchers working on PGPR and root system functioning.

A Commentary on Bacterial Inoculation Positively Affects the Quality and Quantity of Flax under Deficit Irrigation Regimes

The present research was conducted to investigate the effect of Plant Growth Promoting Rhizobacteria (PGPR) and deficit irrigation on quality and quantity of flax under field conditions. The effects of PGPRs were evaluated at different irrigation levels. Bacterial strains solubilized phosphate, produced ammonia, indole acetic acid, and siderophore. According to the results bacterial inoculations significantly mitigated the effects of water deficit on oil, linolenic and linoleic acid, protein, sulphur and vitamin contents, shoot and capsules number and harvest index.

Növekedést serkentő rhizobaktériumok használata paradicsom (Solanum lycopersicum L.) növények vízhiányának mérséklésére

Plant growth promoting rhizobacteria (PGPR) can improve the growth, productivity and tolerance of plants under stress conditions. The aim of this study was to investigate the effect of PGPRs on the physiological traits related to photosynthesis, canopy temperature (CT) and yield of tomato hybrids under water scarcity in open field conditions. Seedlings of H-1015 and UG 812J F1 tomato hybrids were treated by B1, B2, B3 bacteria strains before planting, then they were grown under regularly irrigated (RI=ET100%), deficit irrigated (DI=ET50%) and non-irrigated (I0) conditions in the field experiments. During flowering period, a higher chlorophyll fluorescence (Fv/Fm), canopy temperature and lower chlorophyll content (SPAD) were measured for plants treated by B2 and B3 treatments than for untreated plants. From flowering to ripening of tomato fruit, PGPRs influenced negatively the Fv/Fm, positively the SPAD value and canopy temperature, which resulted in a 47.8 to 75.4% increase in the green healthy fruit yield compared to the control. Under severe dry, non-irrigated conditions, B3 treatment increased the green fruits yield by 28.9%, the Brix by 16% and the vitamin C content by 13.6% in comparison with the untreated plants. Under moderate water deficiency using deficit irrigation the plants treated by B3 produced the same marketable yield and 33% lower diseased yield than untreated plants and they produced 9.5% higher Brix and 12.7% higher vitamin C content.

Effects of iron and PGPR on antioxidant status and some physiological traits of triticale under different irrigation levels

A factorial experiment was conducted to study the effects of iron and plant growth promoting rhizobacteria (PGPR) on antioxidant status and some physiological traits of triticale under different irrigation levels. Experimental factors were included irrigation in three levels [(i) normal irrigation (I0) as control; (ii) moderate water limitation (I1) and (iii) severe water limitation (I2)]. Three PGPR levels [(i) no PGPR (P0), (ii) Psedomunas putida (P1), (iii) Azospirillum lipoferum (P2)] and three nano iron oxide levels [(i) without nano iron oxide (F0) as control, (ii) application of 0.3 (F1) and (iii) 0.6 (F2) g/l)]. Results showed that water limitation decreased chlorophyll content, relative water content and grain yield of triticale. Whereas, electrical conductivity, proline content and the activity of catalase (CAT), peroxidase (POD), polyphenol oxidase (PPO) enzymes increased. However, inoculation of plants with PGPR and iron application improved these traits under water limitation condition and normal irrigation. Based on the results, it was concluded that the application of PGPR and iron can be a proper tool for increasing triticale yield under water limitation condition.

Integrated use of bio-organic fertilizers for enhancing soil fertility–plant nutrition, germination status and initial growth of corn (Zea Mays L.)

Abstract The need for cheap and affordable alternate sources of plant nutrient inputs to boost the nutrient level of degraded arable farmlands has been a major concern for soil scientists, agronomists, and local farmers. In 2018, a greenhouse and laboratory pot experiment was carried out under control conditions for 21 weeks to evaluate the effect of plant growth-promoting rhizobacteria (Azospirillium brasilense), spent grain (SG) organic wastes from the beer industry, and chemical fertilizer (CF) on the soil fertility–plant nutrition, corn (Zea Mays L.) germination rate in calcareous soil. The treatments consisted of CK (control), SG (spent grain, 20 g kg−1 soil), Az (Azospirillium seed inoculation), CF (100% of NPK recommended fertilizers), bio-organic (Az with SG), bio-mineral (Az with CF), and organo-mineral (50% of SG +50% of CF). These treatments were arranged in a randomized complete block design and replicated three times. Results showed that after 10 and 21 weeks, SG application significantly increased soil organic carbon by 69% and 67.8%, total nitrogen (TN) by 87.66% and 85.44%, and raised available P (P) by 75.7% and 87.23%, respectively. The final germination percentage (FGP), germination index (GI), coefficient of velocity of germination (CVG) and plant height were significantly higher in the amended pots than that of the control pots after 21 days of planting. The SG with Az treatments had the highest GI, CVG, and FGP of 9.23, 0.19 day−1, and 100 %, respectively, while the least values were obtained in the CF 2.37, 0.12 day−1, and 61.6%, respectively. The highest values of N/P ratio, available Fe2＋, Zn 2 + , and Mn 2 + were 401, 20.35 mg kg−1, 7.27 mg kg−1, and 16.58 mg kg−1 respectively, as well as bio-fertilizers enhanced the dehydrogenase and urease enzymes by 1117.3 μ g TPF ml−1, and 275.4 mg NH 3 − Hg−1h−1 respectively, after 21 weeks of seed sowing. The final results among all treatments were in the order of SG > Bio-organic > Az > Organo-mineral > Bio-mineral > CF > CK. In conclusion, the application of SG and Az is recommended to improve TN and P use efficiencies, micro-nutrients uptake, plant seed germination performance of maize, and enhancement of calcareous soil properties.

Evaluation radiation use efficiency and growth indicators on two mung bean (Vigna radiata L.) genotypes under the influence of biological fertilizers.

Leaf area index (LAI) and radiation use efficiency (RUE) are important ecophysiological characteristics for the realization of crop growth, development, and radiation absorption. A factorial field experiment was carried out base on a randomized complete block design with three replications. Two mung bean genotypes (Dezfouli and Indian) were planted under six fertilization treatments during 2017 and 2018. Six fertilization treatments include: (1) free-living nitrogen fixating bacteria (NFB), (2) phosphorus solubilizing bacteria (PSB), (3) potassium solubilizing bacteria (KSB), (4) free-living nitrogen fixating bacteria + phosphorus solubilizing bacteria + potassium solubilizing bacteria (NFB + PSB + KSB), (5) nitrogen fertilizer (source of urea 46%), and (6) Control (without biological and chemical fertilizers). The maximum LAI was recorded in NFB + PSB + KSB treatment in Dezfouli genotype that compared with controls, increased by 37% and 42%, respectively, in 2017 and 2018. The maximum absorbed radiation at NFB + PSB + KSB treatment increased by 20% and 12% when compared with the control in 2017 and 2018. Also, maximum radiation was proportional to the time of maximum LAI. During 2017 and 2018, the highest RUE (1.21 and 1.03 g MJ–1 m−2, respectively) obtained from Indian genotype in the NFB + PSB + KSB application. The greatest effects of plant growth-promoting rhizobacteria (PGPR) was observed in the NFB + PSB + KSB treatment compared to other treatments. The PGPR could promote mung bean biomass via increasing of LAI and RUE.

68 Effects of Plant Growth-Promoting Rhizobacteria on Fall-Stockpiled Bermudagrass

Abstract Forage production practices have been greatly affected by the increasing cost of N fertilization. Therefore, supplemental and alternative N sources are needed to ensure the economic viability of these systems. A 2-yr, small plot study was designed to evaluate plant growth-promoting rhizobacteria (PGPR) as an alternative form of N fertilizer for fall-stockpiled bermudagrass (Cynodon dactylon). Eighteen 1-m2 ‘Coastal’ bermudagrass plots were treated with a synthetic N fertilizer, DH44 (PGPR strain), DH44+fertilizer, Blend 20 (PGPR blend), Blend 20+fertilizer, and a control, then stockpiled through the fall. Two PGPR applications were applied in late-August and again 30 d later. Fertilizer and PGPR+fertilizer plots received (NH4)2SO4, at a rate of 56 kg N/ha. One-third of each plot was clipped to 2.5 cm in November, December, and January, respectively. Forage DM yield, CP, NDF, ADF, and ADL were determined via wet chemistry at the Auburn University Ruminant Nutrition Laboratory (Auburn, AL). Data were analyzed using PROC MIXED (SAS 9.4, SAS Inst., Cary, NC) as a completely randomized design. Yield was greatest (P ≤ 0.0318) for Blend 20+fertilizer, but it was not different (P = 0.2552) from that of the synthetic fertilizer (1,914 kg ha-1, 1,768 kg ha-1, respectively). Concentration of CP was least (P ≤ 0.0437) for DH44 and Blend 20 treatments (90 g kg-1 and 92 g kg-1, respectively). Concentrations of NDF for the control were different (P ≤ 0.0045) for all treatments except synthetic fertilizer (P = 0.1092). Concentrations of ADF were not different (P ≥ 0.1613) excluding the control (P ≤ 0.0525; 342.8 g kg-1and 358.0 g kg-1, respectively). In vitro true digestibility (IVTD) was not different (P = 0.0947) among all treatments (463.1 g kg-1). All yield and nutritive value parameters were greater (P ≤ 0.0246) in Year 2. These results indicate that PGPR is a viable option for biofertilization of fall-stockpiled bermudagrass; however, further investigation into the effects of PGPR inoculants at a field scale are needed.

Impact of Inoculation with Pseudomonas aestus CMAA 1215T on the Non-target Resident Bacterial Community in a Saline Rhizosphere Soil.

Plant growth reduction caused by osmotic stress, pathogens, and nutrient scarcity can be overcome by inoculation with plant growth-promoting rhizobacteria (PGPR). Knowing the effects of PGPR on the microbial community beyond those on plant growth can bring new options of soil microbiota management. The present study aimed to investigate the effect of inoculation with the newly described Pseudomonas aestus CMAA 1215T [a 1-aminocyclopropane-1-carboxylate (ACC) deaminase and glycine-betaine producer] on the rhizosphere bacterial community of Zea mays in natural (non-salinized) and saline soil. The bacterial community structure was assessed by sequencing the V6-V7 16S ribosomal RNA using the Ion Personal Genome Machine™. The non-metric multidimensional scaling (NMDS) of the OTU profile (ANOSIM P < 0.01) distinguishes all the treatments (with and without inoculation under saline and natural soils). Inoculated samples shared 1234 OTUs with non-inoculated soil. The most abundant classes in all samples were Alphaproteobacteria, Gammaproteobacteria, Actinobacteria, Acidobacteriia, Bacteroidia, Thermoleophilia, Verrucomicrobiae, Ktenodobacteria, and Bacilli. The inoculation, on the other hand, caused an increase in the abundance of the genera Bacillus, Bryobacter, Bradyrhizobium, "Candidatus Xiphinematobacter", and "Candidatus Udaeobacter" independent of soil salinization. "Candidatus Udaeobacter" has the largest Mean Decrease in Gini Values with higher abundance on inoculated salted soil. In addition, Pseudomonas inoculation reduced the abundance of Gammaproteobacteria and Phycisphaerae. Understanding how inoculation modifies the bacterial community is essential to manage the rhizospheric microbiome to create a multi-inoculant approach and to understand its effects on ecological function.

Effects of different doses of Plant-Growth-Promoting Rhizobacteria (PGPR) granules on wheat yield

Plant growth promoting rhizobacteria (PGPR) are the soil bacteria inhabiting around/on the root surface and are directly or indirectly involved in promoting plant growth and development. This study was conducted at research field of Agriculture Research Station, Belachapi, Dhanusa, Nepal in 2018 to identify the effects of PGPR on wheat production. The experiment was laid out in Randomized Complete Block Design with three replications. Eight treatments namely, T1: Control; T2: Recommended doses of fertilizers (RDF) (100:50:50 N:P2O5:K2O kg/ha); T3:10 t/ha Farm Yard Manure (FYM); T4: PGPR 12.5 kg/ha ; T5: PGPR 25 kg/ha; T6: PGPR 7 kg/ha; T7: PGPR 12.5 kg/ha + ½ RDF; T8: PGPR 7 kg/ha + ½ FYM, were applied in this experiment. Wheat variety NL-971 was used. The results showed that the thousand grain weight showed significant result. The treatment with 10 t/ha FYM was found the best for spike length (8.267cm), grains per five spikes (160) and Thousand grain weight (49.28 g). Whereas, the highest yield (2.064 t/ha) was obtained with application of PGPR 7 kg/ha + ½ FYM. The PH content was found the highest (5.453) with application of RDF. The maximum organic matter content (1.763) and N content (0.1179%) were found with application of PGPR 12.5 kg/ha. Similarly, the highest phosphorus content (75.83 mg/kg) was found with application of PGPR7 kg/ha while the highest potassium content (72.51 mg/kg) was obtained with application of PGPR 25kg/ha. Overall, there was positive impact of application of PGPR on wheat production.

PENGARUH PGPR AKAR BAMBU APUS DAN PUPUK LIMBAH CAIR NANAS TERHADAP PERTUMBUHAN BAWANG DAUN UNTUK INFORMASI MASYARAKAT

Increasing agricultural crop production, especially onion, can be done by improving the optimal growing environment for plants. Plant roots can be optimized for the absorption of nutrients and water in the process of photosynthesis. One way that can be used is by applying Plant Growth Promoting Rhizobacteria (PGPR). In addition to increasing the content of micro and macro elements in the soil can also support the growth of leek plants obtained by applying Pineapple Liquid Waste (LCN) made using bacterial isolation and can meet the needs of nutrients in plants. This study aims to determine the effect Plant Growth Promoting Rhizobacteria (PGPR) from Apus (Gigantochola apus) bamboo root and Pineapple Liquid Waste (LCN) fertilizer on the growth of leeks (Allium fistulosum L.), then the results of this study are treated as community information in the form of Leaflets. The method used in this study was an experiment using a Completely Randomized Design (CRD) system consisting of 4x4 factorials with 3 replications. Based on the results of calculations and data analysis, the results show that there is an effect of PGPR and LCN on the growth of scallions on the height and number of tillers per scallion plant family, but there is no influence on pseudo stem circumference and wet weight per scallion plant family, and the results of this study can be used as a source of public information in the form of leaflets with an average percentage included in good eligibility criteria.

High impact of PGPR on biostatistic of Aphis craccivora (Hemiptera: Aphididae) on yardlong bean

Abstract. Triwidodo H, Listihani. 2020. High impact of PGPR on biostatistic of Aphis craccivora (Hemiptera: Aphididae) on yardlong bean. Biodiversitas 21: 4016-4021. Plant growth-promoting rhizobacteria (PGPR) are root colonizing bacteria that live and develop near plant roots, which boost plant growth and act as antagonist agents. This research is aimed to asses the effect of PGPR on biostatistics of Aphis craccivora Koch on yardlong bean (Vigna unguiculata subsp. sesquipedalis). The research was conducted at WiSH Laboratory in Bogor, Indonesia, by tested PGPR mixture of Rhizobium, Bacillus polymyxa, and Pseudomonas fluorescens. The research discovered that the application with seed treatment and watered of PGPR affects the biology of Aphis craccivora in terms of lengthening its stadia of second instar nymph, lengthening its life cycle, and declining its fecundity. The application of PGPR also affects the biostatistics of Aphis craccivora. PGPR applied plants have a gross reproduction rate (GRR), net reproduction rate (Ro) and intrinsic increase rate (r) of Aphis craccivora that are lower than control. PGPR could slower the doubled time (DT) of Aphis craccivora to become lengthier than control. PGPR could improve plant growth: it could increase the number and length of roots, number of root nodules, plant height, number of leaves, as well as length and density of trichome.

Isolation and Characterization of Indigenous Plant Growth-Promoting Rhizobacteria (PGPR) from Cardamom Rhizosphere.

The present study was conducted to explore the native plant growth-promoting (PGP) bacteria from cardamom rhizosphere in few districts of Kerala and Tamilnadu under cardamom cultivation. The isolates obtained were screened for their PGP characteristics and their beneficial effect on cardamom was evaluated. Of the total 88 isolates, ten were screened as promising based on their performance in growth promoting attributes such as production of indole acetic acid, gibberellic acid, siderophore, hydrogen cyanide, heavy metal tolerance and antibiotic resistance. Diazotrophy of the screened isolates were tested by nitrogenase assay and evaluated using the diversity of nif genes. Genetic analysis was carried out to assess the phylogenetic relationship using 16S rRNA sequencing. The phylogenetic analysis exhibited clear clustering of isolates into three phyla namely Firmicutes, Actinobacteria and γ-proteobacteria. Majority of the isolates were grouped into Bacillus and Pseudomonas at genus level. Three different plant inoculation study at nursery and field level, viz., Bacillus subtilis TAUC1, Bacillus subtilis TAUC2 and Pseudomonas putida TAUC10. The combined inoculation of bioinoculants were superior over individual inoculation with respect to growth, soil and plant nutrient content, biochemical constituents, rhizosphere population, soil enzyme activities and yield. Hence the present study reveals the potential effect of PGPR for bioinoculant production for enhancing growth and development of cardamom under field conditions.

Interactions Between Microorganisms and a Seaweed-Derived Biostimulant on the Growth and Biochemical Composition of Amaranthus hybridus L.

Natural biostimulants such as plant growth-promoting rhizobacteria (PGPRs) and seaweed extracts are used in agriculture to improve crop yield in an environmentally friendly approach. However, interaction effects between different biostimulants are seldom investigated. This study aimed to determine the combined effect of PGPRs and Kelpak® (KEL), a seaweed-derived extract, on the growth and biochemical composition of Amaranthus hybridus, a traditional leafy vegetable of South Africa. A pot trial was conducted with 6 treatments—control (distilled water), Bacillus licheniformis (BL) inoculum, Pseudomonas fluorescens (PF) inoculum, 1% KEL, and combination treatments of KEL + BL and KEL + PF. These were applied 3 times to A. hybridus seedlings at 2 weekly intervals prior to harvesting after 6 weeks. Growth parameters and biochemical content were quantified in the harvested material. Kelpak® significantly improved growth (leaf number and area, shoot and root length, and fresh weight) and chlorophyll and carotenoid content. Treatments with 2 microorganisms had a significant negative effect on growth and pigment content. However, the combination treatments significantly improved growth and photosynthetic pigment content to similar levels as the KEL treatment. The mineral content was significantly increased for most minerals when treated with PF and decreased when treated with KEL and KEL + BL. Treatment with 2 bacterial strains and KEL caused a significant decrease in superoxidase dismutase activity with an additive effect when applied in combination. This suggests stress reduction in A. hybridus. Combined use of PGPR and seaweed extracts promises to be an eco-friendly strategy to improve the production and mineral content of traditional leafy vegetables such as A. hybridus.

Inoculation of maize seeds with Pseudomonas putida leads to enhanced seedling growth in combination with modified regulation of miRNAs and antioxidant enzymes

Bacteria that positively interact with plant roots are defined as plant growth promoting rhizobacteria (PGPR). Although the positive effect of PGPR on plant growth has been widely studied, their impact on genetic regulation during plant growth processes remains largely unknown. Therefore, this study aimed to gain a deeper understanding of the regulatory role of miRNA and redox enzymes in response to PGPR at the maize seedling stage in leaf growth zone which consists of the meristem, elongation and mature zones. For this purpose, growth of the third leaf was monitored in response to Pseudomonas putida (P. putida) KT2440 at phenotypic, physiological, cellular, kinematic, and transcriptional levels. This application resulted in an increase of 15% in shoot length, 56% in both shoot fresh/dry weight, 10% in chlorophyll amount, 8% in mature cell length, 15% in leaf elongation rate, and 7% in cell production; meanwhile final leaf length was unchanged, while leaf area and leaf width decreased by 22% and 16%, respectively. Ascorbate peroxidase and glutathione reductase activity increased throughout the leaf growth zone indicating a possible role in PGPR-plant interaction during transition between cell division, expansion and differentiation processes. The expression analysis of cell cycle check point marker genes revealed that CycA2_1 was mainly responsible for promoting cell proliferation in meristem. miR160, miR169 and miR408 were differentially expressed in the meristem, indicating their indirect regulatory roles in the cell division response to PGPR. In addition, miR160, miR319 and miR396 were downregulated in the elongation zone, which draws attention to their possible role in regulating cell elongation processes. In summary, cell cycle, redox and miRNA regulation in maize seedling growth zones in response to P. putida were investigated for the first time in this study.

Special issue in honour of Prof. Reto J. Strasser - Can be performance indexes used to select plant growth-promoting rhizobacteria?

The plant growth-promoting rhizobacteria (PGPR) are bacteria that colonize the rhizosphere or roots, resulting in a beneficial effect on plants. The evaluation of the PGPR effects is mostly based on growth biometric measurements, but there is little information about using the chlorophyll (Chl) fluorescence. We used rhizobacteria to treat canola seeds and evaluate their effects on leaf area, dry mass, and Chl fluorescence. In order to select PGPR, we suggest the JIP-test as a method to evaluate their effects using the performance indexes. The biometric measurements and JIP-test parameters allowed to group bacterial isolates into different groups. We observed that some PGPR increased the energy absorption efficiency/or flux. We conclude that the performance indexes can be used to differentiate the interaction of plants and PGPR and to select rhizobacteria with a potential for plant growth promotion.

Growth and Yield Response of Upland Rice to Application of Plant Growth-Promoting Rhizobacteria

This study evaluated the effects of plant growth-promoting rhizobacteria (PGPR) isolates in enhancing upland rice growth and yield. Bacteria were isolated, screened for growth-promoting activities in vitro, biochemically identified, and tested under screenhouse conditions at the Philippine Rice Research Institute (PhilRice). Isolates exhibited growth-promoting activities, such as indole-3-acetic acid (IAA) production, tricalcium phosphate solubilization, 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase activity, siderophore production, and starch hydrolysis. The screenhouse experiment was conducted with upland rice (PSB Rc23) as the test crop, sterilized and natural soils, and recommended rate of inorganic fertilizers (RRIF) as other source variables. Results showed that significantly heavier shoot and root fresh weights are evident in plants grown in sterilized soil. Plants treated with full RRIF exhibited superior growth in terms of plant height, shoot and root weights, and grain yield. Among inoculated and fertilized plants, comparable growth promotion was obtained with Acidovorax delafieldii combined with half inorganic fertilizer rate, in terms of root fresh weight, shoot and root dry weights, plant height, grain yield, and nitrogen, phosphorus, and potassium (NPK) uptake. Overall findings show that PGPR (A. delafieldii) in combination with 50% RRIF is as effective as full RRIF in enhancing growth and yield of PSB Rc23 rice, implying that dependence on chemical fertilizer can be reduced utilizing this PGPR. However, further evaluation of these bacterial isolates in actual field conditions is necessary to uncover their efficiency as potential biofertilizer.

Impacts of plant growth promoters and plant growth regulators on rainfed agriculture.

Demand for agricultural crop continues to escalate in response to increasing population and damage of prime cropland for cultivation. Research interest is diverted to utilize soils with marginal plant production. Moisture stress has negative impact on crop growth and productivity. The plant growth promoting rhizobacteria (PGPR) and plant growth regulators (PGR) are vital for plant developmental process under moisture stress. The current study was carried out to investigate the effect of PGPR and PGRs (Salicylic acid and Putrescine) on the physiological activities of chickpea grown in sandy soil. The bacterial isolates were characterized based on biochemical characters including Gram-staining, P-solubilisation, antibacterial and antifungal activities and catalases and oxidases activities and were also screened for the production of indole-3-acetic acid (IAA), hydrogen cyanide (HCN) and ammonia (NH3). The bacterial strains were identified as Bacillus subtilis, Bacillus thuringiensis and Bacillus megaterium based on the results of 16S-rRNA gene sequencing. Chickpea seeds of two varieties (Punjab Noor-2009 and 93127) differing in sensitivity to drought were soaked for 3 h before sowing in fresh grown cultures of isolates. Both the PGRs were applied (150 mg/L), as foliar spray on 20 days old seedlings of chickpea. Moisture stress significantly reduced the physiological parameters but the inoculation of PGPR and PGR treatment effectively ameliorated the adverse effects of moisture stress. The result showed that chickpea plants treated with PGPR and PGR significantly enhanced the chlorophyll, protein and sugar contents. Shoot and root fresh (81%) and dry weights (77%) were also enhanced significantly in the treated plants. Leaf proline content, lipid peroxidation and antioxidant enzymes (CAT, APOX, POD and SOD) were increased in reaction to drought stress but decreased due to PGPR. The plant height (61%), grain weight (41%), number of nodules (78%) and pod (88%), plant yield (76%), pod weight (53%) and total biomass (54%) were higher in PGPR and PGR treated chickpea plants grown in sandy soil. It is concluded from the present study that the integrative use of PGPR and PGRs is a promising method and eco-friendly strategy for increasing drought tolerance in crop plants.

Isolation, characterization and screening of PGPR capable of providing relief in salinity stress

Environmental stresses such as drought, temperature, salinity, air pollution, heavy metals, pesticides, and soil pH are major limiting factors in crop production because they affect almost all plant functions. Soil salinization is a serious stress condition causing major problem for crop productivity. To combat this salinity stress, Plant growth promoting rhizobacteria (PGPR) is considered as innovative, effective and ecofriendly approach. Plant growth promoting rhizobacteria (PGPR) have various direct and indirect mechanisms which can be correlated with their ability to form biofilms, chemotaxis, and the production of exopolysaccharide, indole-3-acetic acids (IAA) and aminocyclopropane-1- carboxylate (ACC) deaminase Investigations on the interaction of PGPR with other microbes and their effect on the physiological response of crop plants under different soil salinity regimes are still at an incipient stage. An experiment was conducted to investigate the effect of PGPR on lowering down the salt stress. Treatments were control (T 1 ), Salt tolerant isolate KH-1 (T 2 ), Salt tolerant isolate KH-2 (T 3 ), Salt tolerant isolate KH-3 (T 4 ), PGPR-I (Pseudimonas) (T 5 ), PGPR-II (Azotobacter) (T 6 ). Rice was sown under saline conditions at Soil Salinity Research Institute, Pindi Bhattian. With the inoculation of salt tolerant PGPR, plant growth and yield was improved. Result showed significant increase in plant height, biomass and yield over control. Inoculation of salt tolerant isolate KH-2 produced maximum grain yield in rice (4267 kg/ha) followed by PGPR-II and it was statistically significant from all other treatments along with control. It is concluded that with the application of salt tolerant isolate (KH-2), there is significant increase in rice production.