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Fenugreek (Trigonella foenum-graecum L.) is a valuable medicinal plant, which is widely distributed throughout the world. It has been known that plant growth promoting rhizobacteria (PGPR) have positive effects on the quality and quantity of medicinal plants under different soil water levels. For this reason, a factorial experiment was conducted on the basis of a randomized complete block design (RCBD) to evaluate PGPR effects on the morphophysiological and phytochemical traits of fenugreek under different soil water levels. This study was conducted in two separate experiments: after the six-leaf stage and after the flowering stage. In the experiments, the treatments were plant growth promoting rhizobacteria (PGPR) including the control, Sinorhizobium meliloti, Pseudomonas fluorescens, a combination of S. meliloti and P. fluorescens, and different soil water levels (i.e. 100, 80, 60 and 40% of field capacity (FC) in three replications. The results showed that the highest seed weight per plant was obtained by inoculation with the S. meliloti and P. fluorescens combination at 100% FC after the two developmental stages. The maximum concentrations of nicotinic acid and trigonelline were observed for the combination of S. meliloti and P. fluorescens at the soil water content of 40% FC after the six-leaf stage and for S. meliloti at the soil water content of 40% FC after the flowering stage. The correlation and stepwise regression analyses showed positive effects of PGPR application on the morphophysiological and phytochemical traits of fenugreek plants under different soil water levels.

PGPB play an important role in agricultural systems, and contain broad range of bacterial genera. Therefore, in this study, seeds of wheat were inoculated with 18 rhizobacteria strains belonging to Azotobacter chroococcum (14SPI, 44SP-2, 16SP-2, 14SP2-1), Pseudomonas sp. (24A-1, 34A-2, 34SPIII, 35SP-2), Agrobacterium sp. (14A-4, 22SP-1), Rhizobium sp. (12A-3), Sphingomonas sp. (37SP), Stenotrophomonas sp. (16SP7-2), Citrobacter sp. (44 A-4S), Achromobacter sp. (14SPIII), Klebsiella oxytoca (4A-1), Beijerinckia sp. (2SP-5) and 36 A-2L isolate, to determine the effects on growth and yield of spring wheat under greenhouse condition. In this study, 18 carrier-based PGPB treatments along with one negative (B0: no inoculation) and two positive controls (B0N50 and B0N100; containing 50% and 100% of urea fertilizer, respectively) were used. The results showed that inoculation treatments had no significant effect on some plant parameters (e.g., chlorophyll index, spike length) compared with the B0, but revealed significant differences (p <.01) in other parameters such as seed weight, seed number, total dry weight, and N uptake of grain. B0N100, B0N50, and 14A-4 significantly enhanced the total dry weight (shoot, root, spike, and leave) by 35%, 32.4%, and 28.5% as compared to the control, respectively. These trends were observed in seed number and seed weight, too. Highest content of grain N uptake and Zn uptake were in 14SPI, content of P was in 44SP-2, and K and Fe content were achieved in 16SP-2 and 14SPI. In general, Agrobacterium sp. 14A-4, A. chroococcum (14SP-I, 16SP-2, and 44SP-2) were effective isolates to improve qualitative and quantitative traits of wheat. [ABSTRACT FROM AUTHOR]

It is important to investigate and develop the strategies and methodologies to maintain the sustainability of plant production. A two-year field study was performed to evaluate calendula response to individual form and also mixtures of selected bio organic fertilizers. The effects of co-inoculation of two plant growth promoting rhizobacteria (PGPR), humic acid (HA), vermicompost (VC), and combinations of these bio organics were investigated in two calendula cultivars, Isfahan multi petalled (MP) and single petalled (SP). The experimental design was a factorial randomized complete block with three replicates. Based on the combined analysis of two years, mean flower yield was highest for the MP cultivar treated by VC + PGPR. Flower essential oil was higher in the MP cultivar than the SP cultivar and did not vary with fertilizers. The highest harvest index of flowers obtained from the MP cultivar treated by HA + PGPR. Furthermore, nutrient contents of leaves increased by fertilizers and combined application of bio organics gave the highest values of nitrogen, phosphorus and potassium contents in calendula leaves. The present results indicate that the selected bio organic fertilizers can be used to obtain higher levels of quality and yield in sustainable agricultural practices. [ABSTRACT FROM AUTHOR]

Given the negative environmental impacts of chemical fertilizers, application of phosphate solubilizing bacteria (PSB) as an ecofriendly and safe approach are becoming increasingly popular as substitute to chemical P fertilizers. Nowadays phosphatic microbial fertilizers (PMF) which are formulated by integration of rock phosphate (RP), organic residues, and efficient microorganisms including PSB are being used as biofertilizers to meet plant phosphorus demand. Accordingly, in this study, first P solubilization efficiency of PSBs (including Pseudomonas fluorescens Tabriz, Pseudomonas putida Tabriz, Pseudomonas sp. C16-2O, Enterobacter sp. S16-3, Bacillus megaterium JK6, Bacillus firmus SN1, and Pantoeaagglomerans P5) was checked under in vitro conditions, then the effectiveness of formulated PMFs was evaluated in pot culture using an autoclaved soil. PMFs of seven PSBs were prepared by adding PSB to the substrate consisting of RP, sulfur powder, and bagasse. The results of in vitro investigation on phosphate solubility of PSBs in qualitative (HD/CD) and quantitative procedures in Sperber medium indicated that there were significant differences among the bacteria and different sources of phosphorus. Moreover, P solubility index (HD/CD) showed a good correlation (r = 0.75, p < 0.05) with P solubility in liquid medium. The highest phosphate solubilization was measured by P. agglomerans P5>Pseudomonas sp. C16-2O >Enterobacter sp. S16-3 > P. putida Tabriz > B. megaterium JK6 > P. fluorescens Tabriz > B. firmus SN1, respectively, and dissolution of phosphorus from tricalcium phosphate (TCP) was higher than from RP. The results obtained from the greenhouse experiments revealed that the application of PMFs on corn had significant effect on fresh and dry weights of shoot and root, and the concentration and content of phosphorus in the root and shoot of corn. The measured parameters in treatments P. agglomerans P5, Pseudomonas sp. C16-2O, Enterobacter sp. S16-3, P. fluorescens and P. putida were significantly higher than control. Although, P5 strain had highest mean in all measured parameters among bacterial strains used in this study, but we introduce new isolated bacteria (S16-3 and C16-2O) along with P5 for further researches. Overall, the two bacteria Enterobacter sp. S16-3 and Pseudomonas sp. C16-2O can be considered because of their positive effects on corn growth [44 and 42% increase in shoot dry weight (SDW) and 1.60- and 1.39-fold increase in root dry weight (RDW), respectively] and P nutrition uptake (both 68% increase in SDW and 1.87- and 1.62-fold increase in RDW, respectively). [ABSTRACT FROM AUTHOR]

The present study was carried out to investigate biochemical responses of marigold (Calendula officinalis L.) to Bio-organic fertilizers. Effects of co-inoculation of two plant growth-promoting rhizobacteria (PGPR) (Azotobacter sp.145PI and Azospirillum sp.AC49I), humic acid (HA) (10 kg ha-1), vermicompost (VC) (7 T ha-1) and combinations of these treatments were evaluated in two marigold cultivars [Isfahan double flower (DF) and single flower (SF)]. The biosynthesis of leaf protein, soluble and insoluble carbohydrate contents were increased in treated plants, while total free amino acid content was not influenced by treatments. Fertilizers also had positive impact on leaf and flower pigments, total flavonoid content, and total phenolic contents. Maximum amounts of anthocyanins were obtained in the DF cultivar treated by VC+PGPR and VC, which were 11.414 and 11.192 µmol g-1 FW, respectively. The SF cultivar treated by PGPR (36.11 %) and also the same cultivar treated by VC (33.39 %) had the highest antioxidant activities. In general, simultaneous application of fertilizers and also vermicompost were recognized as the best treatment for marigold plants. In conclusion, the findings of the current study confirmed that chemical composition and antioxidant activity of marigold can be positively influenced by Bio-organic fertilizers; therefore they can be used to obtain medicinal plants with improved quality during sustainable agricultural practices. [ABSTRACT FROM AUTHOR]

Plant growth-promoting bacteria recover the negative effects of osmotic stress on canola. For comprehending the role of bacteria in canola under osmotic stress, Sarigol and Hyola308 as drought-sensitive and -tolerant cultivars, respectively, inoculated with Enterobacter sp. S16-3 as plant growth-promoting bacteria were treated with polyethylene glycol. Bacterial inoculation increased the root volume of Hyola308 under osmotic stress. Using a gel-free/label-free proteomic technique, 115 commonly changed proteins were identified in the root between inoculated Sarigol and Hyola308 under osmotic stress. In both cultivars with bacterial inoculation, proteins related to protein metabolism, cell organization, and signaling were increased in roots under osmotic stress. On the other hand, bacterial inoculation increased and decreased the abundance of malate dehydrogenase (EC 1.1.1.37) in roots of Hyola308 and Sarigol, respectively, under severe osmotic stress. Furthermore, in leaf, bacterial inoculation increased the abundance of tricarboxylic acid cycle-related proteins in Hyola308 under severe osmotic stress. These results suggest that bacterial inoculation might increase the tolerance to severe osmotic stress by modifying proteins related to energy metabolism in both leaf and root. Enhancement of energy metabolism elicited by bacterial inoculation might provide a connection between cell metabolism and root growth, which might cause regulated growth and increased tolerance in drought-tolerant canola under osmotic stress. [ABSTRACT FROM AUTHOR]

Introduction: Phosphorus and potassium are major essential macronutrients for biological growth and development. Application of soil microorganisms is one approach to enhance crop growth. Some bacteria are efficient in releasing K and solubilizing P from mineral sources but their behavior was not studied more in presence together. Materials and methods: In this study the ability of seven bacterial strains, including Pseudomonas putida P13, P. putida Tabriz, P. fluorescens Tabriz, P. fluorescens Chao, Pantoea agglomerans P5, Azotobacter sp. and Bacillus megaterium JK3 to release mineral K from muscovite and biotite with application of insoluble (Ca3(PO4)2) or soluble (Na2HPO4) P-sources was investigated. Nutrient Broth was used to prepare an overnight culture of bacteria to inoculate in Aleksandrov medium, which was used to study the dissolution of silicate minerals. It should be mentioned that Aleksandrov medium was used to determine the amount of released P from tricalcium phosphate (TCP) while muscovite was added to the medium as a sole source of potassium. Concentration of P was determined spectrophotometrically by ammonium-vanadate-molybdate method and K was determined by flame photometry. Results: The insoluble P-source led to a significantly increased released K into assay medium (66%), and the net release of K from the biotite was significantly enhanced. Among bacterial strains, the highest mean of released K was observed with P. putida P13 which released more K (27%) than the control. The amounts of released K from micas in the presence of insoluble and soluble phosphate by P. putida P13 were 8.25 and 4.87 mg/g, respectively. Discussion and conclusion: Application of insoluble phosphate could increase K release from mica minerals. The enhanced releasing of mineral K might be attributed to the release of organic acids from the bacteria, a mechanism which plays a pivotal role in solubilizing phosphate from inorganic source of phosphate. [ABSTRACT FROM AUTHOR]