E. Shirmohammadi; H.A. Alikhani; Ahmad Ali Pourbabaee; H. Etesami
Abstract
Introduction: Stresses of drought, salinity and deficiency of nutrients especially phosphorus (P) are the most important challenges for wheat production in Iran. One of the ways to achieve more wheat yield production is increasing of this plants tolerance to stresses of water-deficit, salinity and deficiency ...
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Introduction: Stresses of drought, salinity and deficiency of nutrients especially phosphorus (P) are the most important challenges for wheat production in Iran. One of the ways to achieve more wheat yield production is increasing of this plants tolerance to stresses of water-deficit, salinity and deficiency of essential elements such as P; and/or alleviate destructive effects of these stresses. In this respect, use of PGPR can be useful. Research has shown that PGPR with multiple mechanisms reduces the negative effects of water-deficit and salinity stresses, and also increases the resistance of plants to these stresses, which ultimately leads to increase of plants growth. This study was designed and carried out to investigate the effect of three superior PGPR on qualitative and quantitative indices of wheat under water-deficit stress in saline soil. Materials and Methods: The soil used in this experiment was collected from longitude of 49° 26' 25'' E, latitude of 35° 52' 26'' N and elevation of 1534 m (located in the Qazvin province of Iran) from depth of 0-30 cm of soil. According to the experimental design, 3.5 kg of soil with applying P-fertilizers treatments was filled to the pots. The factorial arrangement based on completely randomized design (CRD) was used in this study. The treatments were replicated three times. The first factor: soil water content at two levels including 80% and 55% FC (W80 and W55); the second factor: Bacterial inoculants at four levels including control or non-inoculated seeds with bacterium (B0), inoculated seeds with Bacillus pumilus strain W72 (B1), inoculated seeds with B. safensis strain W73 (B2), inoculated seeds with Staphylococcus succinus strain R12N2 (B3); and the third factor: P-fertilizers at six levels including control or non-treated plants with P-fertilizers (F0), and plants treated with (rock phosphate) RP - (F1), RP + 19 mg triple superphosphate (TSP) / kg of soil (F2), RP + 38 mg TSP / kg of soil (F3), RP + 57 mg TSP / kg of soil (F4), with 57 mg TSP / kg of soil (F5), generally there were 144 experimental units (pots). Also, 192 mg RP (containing 13.8% P2O5 or 6.13% P) was mixed per kg of soil in each of RP treatments. Statistical analysis of data was performed using SAS software and comparison of means was evaluated by using the Tukey's test (HSD) at p < 0.05 level. There were 5 plants in each pot and irrigated up to 80% FC with distilled water. With the beginning of stem elongation stage, water-deficit stress was applied and continued until the harvest. During the experiment, pots were kept in greenhouse at 25/20±2°C day/night temperatures and 16 h photoperiod with 23,000 lux light intensity. At the end of the experiment, plants height, fertile clusters, root dry weight /shoot dry weight ratio, total dry weight of plant, grain number, thousand grain weight, also, root, shoot and grain P-concentration were measured. Results and Discussion: Generally, it can be said that the moisture level of W80 compared to W55 increased all of measured traits in wheat plant. Due to the unique properties of water and its role in biological and non-biological reactions, by reducing soil water content to near of the permanent wilting point (W55), water absorption by the plant hardly occurs. Therefore, the plant needs to consume more energy for water absorption or grow with less water than normal status, which these factors disturb the metabolism of cells and eventually decreases natural activity and growth of plant. Also, it seems that under water stress condition, wheat plant by formation of “Rhizosheaths” around of their own roots, enters to the defensive phase and by this strategy prevents expansion of their own rhizosphere. With attention to the special importance of the rhizosphere in the supply of water, nutrients and activity of microorganisms, as well as the effect of microorganisms secretion and root exudates on the solubility and availability of nutrients. Thus, it is reasonable that qualitative and quantitative traits of plants decrease by reduction of the rhizosphere diameter due to the water-deficit stress. There was no significant difference between application of rock phosphate and control (F0) for most of measured traits of soil and plant; but, application of RP with bacterial treatments (B1 and B2 at W80 and B3 at both level of W55 and W80) compared to the control, often increased measured traits. Also, each level of TSP compared to the control, often increased this trait. Research indicates that RP can be used as a P-fertilizer, but its efficiency depends on its reactivity in the soil. There is ample evidence that RP has not enough efficiency in neutral and alkaline soils; but, it can be used as the P-fertilizer with proper efficiency in acidic soils or alkaline soil with application of PGPR. Often, all of three bacterial treatments (B1, B2 and B3) at level of W80 and B3 treatment at level of W55, compared to control (without bacterial inoculation) improved qualitative and quantitative traits of plant. Research also shows that under stressful and non-stressful conditions, PGPR can improve plant growth by different strategies. However, this microorganism does not always improve plant growth under all conditions. It seems to be due to differences in genetic and function of bacteria and with conditions change, each bacterium may behave differently. Conclusions In general, for wheat cultivation that may get exposed to moisture stress at one or more stages of its growth (such as dry-farming of wheat), the use of B3 bacterial inoculant (Staphylococcus succinus strain R12N2) seems appropriate for crop management. Because in this study at both W80 (non-water-deficit stress) and W55 (severe water-deficit stress) levels of soil water content, B3 treatment increased qualitative and quantitative of wheat traits. In other words, because of the natural conditions of the dryland farming, the probability of precipitation is different; it seems that B3 treatment can increase wheat production under these conditions. However, the use of this bacterium as a biofertilizer for dryland wheat farming in Iran or other place of the world requires further testing and evaluation in dryland farms of that countries.
Bahman Khoshru; Mohammad Reza Sarikhani
Abstract
Introduction: Application of chemical and organic carrier and its integration with useful microorganisms including phosphate solubilizing bacteria (PSB) has facilitatedproduction of phosphate microbial fertilizers (PMFs), which are used in granular or powder form. One of the major limitation of thesebiofertilizers ...
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Introduction: Application of chemical and organic carrier and its integration with useful microorganisms including phosphate solubilizing bacteria (PSB) has facilitatedproduction of phosphate microbial fertilizers (PMFs), which are used in granular or powder form. One of the major limitation of thesebiofertilizers is decline or loss of PSB viable cell in the granule preparation process. Accordingly, in this study, isolation of temperature resistant phosphate solubilizing bacteria was performed and temperature tolerance and ability to dissolve phosphate from rock phosphate (RP) and tricalcium phosphate (TCP) sources were evaluated.
Materials and Methods: Firstly, each soil samples incubated for 16 hours at 55 °C, then dilution series were prepared and 100 μl of four final dilutions (10-6, 10-7, 10-8, and 10-9) were used to spread on Sperber solid medium. After spreading the microbial suspensions from the dilutions in the Sperber solid culture medium and the appearance of colonies, screening based on the resistance to soil temperature treatment and, subsequently, the ability to grow in a solid Sperber solid medium and dissolution of low solubility phosphate (formation of transparent halo), was done to isolate PSB. In order toprepare PMF, each of screened PSB were cultured in NB, andthen 1 ml of overnight culture wasmixed with 9 ml sterile distilled water and added to the basal formulation of rock phosphate (45 g), bagasse (30 g) and sulfur (15 g) with initial temperature of20°C.Temperature treatments (55 °C for 16 hours) of bacteria were performed in three steps: a) on sampled soils, b) pure-culture of bacteria and c) bacteria added to the carrier. Microbial population in provided microbial fertilizer was countedin two ways a) half of the microbial fertilizer was kept at normal temperature by maintaining the initial conditions, b) another half after the temperature applied (55 ° C for 16 hours). The semi-quantitative and quantitative test of insoluble inorganic phosphate solubility was performed by isolates in solid and liquid Sperber medium. The 16S rRNA molecular method was used to identify the isolated bacteria by general primers 27F and 1492R.
Results and Discussion: Five bacteria (RPS4, RPS6, RPS7, RPS8, RPS9) out of nine isolated bacteria were able to solubilize mineral phosphate (TCP and RP) but only two isolates (RPS7 and RPS9) were resistant to temperature (55 °C for 16 h). In tricalcium phosphate medium, the RPS9 and RPS7 bacteria had a high ability to solubilize insoluble inorganic phosphate with average of 2.60 and 2.27 for a ratio of (HD / CD) after 12 days, respectively. There was no halo in Sperber medium containing rock phosphate. The amount of solution in the quantitative methods was also obtained to be 563.8 and 324.1 mg / l for RPS9 and RPS7 bacteria, respectively. The prepared microbial fertilizer was counted in two ways (a): half of the sample fertilizer was kept at normal temperature by maintaining the initial conditions; (b):after the maintaining temperature at 55 °C for 16 hours, the population of other half was determined. During counting the initial microbial population (zero time) at normal temperature, all bacteria used in microbial carrier had an acceptable population. During examining the populationsof microbial in the initial carrier, RPS4, RPS6, RPS7, RPS8 and RPS9 bacteria were 3.6, 3.5, 3.6, 3.5, 3.6 and 3.5 (×106 CFU/g), respectively. After 4 months the populations were 4.6, 6.3, 9.6, 7.4 and 8.6 (×105) and in the 6th month, the populations were 3.9, 3.8, 12.3, 4. 7 and 9.2 (×104) seeming to be favorable for the tested bacteria. It seems that this survival time for the tested bacteria is desirable. During countingactive population of temperature treated microbial fertilizers, the initial population of the microbial carrier (at zero time) decreased 10 times with respect to the non-treated carrier. Active population ofRPS9 and RPS7 (temperature-resistant treatments) in the zero time was 4.5 and 4.3 (×105), respectively. Although the RPS9 and RPS7 microbial populations were able to survive in non- temperature treatments for 6 months, it was observed that in the treatment, this viability practically reduced to 4 months. Molecular identification of the isolates RPS7 and RPS9 revealed that they belonged to Pantoeaagglomerans.
Conclusions: According to the findings of this research, using phosphate solubilizing bacteria and temperature resistant Pantoeaagglomerans RPS9, recently isolated and identified, can be considered toindustrially produce granular microbial fertilizers. It is worth mentioning thatfurther studies are required to be carried out on the effectiveness of this formulation with these bacteria infield scale.
Vida Hemmati; Hadi Asadi Rahmani; Shokofeh Rezaee
Abstract
Introduction: Wheat is one of the most important food crops. In modern agriculture, due to the increase in human population and the detrimental effects of pesticides such as environmental pollution, concerns about human and animal health, adapting suitable alternatives which have none of these dangerous ...
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Introduction: Wheat is one of the most important food crops. In modern agriculture, due to the increase in human population and the detrimental effects of pesticides such as environmental pollution, concerns about human and animal health, adapting suitable alternatives which have none of these dangerous effects would be necessary. This is possible by increasing the production of bio-fertilizers. Plant growth-promoting rhizobacteria (PGPR) are the beneficial rhizosphere bacteria that can enhance plant growth directly or indirectly through a wide variety of mechanisms. PGPR can stimulate plant growth directly by supplying nutrients such as phosphorous and nitrogen or by the production of phytohormones such as auxins, cytokinins (CK), gibberellins (GAs) or ACC deaminase synthesis. They can also promote plant development indirectly by the suppression of pathogens by different mechanisms such as biosynthesis of antimicrobial molecules or antibiosis induced systemic resistance (ISR), rhizosphere competition, cell wall degrading enzymes like chitinase and HCN production. In this study, amplified ribosomal DNA restriction analysis was performed for screening the bacterial isolates. Then phosphate solubilization, siderophore and auxin release activities and effect of bacterial isolates on wheat seed germination traits were studied.
Materials and Methods: In order to isolate wheat rhizosphere bacteria, soil samples were taken from the wheat rhizosphere of Tehran, Qazvin, Zanjan, West and East Azerbaijan, Kurdistan and Hamadan provinces. Genomic DNA of each isolate was extracted by using a modified cetyl trimethylammonium bromide (CTAB) method. Amplified ribosomal DNA restriction analysis with HpaII and RsaI restriction enzymes was done for genetic screening. Growth stimulating factors were evaluated by auxin production, siderophore production, and inorganic phosphate solubilizing activity. Siderophore production was determined by measuring the diameters of the colony (mm) and of any orange halo (mm) formed from the blue medium surrounding bacterial growth on CAS Blue Agar medium. To examine Pi solubilization capability, 2µ bacteria suspension was placed on the plates containing Sperber’s medium. Cultures were incubated at 25 ± 2 °, when the diameters of the colony and of the halo zone surrounding it were measured and the mean ± SE of the ratios of halo (mm)/colony (mm) calculated. In order to evaluate the production of auxin, isolates were grown in 100ml flasks containing 25ml TSB medium for 48h on a rotary shaker. 1 ml supernatant was mixed with 2ml of Salkowsky reagent after centrifugation at 10000g for 15min. The absorbance of the complex was read at 535nm in a Spectrophotometer. To investigate the effect of bacterial isolates on germination traits, radicle and plumule fresh and dry weight, radicle and plumule length, germination percentage, germination rate, and germination average rate were measured. The data were analyzed with using SAS 9.1. Mean comparisons were performed by LSD and main effective interaction was found significant at P < 0.05.
Results and Discussion: 20 isolates of wheat rhizosphere bacteria were subjected to amplified ribosomal DNA restriction analysis. The 16S rDNA region was amplified by polymerase chain reaction and PCR products were digested by HpaII and RsaI restriction enzymes. From each pattern, one sample was sent to sequencing. Different species including; Chryseobacterium ginsenosidimutans, C. lathyri, C. piperi, C. taiwanense, Novosphingobium aromaticivorans, Pedobacter duraquae, and Sphingomonas koreensis were identified from the wheat rhizosphere. Bacteria were tested for their plant growth promoting qualities. All of the strains produced auxin from 1.90 to 25.93. Mean comparison of the data showed that the highest level of auxin was produced with F1 and the lowest amount was observed by F18. Phosphate solubilization measured as a halo zone on Sperber’s medium was observed with F6 and F56 isolates. The ratio of the diameter of the halo zone to the colony diameter was 2.86 with F6. The highest level of siderophore production by wheat rhizosphere bacteria, observed as halo formation around colonies on CAS Blue Agar medium, was obtained with F46, followed by F45 and F3. The ratio of the diameter of the orange halo surrounding bacterial growth to the colony diameter was 2.86 with F46. The result showed that the effect of wheat rhizosphere bacteria on germination traits such as radicle fresh and dry weight, plumule fresh weight, radicle and plumule length, germination percentage, germination rate, and germination average rate was significant at the one percent level and the effect of wheat rhizosphere bacteria on plumule fresh weight was significant at the five percent level.
Conclusion: Plant growth promoting bacteria enhance the growth and development of plants with different ways. These bacteria affect the growth and development of crops by phosphate solubilization, production of hydrogen cyanide, siderophore, and hormones such as auxin, gibberellic acid and cytokinins. According to the result, due to growth promoting characteristics such as siderophore and auxin production, phosphate solubilization, and the improvement of the seed germination traits, it can be possible to prepare bacterial inoculant for the field experiment in order to increase the availability of nutrients and improve the growth of plants.
hamidreza boostani; mostafa chorom; abdolamir moezzi; najafali karimian; naimeh enayatizamir; mehdi zarei
Abstract
Introduction: Zinc (Zn) is an important nutrient element for humans and plants that controls many biochemical and physiological functions of living organisms. Zinc deficiency is common in high pH, low organic matter, carbonatic, saline and sodic soils. Salinity is a major abiotic environmental stresses ...
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Introduction: Zinc (Zn) is an important nutrient element for humans and plants that controls many biochemical and physiological functions of living organisms. Zinc deficiency is common in high pH, low organic matter, carbonatic, saline and sodic soils. Salinity is a major abiotic environmental stresses that limits growth and production in arid and semi-arid regions of the world. Bioavailability of Zn is low in calcareous and saline soils having high levels of pH and calcium. Desorption of Zinc (Zn) from soil as influenced by biological activities is one of the important factors that control Zn bioavailability. Few reports on the effects of salinity on the availability and desorption kinetics of Zn are available. Rupa et al. (2000) reported that increasing the salt concentration led to increase Zn desorption from soil due to ion competition on soil exchangeable sites. Different kinetic equations have been used to describe the release kinetics of nutrients. Reyhanitabar and Gilkes (2010) found that the power function model was the best equation to describe the release of Zn from some calcareous soil of Iran, whereas Baranimotlagh and Gholami (2013) stated that the best model for describing Zn desorption from 15 calcareous soils of Iran was the first-order equation.less attention has been paid to kinetics of Zn release by DTPA extractant over time by inoculation of plant growth promoting rhizobacteria and mycorrhizae fungi in comination with soil salinity.The objective of this study was to evaluate the effect of plant growth promoting rhizobacteria (PGPR) and mycorrhizae fungi (MF) inoculation on release kinetic of Zn in a calcareous soil at different salinity levels after in cornplantation
Materials and Methods: A composite sample of bulk soil from the surface horizon (0-30 cm) of a calcareous soil from southern part of Iran was collected, air dried, passed through 2 mm sieve, and thoroughly mixed. Routine soil analysis was performed to determine some physical and chemical properties. The experiment was conducted in the greenhouse of agriculture college of Shahid Chamran University, Ahvaz, Iran. A factorial experiment as a completely randomized design with three replications was conducted in greenhouse conditions. The first factor consisted of salinity levels (0, 15 and 30 cmol(c) kg-1 salt supplied as a 3:2:1 Na:Ca:Mg chloride salts) and the second factor was microbial inoculation (without inoculation, fungi, bacteria, bacteria + fungi).Soil samples were extracted using DTPA extractant for periods of 0.5, 1, 2, 6, 12 and 24 hours. Cumulative Zn released (q) as a function of time (T) was evaluated using seven different kinetic models. A relatively high values of coefficient of determination (r2) and low values of standard error of estimate (SEE) were used as criteria for the selection of the best fitted models. Statistical analysis of data was done using MSTATC package (Mstatc, 1991). Comparison between means was performed using Duncan's multiple range test (DMRT) at the significant level of P < 0.05. Also, charts were drawn by excel computer package.
Results and Discussion: Investigation of Zn release patterns showed that the control and all treated soils had a uniform pattern of Zn release. Overall, Zn release patterns were generally characterized by an initial fast reaction at first two hours, followed by slower continuing reaction. It seems likely that the release of zinc is controlled by two different mechanisms. Two-step process of releases (rapid and subsequent slow) is attributed to the existence of places with different energy. The use of all microbial treatments increased the initial release of Zn compared to control. The most and the least Zn initial release observed in fungi-bacterial and bacterial treatment respectively. By application of all microbial treatments, Zn release rate declined compared to control and the lowest decrease observed in fungal treatment. In general, Zn initial release was increased and Zn desorption rate was decreased by increasing of salinity levels. Also, soluble and exchangeable forms of Zn had the highest influence on Zn release control.
Conclusions: Results showed that simplified Elovich, two constant rate and parabolic diffusion kinetics models showed good description of the Zn release. Based on the highest correlation coefficient and the lowest mean standard error of the estimate, simplified elovich determined as the best kinetic model. So it seems that the main mechanism controlling the Zn release in the tested soil is diffusion phenomena.
