جستجوی مقالات مرتبط با کلیدواژه "ریزوباکتری های محرک رشد گیاه" در نشریات گروه "آب و خاک"

Fluorescent Pseudomonads bacteria are one important group of the most important beneficial rhizobacteria that increase the growth of many plants due to having plant growth promoting (PGP) properties.

This research was carried out to screen 15 Fluorescent Pseudomonads isolates bacteria, isolated from rhizosphere soil of dry farming wheat, in terms of PGP traits such as 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase, indole-3-acetic acid (IAA), siderophore, solubilization of inorganic insoluble phosphates (Tricalcium phosphate: TCP) and hydrogen cyanide (HCN) (under non-saline and saline conditions), salinity resistance, drought resistance using polyethylene glycol (PEG6000) (with osmotic potentials of ─5, ─10 and ─15 bar).

All 15 isolates had the ability to grow at different drought levels. At the salinity levels of 4 and 10% sodium chloride (NaCl), only 10 and two isolates had the ability to grow. All of these isolates also had the ability to solubilize TCP and produce ACC deaminase, IAA, and siderophore, while nine isolates were positive for producing HCN. In the presence of salinity of 4% NaCl, all isolates were able to solubilize TCP, while only 8, 13, 6, and 4 isolates were able to produce ACC deaminase IAA, siderophore and HCN, respectively.

Considering the fact that a considerable amount of Pseudomonas fluorescent isolated from rhizosphere of wheat in this study were able to grow well in salinity of 4%, and also the studied bacteria at different levels of drought stress, in osmotic pressure of -15 Bar or 37.62% polyethylene glycol (PEG 6000) were able to grow. In addition to salinity and drought resistance, these bacteria were able to produce plant growth promoting components (PGPs) in the presence and absence of salinity. Specially, the results of this study showed that some native isolates of the dry farming soils of the country were able to produce the ACC-deaminase enzyme, but this ability was significantly reduced (46.6%) in salinity stress (4% sodium chloride salt) and even in some isolates the production of this enzyme was stopped. Therefore, based on the results of this study, it can be concluded that wheat rhizosphere soil of dry farming can be a suitable source for isolating Pseudomonas fluorescent bacteria, some of which have been able to maintain their growth stimulants in the presence of salt. Since, in dry conditions, the use of chemical fertilizers increases soil salinity twice, the use of such bacteria (phosphate solubilizing Pseudomonas) can reduce some of the limitations of wheat production in dry farming. However, their application as bio-fertilizer requires more greenhouse and field tests.

Plant inoculation with effective plant growth promoting and heavy metal resistant rhizobacteria is an efficient method to improve the phytoremediation efficiency and extraction of heavy metals from contaminated soils. With respect to this reason, astudy was conducted to isolate, identify and evaluate the growth stimulating traits of copper-resistant bacteria from a Cu-contaminated soil. Six rhizospheric soil samples of indigenous plants were collected in Sarcheshmeh Khatoonabad, Kerman province. After screening, six strains were selected. Phenotypic, biochemical and genetic identification data showed that five and one isolates were belong to Pseudomonas and Bacillus genera respectively. Then, the minimum inhibitory concentration of copper, siderophore production, auxin and hydrogen cyanide production, the ability to solubilize mineral phosphate in solid and liquid medium, the ability to solubilize Zn low soluble compounds in solid and liquid medium and production of ACC-deaminase were investigated. The results indicated that all of the isolates were resistant to various concentrations of copper. The maximum resistance to inhibitory concentration of copper was related to K4 and K5 strains at a concentration of 400 mg L-1 of copper. All of the strains were able to produce siderophore in CAS medium except for K6 strains and strain K5 was also the superior in siderophore production. Among the strains, K4 and K6 were not able to produce auxin. There was also a significant difference between auxin productions by isolates K1 with the other isolates, with the highest auxin production (2.07 mg L-1). The results also demonstrated that among the strains, only K4 strain was capable of producing hydrogen cyanide (degree: four=relatively high) and the other isolates were reported as non-production of hydrogen cyanide (degree: one). The results of Three Calcium Phosphate (TCP) solubilizing by isolates in PKV broth medium showed that K1, K2, and K3 strains had the most phosphorus solubility (706, 661 and 588 mg L-1) respectively and there wasn’t significant difference between them. The results demonstrated that K4 and K5 isolates with 0.910 and 0.850 halos to colony diameter had a significant difference with other isolates in solid medium containing ZnCO3 and the rest of the strains, K1, K2, K3 and K6 did not show the ability to solubilize the zinc carbonate as well. The solubilizing of solid zinc oxide in solid medium by K4 strain (halo:colony, 2.11) was the highest solubility of zinc oxide and K1, K2, K3 and K6 strains were not able to dissolve the zinc oxide in the solid medium. They did not show the ability to dissolve the low soluble zinc oxide nor the zinc carbonate compounds. K4 strain had the highest zinc carbonate solubility in the broth (12.5 mg L-1) and the highest solubility of zinc oxide in the broth was attributed to K4 strain (9.76 mg L-1). According to the results, these isolates can be used for enhancing phytoremediation efficiency of this element in contaminated soils.

In order to study the effect of Synorhizobium meliloti on growth and nutrients uptake of sesame, a greenhouse test was carried out. The first isolates investigated in IAA and siderophore producing and their ability in solubilizing inorganic phosphates. The results showed that all of isolates were able to produce auxin with different among. The maximum amount of IAA production was 59.5 g ml-1 that was related to SR24 isolate. All isolates could solubilize tricalcium phosphate (Ca3(PO4)2) in Sperber medium, and SR18 with 139 µg ml-1 had the highest ability to solubilize tricalcium phosphate. Also SR3 and SR32 isolates produced the highest amont of siderophore. According to the results, five isolates that were better in IAA and siderophore producing and solubilizing inorganic phosphates were selected and used in a greenhouse test. This experiment was conducted base on completely randomized design with five treatment including four isolates of Synorhizobium meliloti and one treatment without bacteria as control and four replications. The results indicated that inoculation of isolates enhanced Sesame shoot dry weight compared to control and this increasing was significant for SR18, SR16 and SR3. Application of most isolates also increased measured nutrients uptake in Sesame shoot. However only isolate SR18 significantly increased the nutrients uptake including P, Zn, Cu and Fe compared to control.