The role of microbial activity on iron uptake of wheat genotypes different in fe-efficiency

Soils in many agricultural areas have high pH, resulting in low availability of Fe. Wheat grown on such soils suffers from most micronutrient deficiencies, in particular Fe deficiency. The objective of this investigation was to determine the potentials of indigenous fluorescent Pseudomondas for siderophore production and their effects on 59Fe acquisition. For this purpose, some strains of Pseudomonas putida, Pseudomonas fluorescens, and Pseudomonas aeruginosa were isolated from different locations representing rhizosphere of wheat. The potentials of these strains for siderophore production were evaluated by chrome azorel-S assay (CAS blue agar) through color change. High siderophore producing Super-strains were selected for extraction of siderophores. These isolates were grown in SSM (standard succinate medium) for 72 hr at 28 C. Bacterial cell were removed by centrifugation (10000 g for 20 min) and the supernatant was filtered through filter membrane (0.22 ) and used as crowd siderophore. Evaluation of Fe uptake and translocation were carried out with complexes of bacterial siderophores and 59Fe compared with standard sierophore Desferrioxamine (DFOB) in randomized complete block design with three replications. This experiment was conducted on two wheat genotypes different in Fe-efficiency at hydroponic condition. The results showed that among the three most effective siderophores producing strains considered, the P. putida produced a sidrophore complex that showed efficiencies of 76 %, compared with the standard siderophore (DFOB) in the uptake of Fe and was statistically in the same group as the control. The effect of bacterial siderophores in the uptake of labeled 59Fe by wheat became significant, indicating that the chemical structure of the siderophores from different strains were different. The effects of wheat genotype in 59Fe activity of shoots was also significant, where the efficient Tabasi genotype contained 46 % more Fe in shoots than the inefficient Yavarous genotype. It was concluded that the siderophore complex from P. putida was the most effective in translocating Fe to shoots, particularly in efficient Tabasi genotype. Siderophore effectiveness in Fe availability decreased in the order; Sid-DFOB> Sid-putida>Sid-fluorescens> Sid-areuginosa

Effect of Biochar and Microbial Inoculation on P, Fe, and Zn Bioavailability in a Calcareous Soil

To identify effective ways of increasing the yield of crops grown in nutrient-poor calcareous soils, the combined effects of biochar addition and inoculation with plant growth promoting rhizobacteria (PGPR) and arbuscular mycorrhizal fungi (AMF) on wheat growth and soil properties were investigated under rhizobox conditions. Measured soil properties included pH, electrical conductivity (EC), organic matter content (OM), the availability of P, Fe, and Zn in the rhizosphere, and the uptake of these elements by plants. Combined biochar addition and microbial inoculation were shown to significantly increase the concentration of available forms of P, Fe, and Zn in the soil when compared to non-biochar treatments. The highest soil pH (7.82) was observed following biochar addition without microbial inoculation. The EC following biochar addition and PGPR inoculation was significantly higher than the other treatments, and the soil OM content was highest when combining AMF inoculation with biochar addition. The available P content after AMF inoculation combined with biochar addition was 27.81% higher than the control conditions, and AMF inoculation increased Fe and Zn bioavailability by factors of 2.38 and 1.29, respectively, when combined with biochar addition relative to AMF inoculation alone. The simultaneous biochar addition and PGPR inoculation significantly increased P uptake by the plants. The highest shoot Fe and Zn uptake rates were observed after a simultaneous application of biochar and PGPR inoculation. Under these conditions, shoot uptake was higher than seen when combining biochar addition with AMF inoculation by factors of 1.64 and 1.21, respectively. In general, it can be concluded that combining inoculation with growth-promoting bacteria and biochar addition can effectively improve nutrient availability to plant and soil conditions

Improving Phosphorus Availability and Wheat Yield in Saline Soil of the Lake Urmia Basin through Enriched Biochar and Microbial Inoculation

To reduce requirements for conventional chemical fertilizer and alleviate salinity stress in soils, a glasshouse experiment was conducted to assess the effects of enriched biochar on phosphatase activity, microbial respiration and wheat yield in non-saline and saline soils from the Lake Urmia basin (electrical conductivities 2 dS.m(-1) and 15 dS.m(-1), respectively). Nine treatments were tested: control, 1:1 mixture of apple and grape biochars (BC), phosphate solubilizing bacteria (PSB), BC plus PSB (BC-PSB), BC plus rock phosphate (BC-RP), BC enriched by rock phosphate and bacteria (BC-RP-PSB), BC enriched by rock phosphate and HCl (BC-RP-HCl) or H3PO4 (BC-RP-H3PO4) and chemical fertilizer (TSP). The addition of enriched biochar decreased the soil pH (by 0.5-0.9 units) and increased available phosphorus (>7-fold). In both the saline and non-saline soils, the highest alkaline phosphatase activity was obtained for BC-H3PO4-RP and BC-HCl-RP. Wheat growth parameters were reclaimed after enriched biochar application, indicating superior dry matter yields compared to the control and non-enriched biochar treatments and significantly higher yields compared to TSP. Beneficial effects on soil pH, phosphatase activity, soil respiration and biomass yield demonstrated that enriched biochar could partly substitute chemical fertilizers and increase plant growth in salt stress conditions. However, further field studies are needed to understand the benefits of enriched biochar in different soils and climates

The effect of PGPR inoculation on the growth of wheat

Many agricultural soils of Iran have high pH, resulting in low availability of Fe and Zn. The potentials of nonsymbiotic plant growth-promoting rhizbacteria (PGPR) for stimulating plant growth have been extensively used during recent decades. This experiment was carried out in growth chamber to evaluate the effects of siderophoreproducing Pseudomonads on the growth as well as Fe and Zn uptake of wheat. A randomized complete block design experiments was conducted using with Alborz genotype (an efficient phytosiderophore-producing bread wheat) treated with either 7NSK2 strain as a siderophore positive (sid+) or with MPFM1 mutant strain of the same isolate as a siderophore negative (sid-) treatments with three replications. The potentials of these strains for auxin production and phosphate solubilizing activity were evaluated by standard methods. The results showed that inoculation with sid+ strain increased dry matter production in shoots as compared with the control (sterile condition) or with sid - strain. Likewise, the concentration of chlorophyll a in leaves of sid+ and sid - treatments were 1.27 and 0.41 g mg-1 of fresh weight, respectively, and the concentration of chlorophyll b were measured to be 1.09 and 0.35 g mg-1 of fresh weight, respectively, indicating significantly more chlorophyll formation due to inoculation with sid+ as compared with sid -. The uptake of Fe by roots and its rate of translocation to the shoots were greater for the sid+ treated plants as compared with the sid - treated ones, indicating that siderophores increased the rate of Fe uptake by wheat. The effect of microbial inoculation on shoot Zn was not significant, but increased the concentration of Zn on roots compared with control. The results suggested that the siderophores of Pseudomonads may involve on increasing bioavailability of iron

Impact of chlortetracycline and sulfapyridine antibiotics on soil enzyme activities.

Pharmaceutical antibiotics are frequently used in the livestock and poultry industries to control infectious diseases. Due to the lack of proper guidance for use, the majority of administrated antibiotics and their metabolites are excreted to the soil environment through urine and feces. In the present study, we used chlortetracycline and sulfapyridine antibiotics to screen out their effects on dehydrogenase, alkaline phosphatase and urease activity. Factorial experiments were conducted with different concentrations of antibiotic (0, 10, 25 and 100 mg kg-1 of soil) mixed with soil samples, and the enzyme activity was measured at intervals of 1, 4 and 21 days. The results show that the chlortetracycline and sulfapyridine antibiotics negatively affect the dehydrogenase activity, but the effect of sulfapyridine decreases with time of incubation. Indeed, sulfapyridine antibiotic significantly affect the alkaline phosphatase activity for the entire three-time interval, while chlortetracycline seems to inhibit its activity within 1 and 4 days of incubation. The effects of chlortetracycline and sulfapyridine antibiotics on urease activity appear similar, as they both significantly affect the urease activity on day 1 of incubation. The present study concludes that chlortetracycline and sulfapyridine antibiotics have harmful effects on soil microbes, with the extent of effects varying with the duration of incubation and the type of antibiotics used

Potential of indigenous microbes as helping agents for phyto-restoration of a Pb-contaminated soil

The aim of this study was to assess the effects of heavy metal tolerant soil microbes inoculation on growth and metal uptake of pearl millet, Pennisetum glaucum, couch grass,Triticum repens and alfalfa,Medicago sativa in a soil spiked (and subsequently aged) with increasing concentrations of Pb. A soil sample (soil 1) was spiked with increasing (0 to 1500 mg/kg) concentrations of Pb and incubated for a seven months period. Another soil sample with a historical background of metal contamination (soil 2), having heavy metals-resistant microbial communities, also was taken and used as inocula. The plants were grown in pots containing contaminated soils. At the end of growth period, plants shoots were harvested, washed, oven-dried, ground and analyzed for Pb. The results showed a significant reduction (p < 0.05) in plants yield by increasing soil Pb concentration and inoculation of stress-adapted microbes further increased this reduction. This could be attributed to the increased access of plants to the relatively immobile Pb existed in the studied calcareous soil as well as to more metal contaminant absorption caused by soil microbial activity. In general, introduction of the microbes also resulted in lower Pb uptake by the studied plants

Interactions between Biochar and Compost Treatment and Mycorrhizal Fungi to Improve the Qualitative Properties of a Calcareous Soil under Rhizobox Conditions

Most calcareous soils have relatively low levels of organic matter. To evaluate the effect of pruning waste biochar (PWB) and pruning waste compost (PWC) combined with arbuscular mycorrhizal fungi (AMF) on the biological indices, a rhizobox study on wheat using a completely randomized design was conducted under greenhouse conditions. The studied factors included the source of organic material (PWB, PWC, and control), the microbial inoculation (+AMF or -AMF), and the zone (rhizosphere and non-rhizosphere soil). At the end of the plant growth period, organic carbon (OC), microbial biomass carbon (MBC), microbial biomass phosphorous (MBP), microbial respiration (BR), substrate-induced respiration (SIR), and alkaline (ALP) and acid (ACP) phosphatase enzyme activities in the rhizosphere and non-rhizosphere soils were determined. Simultaneous application of a source of organic matter and AMF inoculation significantly increased the OC and biological indices of soil relative to those observed when applying organic matter without AMF inoculation. Additionally, MBC, MBP, ACP, and ALP enzymes activities in the rhizosphere zone were significantly higher than in the non-rhizosphere. AMF increased BR and SIR levels in the rhizosphere by 13.06% and 7.95% compared to those in the non-rhizosphere, respectively. It can be concluded that PWC and PWB can improve soil biological properties by increasing microbial activity