The role of mycorrhizae and plant growth promoting rhizobacteria (PGPR) in improving crop productivity under stressful environments.

https://www.uv.mx/personal/tcarmona/files/2010/08/Miransari-y-Smith-2014.pdf

Plant hormones and seed germination

A biocontrol Streptomyces isolate (C) was tested for its plant growth promoting qualities under saline conditions. Exposure to elevated osmotic strengths up to 300 mM NaCl increased dry weight and cfu/ml significantly. The isolate C produced indolyl-3-acetic acid (IAA) into the medium in the amount of 2.4 μg/ml. The amount of auxin increased after adding salt and reached to 4.7 μg/ml in 300 mM NaCl. Biosynthesis of siderophore was detectable and increased in presence of NaCl. Streptomyces isolate C showed good solubilization of tricalcium phosphate in culture medium with 92 mg/l. Solubilization decreased in presence of NaCl. Soil treatment with isolate C increased the growth and development of wheat plant in normal and saline conditions. In this treatment there were significant increases in germination rate, percentage and uniformity, shoot length and dry weight compared to the control. Applying the bacterial inocula increased the concentration of N, P, Fe and Mn in wheat shoots grown in normal and saline soil, but had non-significant effect on other micro and macronutrients concentrations. Results of this study show that Streptomyces isolate C has potential to be utilized as biofertilizer in saline soils.

Plant growth promoting activity of an auxin and siderophore producing isolate of Streptomyces under saline soil conditions

The soil environment is interesting and complicated. There are so many interactions taking place in the soil, which determine the properties of soil as a medium for the growth and activities of plants and soil microorganisms. The soil fungi, arbuscular mycorrhiza (AM), are in mutual and beneficial symbiosis with most of the terrestrial plants. AM fungi are continuously interactive with a wide range of soil microorganisms including nonbacterial soil microorganisms, plant growth promoting rhizobacteria, mycorrhiza helper bacteria and deleterious bacteria. Their interactions can have important implications in agriculture. There are some interesting interactions between the AM fungi and soil bacteria including the binding of soil bacteria to the fungal spore, the injection of molecules by bacteria into the fungal spore, the production of volatiles by bacteria and the degradation of fungal cellular wall. Such mechanisms can affect the expression of genes in AM fungi and hence their performance and ecosystem productivity. Hence, consideration of such interactive behavior is of significance. In this review, some of the most important findings regarding the interactions between AM fungi and soil bacteria with some new insights for future research are presented.

Interactions between arbuscular mycorrhizal fungi and soil bacteria

Plant growth promoting rhizobacteria (PGPR) can enhance plant growth by alleviating soil stresses. Although previously investigated, some new interesting details are presented regarding the alleviating affects of Azospirillum sp. on wheat growth under drought stress in this research work. We hypothesized that the isolated strains of Azospirillum sp. may alleviate the adverse effects of drought stress on wheat (Triticum aestivum L.) growth. Three different strains of Azospirillumlipoferum (B1, B2 and B3) were used to inoculate wheat seedlings under drought. During the flowering stage the seedlings were subjected to three drought levels with five different time longevity, including control. Pots were water stressed at 80% (S0), 50% (S1) and 25% (S2) of field capacity moisture in a 25 day-period. Soil and plant water properties including water potential and water content, along with their effects on bacterial inoculum and wheat growth, were completely monitored during the experiment. While stress intensity significantly affected bacterial population and wheat growth, stress longevity only affected wheat water potential and water content. Compared to uninoculated treatments strain B3 (fixing and producing the highest amounts of N and auxin, respectively, with P solubilizing and ACC-deaminase activities) increased wheat yield at S1 and S2 by 43 and 109%, respectively. However, strain B2 (producing siderophore) was the most resistant strain under drought stress. The results of this experiment may elucidate the more efficient strains of Azospirillum sp. for wheat inoculation under drought stress and the mechanisms by which they alleviate the stress.

Wheat (Triticum aestivum L.) growth enhancement by Azospirillum sp. under drought stress

Plant growth promoting rhizobacteria (PGPR) is referred to a heterogeneous group of beneficial rhizospherebacteria that could enhance plant yield through one or more mechanisms. Flavobacterium has been noted asPGPR in almost all review articles. However, there are a few studies regarding plant growth promotion imposedby them. Some of Plant growth promoting characteristics such as Phosphate solubilizing capacity, ability to useof 1-Amino Cyclopropan-1-Carboxylate (ACC) as sole nitrogen source and production of auxin, siderophore,salicylic acid, chitinase and hydrogen cyanide were evaluated in forty-four flavobacteria isolated fromrhizosphere of wheat. Results showed that none of the isolates were able to produce siderophore, salicylic acidand chitinase and they were not able to use ACC as well. Determining the siderophore showed that none isolatesdid not grow on Chrome Azurol S (CAS) Agar medium. The results of this part were further analyzed usingCAS Agar Diffusion (CASAD) method, but the results were also negative. HCN production was observed in allisolates, but in lowest limit. Thirty-four isolates were capable to solubilize insoluble inorganic Phosphate (P)sources. The average rate of P-solubilization was 3.54 ?g Pml-1, ranging from zero to 37.48 ?gPml-1. There wasa significant negative correlation (r = -0.81**) between solubilized P and the final pH of the growth medium. Inthis study, all the isolates were able to produce auxin, ranging from 0.27 to 12.03 ?gml-1 averaged by 2.03.Considering the ability of the isolates to produce auxin and for P-solubilization, it is necessary to evaluate theireffect on growth and yield of different crop plants.

/pdf/plant-growth-promoting-characteristics-in-some-5cfmn0nhr0.pdf

Plant Growth Promoting Characteristics in Some Flavobacterium spp. Isolated from Soils of Iran

Fluorescent pseudomonads are among the most influencing plant growth-promoting rhizobacteria in plants rhizosphere. In this research work the plant growth-promoting activities of 40 different strains of Pseudomonas fluorescens and Pseudomonasputida, previously isolated from the rhizosphere of wheat (Triticum aestivum L.) and canola (Brassica napus L.) and maintained in the microbial collection of Soil and Water Research Institute, Tehran, Iran, were evaluated. The ability of bacteria to produce auxin and siderophores and utilizing P sources with little solubility was determined. Four strains of Wp1 (P.putida), Cfp10 (Pseudomonas sp.), Wp150 (P. putida), and Wp159 (P. putida) were able to grow in the DF medium with ACC. Thirty percent of bacterial isolates from canola rhizosphere and 33% of bacterial isolates from wheat rhizosphere were able to produce HCN. The results indicate that most of the bacteria, tested in the experiment, have plant growth-promoting activities. This is the first time that such PGPR species are isolated from the Iranian soils. With respect to their great biological capacities they can be used for wheat and canola inoculation in different parts of the world, which is of very important agricultural implications.

Plant growth-promoting activities of fluorescent pseudomonads, isolated from the Iranian soils

Plant growth promoting rhizobacteria (PGPR) consisting a wide range of beneficial soil bacteria inhabiting rhizosphere of plant. Fluorescent pseudomondas are the most important plant growth promoting rhizosphere bacteria in different crop plants. In this research, twenty-five isolates of fluorescent pseudomonads isolated from forty soil samples of wheat rhizosphere and forty four isolates of Flavobacterium selected from the bacterial strains collection were employed. The ability of these isolates for production of chitinase, Salicylic acid, siderophore and hydrogen cyanide and antifungal activity against Rhizoctonia solani were determined. Results revealed that all the fluorescent pseudomonads isolates were able to produce siderophore on Chrome Azurol S (CAS) agar plates and siderophore is an important secondary metabolite in plant growth promotion and antifungal activity. In CAS agar method, the range of siderophore production was 0.34-1.21 halo diameter per colony diameter. None of these isolates were capable for chitinase production. Salicylic acid (SA) production by the isolates ranging from 0-10.91 g.ml -1

/pdf/evaluation-of-biological-control-traits-in-some-isolates-of-22pdqpcmo1.pdf

Evaluation of Biological Control Traits in Some Isolates of Fluorescent Pseudomonads and flavobacterium

Unfortunately, the family name of the co-author P. Abbaszadeh-Dahaji was incorrectly published in the original publication and corrected by this correction.

/pdf/correction-to-plant-growth-promoting-activities-of-przj24dn13.pdf

Hadi Asadi-Rahmani

Papers

Plant Growth Promoting Characteristics in Some Flavobacterium spp. Isolated from Soils of Iran

Plant growth-promoting activities of fluorescent pseudomonads, isolated from the Iranian soils

Evaluation of Biological Control Traits in Some Isolates of Fluorescent Pseudomonads and flavobacterium

Correction to: Plant growth-promoting activities of fluorescent pseudomonads, isolated from the Iranian soils