Isolation and evaluation of plant growth promoting indices of Pseudomonas fluorescens isolated from Pistachio rhizosphere

Document Type : Research Paper

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Pseudomonas fluorescens bacteria are the most important plant growth promoting rhizobacteria that improve the growth and plant nutrition. The aim of this research was to isolate and evaluate the PGP indices of Pseudomonas fluorescens isolates from pistachio trees rhizosphere. Thirty four Pseudomonas fluorescens isolates were isolated from eighty rhizospheric soil samples from Pistachio orchards located in Rafsanjan provence. The ability of Siderophore production, auxin, HCN and dissolution potential of Ca3 (PO4)2, ZnO and ZnCO3 in solid and liquid medium of all isolates were evaluated. The results indicated that all isolates were able to produce sidrophore in CAS agar. The average production of sidrophore and the ratios of halo to colony diameter were 2.05 and 2.86 (belonged to the D9 isolate), respectively. Most of isolates (96.88%) were able to produce auxin at 100 ppm of L-tryptophan.  The highest amount of produced auxin was 16.64 µg/ml (D15 isolate). Evaluation of HCN production using the muncell color system showed that 75% of isolates were able to produce HCN and D24 isolate produced the maximum HCN. The results indicated that all Pseudomonas fluorescens isolates were capable of solubilizing Ca3 (PO4)2 in the solid and liquid PKV media. The highest amount of dissolved P was 705 µg/ ml and it was belong to D6 isolate. 75% and 48% of isolates were capable of solubilizing ZnO and ZnCO3 in a PKV liquid medium, respectively. The average dissolved Zn by Pseudomonas fluorescens isolates in liquid medium containing ZnO and ZnCO3 were 8.47 and 2.48 µg/ ml, respectively.  The highest amount of dissolved Zn from ZnO and ZnCO3 sources were 67.37 and 7.70 µg ml-1, (D14 and D25) respectively. The results also indicated that inoculation of pistachio seedlings with superior isolates increased the seedlings height, leaf area, shoot and root dry weights and concentrations of P, Fe, Zn, Mn and Cu in shoot significantly. According to the results, superior isolates can be used to provide an appropriate inoculum.
Journal of Sol Biology
Volume 2, Issue 2 - Serial Number 2
March 2015
Pages 173-186

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