Comparison of the Effectiveness of Plant Growth Promoting Bacteria and Chemical Fertilizers on Improving Growth and Yield of Wheat

Currently, the excessive application of chemical fertilizers in agriculture field is under debate due to environmental concerns. Therefore, it is important to find the alternative strategies to reduce harmful effects of farming practices. Aims of the research was to investigate the potential of rhizosphere and endophytic bacterial isolates isolated from the roots of wheat plant in terms of plant growth promoting (PGP) traits and study their effect on the wheat plant growth indices and decreased phosphorus (P) fertilizer use. To this end, the isolated bacteria were first screened for the production of indole-3-acetic acid (IAA) in the presence of tryptophan in the culture medium, and then the bacteria were tested for their ability to dissolve inorganic and organic phosphates. Then, the ability of these bacteria to improve wheat plant growth was conducted in a completely randomized design under greenhouse condition. Rhizospheric isolate R185 and endophyte isolate E240 produced 299.2 and 330.1 μg / ml P respectively and also produced 19.2 and 22 μg / ml IAA, respectively. 16S rRNA sequencing showed that these bacterial isolates were Pseudomonas. The results obtained from pot assay showed that the combined use of the strains caused a significant increase in wheat growth and nutritional indices (an increase of 55.6% in the amount of plant P) compared to their single application (35.6 and 36.4% increase in plant P content by R185 and E240, respectively). Among the cultivars evaluated, Roshan cultivar had a higher percentage of P (4.7%) and biomass (14.2%) than Marvdasht cultivar.