Isolation and identification of plant growth-promoting bacteria from the rhizosphere of wheat and evaluation of their growth-promoting and biocontrol properties

Seed inoculation with endemic plant growth promoting rhizobacteria (PGPR) is a suitable approach in health management, improving the production and quality of agricultural products. The purpose of this research is to isolate and identify plant growth enhancing bacteria from the rhizosphere of wheat plants in Selseleh city (Iran) and to evaluate the beneficial characteristics of bacterial isolates.  The screening of PGPR isolates was done using tests of the ability to produce indole acetic acid (IAA), siderophore, protease, bacterial swarming  motility, biofilm formation, phosphate solubility and investigating the effect of bacterial isolates on wheat seeds germination in laboratory conditions. Among the 100 bacterial isolates extracted from the soil around the rhizosphere of wheat, the best four isolates were selected. The superior isolates were identified based on their morphological and biochemical characteristics as well as the nucleotide sequence of the 16sDNA region as Pseudomonas sp., Pseudomonas brassicacearum, Exiguobacterium sp and Acinetobacter calcoaceticus. In this research, Pseudomonas sp. strain has the highest IAA production (5.59 µg ml-1), siderophore production (2.35 cm), protease production (1.7 cm) and phosphate dissolution (390 µg ml-1) among four bacterial isolates. The highest percentage of inhibiting the growth of pathogenic fungus Fusarium graminearum, the cause of Fusarium blight disease of wheat spike, was related to P. brassicacearum isolate, which was evaluated as 49.33%.