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To reduce negative effects of drought on plants, the use of plant growth- promoting rhizobacteria (PGPR) is an effective way to investigate that. The aim of the present study was to assess the bacterial characteristics Bacillus subtilis, Bacillus cereus, Pseudomonas koreensis, Pseudomonas fluroscence, and Enterobacter cloacae as growth, IAA production, phosphate solubilization, seed germination under different concentrations of polyethylene glycol (PEG 6000), and their efficacy of single or dual inoculation with two superior strains in lyzimeter experiment for improving growth and yield of sensitive variety of wheat (Triticum aestivum L.) cv. Sids 1 under different stress irrigation water 100, 70 and 35% of field capacity. Among the tested strains only 2 strains B. subtilis and P. koreensis showed a stable growth even in the maximum 40% PEG concentration. Also, P. koreensis produced the highest amount of IAA (1.84 µg ml-1), and solubilise maximum amount of P (1.59 µg ml-1), and improved seed germination at 30% PEG concentration. On the other hand, in gnotobiotic sand system experiment, PGPR increase growth dynamics as well as proline content and root colonisation of wheat plants over uninoculated control under drought-stressed conditions.
In lyzimeter experiment, single and dual inoculation treatments showed a significant increase of physiological and biochemical parameters of the plant under different drought stress treatments. Also, maximum increase 29.08 % in ascorbate peroxidase and 27.38% in catalase activities due to dual inoculation treatments T12 (Inoculation with B. subtilis + P. koreensis and irrigated at field capacity 35%), with respect to the corresponding unstressed control T10 (Inoculation with B. subtilis + P. koreensis and irrigated at field capacity 100%). Also, significant increase in grain yield, straw yield, biological yield and harvest index were observed under different drought stress. These results may be related to increase uptake of water and nutrients in wheat plant and reflected in better plant growth and yield.