Detection of abiotic stress tolerant Azotobacter species for enhancing plant growth promoting activities

Detection of Azotobacter species AC9 was done for tolerance of high temperature and analysis of phosphate solubilizing activity, zinc solubilizing activity, hormone production activity and plant growth promoting traits on tomato seedlings. For heat stress tolerance assessment of the isolated strain, our experiment was designed to be suitable for the climate of our country. In this study, Azotobacter chroococcum was isolated from agricultural soil in Kyaukse province and identified by some biochemical characteristics and 16S rRNA sequencing. The isolated strain can tolerate high temperature up to 50 ̊ C. In phosphate solubilizing activity, the strain AC9 showed 183 µg/ml and 166 µg/ml at 5 days incubation period under normal and heat stress conditions respectively. AC9 also expressed highest IAA producing activity at 5 days incubation period for both normal and heat stress conditions. The highest IAA concentrations were 23.72 µg ml-1 (with 0.2% tryptophan), 55.55 µg ml-1 (with 0.5% tryptophan) and 17.73 µg ml-1 (with 0.2% tryptophan), 45.06 µg ml-1 (with 0.5% tryptophan) respectively. Under greenhouse condition, tomato plants inoculated with AC9 grew to a significantly greater extent than control plants.