The effect of Azotobacter on some physiological and biochemical indicators and the expression of some effective genes in Ocimum basilicum under salt stress

Creating resistance to salinity in plants is a special feature for agriculture, because soil salinity is one of the limiting factors for growth. Plant growth stimulating bacteria moderate the effects of environmental stress in plants with different mechanisms. In accordance, a factorial greenhouse experiment was conducted in the form of a completely randomized design in three replicates. The experimental treatments included salinity (0, 100, 150, and 200 mmol sodium chloride) and Azotobacter bacterium which were performed on Ocimum basilicum. The results showed that salinity stress treatment by inoculating the plant with Azotobacter, dry and wet weights of the plant were increased (20%) compared to the condition without bacteria, in different concentrations of salinity. In salinity treatment, in the absence of bacteria, the amount of proline (48.6%) and the activity of antioxidant enzymes, catalase (0.059 units), peroxidase (0.263 units) and superoxide dismutase (7.6 units) increased in the plant. It was observed that the use of bacteria along with salt stress decreased the activity of antioxidant enzymes and proline. At all times, salinity stress increased the expression of DRB2 and p5cs genes, and this increase was the highest at 72 hours. At the same time, the use of bacteria with stress decreased the expression of the studied genes. The results of the study show the high effectiveness of treatment with Azotobacter in reducing the effects of salinity stress, antioxidant activity and increasing the expression of genes involved in stress control in Ocimum basilicum, and these effects can be investigated in other plants.