Effects of plant growth promoting rhizobacteria on salinity tolerance of ornamental ‎cabbage (Brassica oleraceae L. cv. Kamome)‎

In order to study the morphologies and biochemistry of ornamental cabbage under salt stress, a factorial experiment was carried out based on completely randomized design in three replications. The treatments included salinity at three levels (4 and 8 dS.m-1 and control (no salinity) and growth stimulating bacteria at three levels (no inoculation Pseudomonas putida and Bacillus subtilis). Plant growth characteristics, including plant height, number of leaves, fresh and dry weight of leaves, fresh and dry weight of plant and root, showed a significant decrease compared to the control treatment with increasing salinity stress, and inoculation with growth-promoting bacteria, especially Pseudomonas putida, improved these attributes. Antioxidant activity and total phenol increased with increasing salinity, so that the highest amount of phenol and antioxidant was observed at treatment 8 dS/m (1.08 mg/g FW and 62.52 μmol/g FW, respectively). On the other hand, the use of Bacillus bacteria could increase the amount of total phenol and antioxidants in contrast with salinity (1.08 mg/g FW and 62.78 μmol/g FW). The amount of proline in leaves also had an increasing trend at different levels of salinity stress, and its highest level was observed at the highest level of salinity stress and the application of Bacillus subtilis bacteria. The interaction between bacteria and salinity stress reduced the accumulation of sodium element and increased the amount of potassium element. The results of this experiment showed that growth-promoting bacteria, especially Pseudomonas putida bacteria, reduce the damage caused by salt stress in ornamental cabbage plants.