Influence of bacterial biofertilizer on morphophysiological indicators of mustard under salt stress

Bacterial fertilizers are an effective technology for growing crops under saline conditions. The effect of biofertilizer (BF) based on biochar and halotolerant strain of growth-promoting rhizobacteria Pseudomonas sp. STF14 on the growth and some physiological and biochemical characteristics of salad mustard (Brassica juncea (L.) Czern, variety “Chastushka”) under salt stress caused by sodium chloride was assessed. Mustard plants were grown in pot-scale experiment for 21 days under natural conditions. The experiment included 4 treatments: control peat soil (PS); PS + BF (2.5%, v/v); PS + NaCl (80 mM); PS + BF (2.5%, v/v) + NaCl (80 mM). From the 7th day after planting the plants were watered with a salt solution twice a week. Adding BF increased the length and fresh biomass of mustard shoots compared to the control (by 23% on average), while NaCl treatment inhibited their growth. BF added separately or together with salt increased photosynthetic pigments. Separate application of BF and NaCl led to the malondialdehyde in mustard leaves increasing by 1.4 and 1.9 times, respectively compared to the control. However, when combined, malondialdehyde decreased by 1.6 times. Watering mustard plants with a saline solution increased the content of free proline by almost 5 times and Na+ by almost 7 times, while BF + NaCl significantly reduced their amount. Thus, the use of BF under salt stress conditions contributed to the improvement of mustard growth and increased its resistance to sodium chloride.