Mitigation of salinity stress via improving growth, chlorophyll contents and antioxidants defense in sunflower with Bacillus pumilis and biochar

Increasing salinity stress is a significant challenge in agriculture, affecting ~ 20% of irrigated areas worldwide. It can induce osmotic stress, oxidative stress, and nutrient imbalance in plants. Using rhizobacterial species and biochar can be an effective method to overcome this issue. Bacillus pumilus is a rhizobacteria that can enhance plant salt tolerance, facilitate nutrient solubilization in saline soils, and generate stress-alleviating metabolites. On the other hand, nitrilotriacetic acid mixed biochar (NAT-BC) can increase crop yields and mitigate salt stress by improving nutrients and water uptake. That's why the present study was carried out to explore the combined effect of NAT-BC and Bacillus pumilus on sunflowers in both non-saline and salinity-stress on sunflowers. Four treatments, i.e., 0NAT-BC, Bacillus pumilus, 0.75NAT-BC, Bacillus pumilus + 0.75NAT-BC, were applied in four replications following a completely randomized design (CRD). Results showed that Bacillus pumilus + 0.75NAT-BC caused significant enhancement in sunflower plant height (103%), stem diameter (45%), head diameter (74%), stomatal conductance (60%), and protein content (11%) rate over control under salinity stress. A significant improvement in sunflower chlorophyll a (19%), chlorophyll b (35%), and total chlorophyll (54%) compared to the control confirm the efficacy of Bacillus pumilus + 0.75NAT-BC under salinity stress. It is concluded that applying treatment Bacillus pumilus + 0.75NAT-BC can alleviate salinity stress in sunflowers via improvement in total chlorophyll contents, which was the most representative attribute in the current study. Growers are recommended to apply Bacillus pumilus + 0.75NAT-BC to achieve better sunflower growth under salinity stress.