Alleviation of salt stress in rapeseed (Brassica napus L.) plants by biochar-based rhizobacteria: new insights into the mechanisms regulating nutrient uptake, antioxidant activity, root growth and productivity

Amendment of saline soils with biochar and rhizobacteria is a new technique to diminish the negative impacts of salt stress on plants. Hence, an original pot experiment was conducted in a glass greenhouse at the University of Tabriz to investigate the performance of salt-stressed (0, 6 and 12 dS m−1 NaCl) rapeseed (Brassica napus L.) plants in response to different biochar-related treatments (non-biochar, biochar, biochar-based Pseudomonas putida RS-198, biochar-based Azotobacter chroococcum RS-106 and both bacteria). The biochar-related treatments reduced sodium content, generation of reactive oxygen species, lipid peroxidation and enzymatic antioxidants in plant tissues while enhanced nutrient content, non-enzymatic antioxidants, main and lateral roots lengths and weights, main/lateral root length ratio, specific root length, root diameter, shoot length and weight, leaf area, chlorophyll content and seed and oil yields under saline conditions. The biochar-based Pseudomonas + Azotobacter was the superior treatment for reducing the harmful impacts of salt stress on rapeseed plants, which resulted in 83–109% and 69–115% improvements in seed and oil yields of this crop under moderate and high salinities, respectively. Therefore, inoculation of biochar with both rhizobacteria might be a novel approach for improving salt tolerance and productivity of rapeseed plants.