Boosting the Brassica napus L. tolerance to salinity by the halotolerant strain Pseudomonas stutzeri ISE12

Abstract Soil salinisation is one of the major pervasive environmental hazards and abiotic stress factors limiting plant productivity worldwide. Since most of the known crops are susceptible to high salinity, there is great interest in improving technologies in agriculture and making major crop species more robust and productive under saline conditions. In our work, we hypothesized that halotolerant plant growth promoting endophytic bacteria may have a beneficial effect on the growth and development of Brassica napus L. cultivated under salt stress conditions. The main aim of our study was to evaluate the role of the Pseudomonas stutzeri ISE12 strain, isolated from the halophyte Salicornia europaea , in mitigating salt stress in Brassica napus L. Verification of the influence of P. stutzeri on B. napus was based on the wide range of plant parameters responsible for abiotic and biotic stress factors: growth and biochemical parameters, the level of RSH gene expression, and changes in the chemical composition and physical properties of cell walls. In accordance with our assumption, salinity decreased plant growth and increased levels of proline, total glutathione and lipid peroxidation in plants. Inoculation of plants with the halotolerant P. stutzeri ISE12 increased the plant growth in both types of substrate (non-saline and saline) and decreased the accumulation of non-enzymatic antioxidants. The RSH1 and RSH3 gene expression in B. napus organs depended on the level of salinity and bacterial inoculation, while we have not observed effect of these biotic and abiotic factors in the case of CRSH and RSH2 genes. Moreover, increased levels and changes in the distribution of homogalacturonans (HGs) with varying de-esterification patterns were observed in cell walls in response to saline stress. In conclusion, inoculation of B. napus with the halotolerant strain P. stutzeri ISE12 alleviates the salt stress experienced by host plants by activating their antioxidant defence system and triggering the rearrangement of cell walls, which, consequently, promotes plant growth.