Inoculation of tomato plants with selected PGPR represents a feasible alternative to chemical fertilization under salt stress

Plant growth‐promoting rhizobacteria (PGPR) are soil bacteria that colonize the rhizosphere of plants, enhance plant growth, and may alleviate environmental stress, thus constituting a powerful tool in sustainable agriculture. Here, we compared the capacity of chemical fertilization to selected PGPR strains to promote growth and alleviate salinity stress in tomato plants (Solanum lycopersicum L.). A pot experiment was designed with two main factors: fertilization (chemical fertilization, bacterial inoculation with seven PGPR, or a non‐fertilized non‐inoculated control) and salt stress (0 or 100 mM NaCl). In the absence of stress, a clear promotion of growth, a positive effect on plant physiology (elevated Fv/Fm), and enhanced N, P, and K concentrations were observed in inoculated plants compared to non‐fertilized controls. Salinity negatively affected most variables analyzed, but inoculation with certain strains reduced some of the negative effects on growth parameters and plant physiology (water loss and K+ depletion) in a moderate but significant manner. Chemical fertilization clearly exceeded the positive effects of inoculation under non‐stressed conditions, but conversely, biofertilization with some strains outperformed chemical fertilization under salt stress. The results point at inoculation with selected PGPR as a viable economical and environment‐friendly alternative to chemical fertilization in salinity‐affected soils.