Harnessing the roles of halotolerant rhizobacteria in salt stress modulation in the Rio Grande tomato plant variety

This research aims to identify salt-tolerant rhizobacteria that can be used to improve tomato plant growth under salt stress. In this study, we isolated rhizobacteria from dune flora in the northern mountainous region (34°39′ N, 10°43′ E) around the Mediterranean Sea within the Centre of Biotechnology Sfax, Tunisia. Among 90 bacterial isolates, 24 bacterial strains were promising halotolerant, and an in vivo assessment of their salt tolerance was conducted, ultimately singling out Bacillus tequilensis and Bacillus zanthoxyli, which exhibited exceptional salt tolerance. Their efficacy was evaluated through potted plant experiments, assessing the salt stress markers on the growth of tomato plants under varying salinity stress. The results of the tomato plants inoculated with B. tequilensis and B. zanthoxyli showed a reduction in the levels of hydrogen peroxide (20 and 25%, respectively), malondialdehyde (15 and 23%, respectively), and electrolyte leakage (11.44 and 16.88%, respectively) with an increase in the relative water content of tomato by 40.15% and 24.59%, growth parameters, and the osmolytes concentrations as compared to the salt-stressed tomato plants. Our study revealed that B. tequilensis was more potent in the reduction of salt stress effects on tomato plants. Thus, it may be used as a biofertilizer and as an alternative approach for plant growth and development under high soil salinity conditions. Therefore, an understanding of the underlying mechanisms and biochemical pathways (synthesis of compatible solutes and stress markers reduction) involving B. tequilensis that influence physiological and morphological properties of salt-stressed tomato plants is needed in the future.