Rhizobia strains alleviate salinity in faba beans (Vicia Faba) to valorize marginal sols

Soil salinity remains the most significant limiting factor for the growth of Vicia faba L (faba bean) in Tunisia. Plant growth-promoting rhizobacteria (PGPR) has emerged as a novel way of minimizing the harmful effects of salt stress and improving nutrient accessibility. The aim of this investigation is to study the protective effects of two newly isolated PGPR (rhizobia strains S1 and S2) over 150 mm NaCl salinity stress. Physiological & biochemical parameters along with antioxidant enzymes activities in faba bean culture were measured. The Results showed that salt stress significantly increased nodule biomass in plants inoculated by S1 as compared to S2. Salinity augmented the level of nitrogen in root and shoot in case of S1, while no change was observed with S2 inoculation. Similarly, higher level of potassium and sodium was observed in plants inoculated with S1 compared to S2. Electrolyte leakage (EL) showed an increase of 80% in leaves of plant inoculated with S2 150 mM NaCl against 10.71 % in leaves of plant inoculated with S1 after 10 days of inoculation. After 30 days of inoculation under salinity faba bean-S1 showed a higher value of PPO (8.86 µmol g-1FM) and without salt, the PPO activity was 2 µmol g-1FM. After 40 to 50 days of inoculation, plants inoculated by S1 and S2 showed higher values of phenol content under salinity. The results indicated that salinity significantly increasesd proline accumulation in the leaves and root of faba bean inoculated with S1. However, chlorophylls level was not affected. This study indicates that the S1 rhizobia strain is a prospective inoculant candidate which is essential for promoting growth and production, and thereby reducing the effect of salinity on faba bean plant.