Harnessing phyllosphere and rhizobium bacteria for salt stress alleviation in common bean (Phaseolus vulgaris)

Salinity is a major constraint to common bean (Phaseolus vulgaris) productivity, yet sustainable mitigation strategies remain limited. Here, we evaluated the interactive effects of salinity stress (0–8 dS m− 1), and plant growth-promoting bacteria inoculations, including Phyllosphere strains (P1 and P2), and Rhizobium (RB), and their combinations (P1 + RB, P2 + RB) on two common bean cultivars (Almas and Pak). Salinity significantly reduced plant height, chlorophyll pigments (Chl a and Chl b), chlorophyll fluorescence (Fv/Fm) and biomass, while elevating oxidative stress markers [malondialdehyde (MDA), hydrogen peroxide (H2O2)] and antioxidant enzyme activity (SOD, CAT). Bacterial treatments, particularly P1 + RB treatment alleviated salinity-induced damage by reducing oxidative stress (up to 68.4%), enhancing ion homeostasis (lower Na⁺, higher K⁺ and Ca²⁺), and maintaining photosynthetic efficiency (Fv/Fm). Almas exhibited greater tolerance than Pak, with lower MDA levels (21.7–25% reduction) and higher phenolic accumulation under stress. Together, these findings highlight the synergistic role of bacterial inoculants and cultivar selection in enhancing salinity tolerance, offering a promising strategy for improving legume resilience and productivity in saline agroecosystems.