The Role of Plant Growth-Promoting Rhizobacteria in Improving Pea (Pisum sativum) Cultivars Under Salt Conditions

Context: Salinity is one of the main challenges facing agricultural production systems in arid and semi-arid regions, where it is accountable for a significant loss in crop productivity. In Tunisia, salt-affected soils are covering 1.5 Mha of the total cultivated area and new lands are affected through saltwater intrusion. They are generating soil–plant water system disorders that decrease plant water and essential nutrients availability and reduce productivity. Plant Growth-promoting Rhizobacteria (PGPR) is an innovative approach that has demonstrated its potential utility in improving plants growth under abiotic stresses and providing resilience in saline ecosystems. Methods: The present study aims to screen high tolerant bacteria and evaluate their influence on pea plants growth and biochemical status under salt conditions. For that, bacterial isolates from pea nodules were inoculated to three salt-sensitive pea varieties (Douce de Provence DP, Rahma RH, and Nejma NJ) in a hydroponic square box trial and irrigated with salty water. Plants were evaluated for growth, chlorophyll content, and stress markers accumulation. Results: The obtained results showed that among 15 bacterial isolates, the strains Sb3 and S24 were able to tolerate the highest NaCl concentration (83.5 dS/cm). The three-way ANOVA analysis of pea plants measured parameters showed that salinity stress induced a significant reduce in shoot and coleoptile length and fresh weight that is dependent on variety type. Although, coleoptile growth was simultaneously affected by salt, variety, and inoculated strain. In addition, under salt stress, the chlorophyll content of leaves is significantly decreased in all varieties compared to uninoculated plants, especially in DP variety. This alteration was remediated following inoculation of DP with Sb3 and NJ and RH with S24. Similarly, the survey of oxidative stress in pea plants showed that hydrogen peroxide (H2O2) and Malondialdehyde (MDA) content of salt-stressed plants is significantly deceased in DP following Sb3 inoculation and in NJ and RH following S24 inoculation. Interpretation: Our study suggests that pea plants exposed to salt stress have modulated several response mechanisms in favor of their defense causing harmful changes in physiologic and biochemical mechanisms. However, plants treated with PGPR has a powerful antioxidant defense system, which conferred salinity resistance. Conclusion: These findings suggest that halotolerant rhizobacteria could enhance plant growth and productivity by mitigating deleterious salt stress effects, while providing an ecological approach for managing saline conditions in agricultural production systems.