Biotic interactions modulating stress tolerance in Lablab purpureus

Climate change is increasing the incidence of abiotic stresses such as salinity and drought, which threaten both biodiversity and crop production, leading to economic losses and undermining food security. In this context, promoting sustainable agriculture requires not only the evaluation of stress-tolerant crops but also the identification of beneficial microorganisms capable of enhancing resilience, soil health, and productivity while reducing reliance on agrochemicals.

In this study, we evaluated whether nodule-associated bacteria, isolated from two Mediterranean ecosystems, modulate the response of Lablab purpureus—an underutilised legume with high nutraceutical potential—to salinity and drought. Three salt-tolerant strains (CJND1, LN1RA and LN3BA) were selected, and phenological parameters, biomass and root architecture, photosynthetic pigments, osmolytes, ionic content (Na⁺, Cl⁻, K⁺, Ca²⁺), oxidative stress markers, antioxidant compounds, and antioxidant enzyme activies were assessed.

The inoculated strains exhibited distinct effects. CJND1 and LN3BA promoted root elongation, with LN3BA additionally increasing root surface area and enhancing K⁺ accumulation in leaves. LN1RA increased the chlorophyll a/b ratio and improved nodulation under drought conditions. Overall, bacterial inoculation positively influenced root traits. Salinity reduced biomass, increased proline content, and promoted Na⁺ and Ca²⁺ accumulation in roots while restricting Na⁺ translocation to the shoots. Moreover, salinity tended to increase catalase and superoxide dismutase activities, whereas drought significantly induced glutathione reductase activity and also slightly increased superoxide dismutase activity.

In conclusion, local microbiota, particularly nodule-associated bacteria tolerant to salinity and drought, may represent a valuable tool for the introduction of new agronomic crops such as L. purpureus. Their application could contribute to more sustainable production systems and help safeguard food security in regions such as the Mediterranean, where climate-driven threats are expected to reduce crop yields and water availability.