Combined Effects of Seed-Inoculated PGPR and Foliar-Applied Pistachio Hull Wood Vinegar on Salinity Stress Alleviation in Broad Bean (Vicia faba L.)

One of the main abiotic factors that restricts plant growth is salinity, which has a negative impact on a variety of physiological processes. One environmentally friendly method used to lessen the detrimental effects of salt stressors on plants is the application of native stress-tolerant plant growth-promoting rhizobacteria (PGPR) with combined foliar application of wood vinegar (WV). This study aims to evaluate the effectiveness of seed inoculation with the plant growth-promoting rhizobacterium (PGPR) Paenibacillus xylanilyticus strain KF63C, in combination with the foliar application of wood vinegar (WV) derived from regional Siirt pistachio fruit hull biomass, in mitigating the adverse effects of salinity stress (150 mM NaCl) in broad bean (Vicia faba L. cv. Salkım). A 30-day pot experiment was conducted under controlled growth chamber conditions to investigate the effects of two salinity levels (0 and 150 mM NaCl) in combination with six protective treatments: control, PGPR, 0.50% WV, 1.00% WV, PGPR + 0.50% WV, and PGPR + 1.00% WV. The results revealed that high salinity stress (150 mM NaCl) significantly restricted vegetative growth, degraded photosynthetic pigments, and “altered ionic balance, particularly K+ and Na+ accumulation” while increased electrolyte leakage (EL) and malondialdehyde (MDA) accumulation, indicating enhanced membrane damage and lipid peroxidation. Although PGPR inoculation alone improved shoot elongation, its effects on the other physiological traits were variable. Among the tested treatments, PGPR + 0.50% WV showed the strongest numerical response. This combined treatment distinctly minimized oxidative and membrane damage (yielding the lowest EL and MDA levels), maintained cellular ion balance (maintained ionic balance, as indicated by higher K+ accumulation and K+/Na+ ratios under salinity), and helped to maintain chlorophyll and carotenoid concentrations. In contrast, 1.00% WV showed adverse effects on several growth and physiological traits, indicating the importance of dose optimization. These findings suggest that the combined application of PGPR and 0.50% pistachio hull-derived WV may represent a promising sustainable approach for mitigating salinity-induced damage in faba bean.