Modulation of Physiological Responses and Salinity Tolerance in Rapeseed by Zhihengliuella halotolerans Isolated from the Rhizosphere of Alhagi persarum

Salinity represents a major abiotic constraint limiting crop productivity, making the application of plant growth-promoting rhizobacteria (PGPR) a viable mitigation strategy. In this study, ten halotolerant bacterial isolates were obtained from the rhizosphere of Alhagi persarum. Isolate B1 was selected for analysis based on its superior growth capacity and PGP traits, including indole-3-acetic acid production, siderophore secretion, and ACC deaminase activity. Molecular identification confirmed it as Zhihengliuella halotolerans (99.3% similarity). We conducted a greenhouse experiment on rapeseed (Brassica napus L.) using a factorial design with four salinity levels (0–12 dS m−1). Results indicated that bacterial inoculation significantly mitigated salt-induced impairment of chlorophyll fluorescence parameters. While increasing salinity levels significantly reduced PSII photochemical performance (Fv/Fm, ΦPSII, ETR) and increased energy dissipation (NPQ, ΦNO), inoculation with Z. halotolerans B1 effectively countered these negative impacts, particularly at 6 and 12 dS m−1. Furthermore, bacterial inoculation significantly reduced electrolyte leakage while enhancing the membrane stability index and relative water content. Overall, these findings demonstrate that Z. halotolerans B1 improves the physiological resilience of B. napus under salinity stress by maintaining photosynthetic efficiency, cellular water status, and membrane integrity, offering a promising tool for sustainable crop management under changing environmental conditions.