Inoculation of Pseudomonas fluorescens increases of salt alkali resistance for edible dock and its potential for nitrogen fertilizer substitution

Highly saline-alkaline soil environments inhibit crop growth and development and are a key bottleneck when attempting to improve and utilize saline-alkaline land. To address the critical challenge of saline-alkaline soil remediation, this study investigated the efficacy of recombinant nitrogen-fixing (nif) bacteria (Pseudomonas fluorescens CHA0-nif) in enhancing seed germination of an edible dock (Rumex spp.) under saline-alkaline stress and their potential to replace chemical nitrogen fertilizers. Indoor germination assays and pot experiments with graded nitrogen reduction (0%, 10%, 20%, 30%) were conducted. Key findings include: 1) Under moderate saline stress, CHA0-nif significantly improved germination rates germination rates by 13.26%~16.40% and shoot elongation by 8.89%~34.56%, outperforming the wild-type strain (WT). No growth promotion was observed under high stress. 2) Soil nitrate nitrogen content increased by 27.25%~54.59% with CHA0-nif inoculation, with sustained enhancement under 10%~20% nitrogen reduction. 3) CHA0-nif increased root biomass by 48.02% and total plant nitrogen accumulation by 41.37%. Stable aboveground biomass and nitrogen uptake were maintained at 20% nitrogen reduction, whereas 30% reduction caused significant declines in all parameters. These results demonstrate that CHA0-nif enhances forage grass adaptation to moderate saline-alkaline stress and enables 20% nitrogen fertilizer replacement, offering a novel microbial strategy for sustainable saline soil rehabilitation.