Plant-Growth-Promoting Rhizobacteria as a Sustainable Strategy for Enhancing Quinoa Resilience to Salt Stress in Arid Regions

Soil salinity and water scarcity are major challenges limiting agricultural productivity in arid and semi-arid regions. Quinoa (a climate-resilient crop) offers potential for sustainable food production under these harsh conditions; however, its growth and yield are often constrained by salt and water stress. This study evaluated the role of plant-growth-promoting rhizobacteria (PGPR) in enhancing Chenopodium quinoa Willd performance under deficit irrigation (DI) with saline water. A greenhouse pot experiment was conducted with four irrigation levels (40%, 60%, 80%, and 100% of the growth water requirement, GWR) and two water qualities (fresh water, EC = 0.8 dS m−1; and saline water, EC = 6.0 dS m−1), each tested with and without PGPR inoculation. The results showed that PGPR application significantly (p < 0.05) improved quinoa tolerance to salinity, leading to higher biomass, yield, and crop water productivity (CWP) under saline irrigation. Yield reductions were most severe at 40% GWR (53.9% and 82.6% under saline and fresh water, respectively), but PGPR inoculation mitigated yield losses, with increases of 83.3% and 130.8% under 40% and 100% GWR saline irrigation, respectively. Notably, PGPR did not show a clear effect with freshwater irrigation. In addition, inoculated plants exhibited improved nutrient uptake and reduced heavy metal accumulation. Overall, PGPR demonstrated strong potential to enhance salinity resilience and water-use efficiency in quinoa. Future studies should extend these findings under field conditions and investigate the long-term impacts of PGPR on sustainable crop production in saline- and water-limited environments.