Plant Growth‐Promoting Rhizobacteria Isolated From Natural Habitats Promote the Growth of <i>Elymus sibiricus</i> and Enhance Its Resistance to Abiotic Stress

<i>Elymus sibiricus</i> L., a perennial tufted herbaceous species native to the Qinghai-Tibet Plateau, serves as a crucial forage resource and plays a vital role in ecological restoration of degraded vegetation. To discover beneficial microorganisms that promote its growth and enhance its stress resistance, this study isolated two novel Plant Growth-Promoting Rhizobacteria (PGPR) strains, <i>Bacillus mycoides</i> GN-1 and <i>Bacillus</i> sp. MQ-5 from rhizospheric soils of wild <i>E.</i> <i>sibiricus</i> populations on the Qinghai-Tibet Plateau. Both strains demonstrated plant growth-promoting traits, including indole-3-acetic acid (IAA) synthesis and siderophore production. In pot experiments, MQ-5 treatment increased aboveground fresh biomass by 25.90% (<i>p</i> < 0.05), increased root biomass by 270.51% (<i>p</i> < 0.001), while GN-1 treatment increased 19.29% (<i>p</i> < 0.05) and 54.38% (<i>p</i> < 0.001), respectively, compared to the control. Furthermore, MQ-5 alleviated salinity and drought stress in <i>E. sibiricus</i>, highlighting its potential for improving forage productivity and resilience in fragile high-altitude ecosystems.