Prunus persica (L.) Batsch root enriched Pseudomonas for enhanced saline-alkali tolerance by inducing fatty acid and flavonoid biosynthesis

Peach (Prunus persica (L.) Batsch) is one of the most widely cultivated economic fruit crops worldwide. However, saline-alkali stress poses substantial challenges to its cultivation and production. This study investigated the synergistic response of peach roots and their rhizosphere microbiota to saline-alkali stress. We examined alterations in the rhizosphere bacterial community and its functional characteristics under such stress using 16S rRNA and metagenomic sequencing. The results indicated a significant enrichment of the genus Pseudomonas in the rhizosphere, accompanied by enhanced functional potential related to cell motility, biofilm formation, and signal transduction. Nine Pseudomonas strains were isolated from the stressed rhizosphere, all of which exhibited plant growth-promoting (PGP) traits in vitro, among which strains R8 showed the most comprehensive PGP profile and most significantly enhanced plant growth in pot experiments. Physiological and transcriptomic analyses demonstrated that R8 inoculation upregulates key genes involved in fatty acid (e.g., FAD, KCS, PAS) and flavonoid biosynthesis (e.g., CHS, CHI, F3H, FLS). This transcriptional reprogramming enhanced membrane stability (increased proline content) and antioxidant capacity (higher flavonoid levels), leading to systemic improvement in saline-alkali tolerance. This study reveals the adaptive strategy of peach to saline-alkali stress mediated by rhizobacteria and highlights the potential of R8 as a microbial inoculant for sustainable cultivation.