Plant Growth-Promoting Activity and Whole-Genome Analysis of Pseudomonas marginalis RA62c-B2 Isolated from Vitis amurensis

Bacteria of the genus Pseudomonas act as effective plant growth promoters, realizing their potential through a complex of physiological mechanisms—from phytohormone synthesis to nutrient mobilization and suppression of phytopathogens. These properties position Pseudomonas strains as promising candidates for the development of environmentally friendly biopreparations in sustainable agriculture. The study presents a comprehensive characterization of the Pseudomonas marginalis RA62c-B2 strain isolated from Amur grapevine (Vitis amurensis), combining genome-wide analysis with laboratory and plant-based experimental validation. The genome of P. marginalis RA62c-B2 comprises 6,620,267 bp and encodes 6545 protein-coding sequences. Genomic analysis revealed a suite of functional genes that support plant growth promotion, including those engaged in indole-3-acetic acid (IAA) and cytokinin biosynthesis, organic acid production, nitrogen metabolism, phosphorus and potassium mobilization, iron assimilation, sulfur metabolism, resistance to osmotic and oxidative stress, and bioremediation potential. In conjunction with genomic data, metabolite profiling by HPLC-MS provided functional validation of the strain’s biosynthetic pathways: tryptophan metabolites (indole-3-acetaldehyde and indole-3-carboxaldehyde) were identified, along with two cytokinins (trans-zeatin and N6-isopentenyladenine), detected in the P. marginalis RA62c-B2 culture extract. Furthermore, a single inoculation of rice seeds with P. marginalis RA62c-B2 significantly enhanced the growth parameters of seedlings and 30-day-old plants. These phenotypic effects are consistent with the strain’s genetic profile, reflecting its multifaceted capacity to promote plant growth through multiple complementary mechanisms.