Mechanisms of Pseudomonas spp. as plant growth promoting rhizobacteria: plant nutrition and biocontrol

Increasing concerns over excessive agrochemical use, the emergence of resistant phytopathogens, and the impacts of climate variability on crop productivity have increased interest in plant growth promoting rhizobacteria (PGPR) as promising biological alternatives for sustainable crop production. Pseudomonas spp. are among the most extensively studied PGPR due to their remarkable metabolic diversity, strong rhizosphere colonization, and multifunctional roles in enhancing plant nutrition, improving stress tolerance, and suppressing plant diseases. These Gram-negative bacteria enhance plant growth through diverse direct and indirect mechanisms, including biological nitrogen fixation or stimulation of nitrogen fixation in co-existing diazotrophs, phosphate solubilization, siderophore-mediated iron acquisition, nutrient and niche competition with pathogens, secretion of antimicrobial metabolites, and activation of induced systemic resistance in plants. Recent advances in omics technologies have improved understanding of the mechanisms underlying Pseudomonas mediated plant nutrition and biocontrol. However, these insights remain fragmented across the literature, limiting a comprehensive understanding of Pseudomonas-plant interactions. This review synthesizes current knowledge on nutrient mobilization, siderophore activity, antimicrobial metabolite production, and induced plant defense responses associated with beneficial Pseudomonas spp. Emphasis is placed on how these mechanisms collectively enhance plant productivity, stress tolerance, and disease resistance, highlighting the potential of Pseudomonas spp. as sustainable biofertilizers and biopesticides.