The Pseudomonas fluorescens Complex: Molecular Mechanisms of Plant-Beneficial Traits and Biotechnological Applications in Crop Production

The Pseudomonas fluorescens complex represents one of the most ecologically versatile and functionally diverse groups of plant-associated rhizobacteria, offering substantial promise for sustainable crop production. Members of this bacterial group exhibit a broad array of plant-beneficial effects, including growth promotion, biocontrol against phytopathogens and insect herbivores, and mitigation of abiotic stresses such as drought, salinity, and heavy metal toxicity. Despite their potential, the application of P. fluorescens complex strains in commercial inoculants remains limited, and their field performance is variable across different agricultural environments. To advance the development of effective microbial products, a clear understanding of the mechanisms underlying their plant growth promotion activities and stress mitigation is essential. In this review, we synthesize current knowledge on the taxonomy, ecological roles, and molecular mechanisms of beneficial activity within the P. fluorescens complex, and highlight key traits contributing to plant growth promotion, biocontrol, and abiotic stress tolerance, with discussion of challenges and future directions for their application in sustainable agriculture.