Plant-Derived Anti-Virulence Metabolites Targeting Gram-Negative Phytopathogens: Recent Advances and Perspectives

Plant specialized metabolites play important roles in plant–microbe interactions. Beyond direct antimicrobial activity, some can attenuate pathogen virulence without markedly inhibiting microbial growth. Many gram-negative phytopathogenic bacteria cause important crop diseases and possess interconnected virulence systems, providing multiple opportunities for intervention by plant-derived anti-virulence metabolites. In this review, we summarize recent advances in these metabolites against gram-negative phytopathogenic bacteria according to three functional levels: virulence signal decision-making, virulence execution, and pathogenic ecological phenotypes. Particular attention is given to the strength of mechanistic evidence, including target engagement, pathway modulation, and disease-related outcomes. We further interpret these activities in the chemical-ecology context of plant–pathogen interactions and discuss the challenges and prospects of developing plant-derived metabolites as anti-virulence agents.