Essential oil-based emulsions reduce bacterial canker on kiwifruit plants acting as antimicrobial and antivirulence agents against Pseudomonas syringae pv. actinidiae

Pseudomonas syringae pv. actinidiae (Psa) poses a significant threat to global kiwifruit production, with current control measures proving insufficient and fostering resistance development. Essential oils (EOs) offer a promising alternative due to their multifaceted antimicrobial and antivirulence mechanisms. This study evaluated the antimicrobial activity of various EOs—cinnamon bark (CIN), oregano (ORE), clove bud (CLO), and thyme (THY)—against Psa, in terms of growth and virulence traits. CIN exhibited the highest antimicrobial activity, followed by ORE and CLO EOs, while THY EO was less effective. Encapsulation of EOs into organic polymer-based emulsions enhanced their antimicrobial efficacy by improving bioavailability and stability while reducing the required dosage. Notably, CIN and ORE EO emulsions effectively reduced disease symptoms in kiwifruit under both in vitro and in vivo conditions. Mechanistically, these EOs demonstrated dual activity: direct antimicrobial effects likely via membrane alteration and indirect antivirulence effects, including the inhibition of biofilm production and type III secretion system induction. Field trials further confirmed the potential of EO-based formulations to reduce disease incidence and severity over a growing season. This study underscores the potential of EO emulsions as sustainable, cost-effective plant protection agents, aligning with the goals of environmentally friendly crop management strategies.