24-Epibrassinolide enhances sweet cherry resistance to bacterial canker by alleviating oxidative damage

• EBR enhances resistance to bacterial canker in sweet cherry. • EBR strengthens antioxidant defense capacity and associated host defense responses. • EBR induces host resistance without direct inhibition of Pseudomonas syringae growth. Sweet cherry ( Prunus avium L.) is a high-value fruit crop whose production is threatened worldwide by bacterial canker, a disease with major economic impacts for which sustainable control strategies are urgently needed. While 24-epibrassinolide (EBR) is recognized as a key regulator of plant immunity, its role and mode of action in woody fruit species, particularly against bacterial pathogens, remain poorly understood. This study investigated the effects and underlying mechanisms of EBR against bacterial canker in two commercially important sweet cherry cultivars, ‘Rainier’ and ‘Sunburst’. Treatment with 0.5 μM EBR significantly reduced disease symptoms and alleviated oxidative stress, as reflected by decreased accumulation of O₂⁻, H₂O₂, and malondialdehyde (MDA), together with enhanced activities of key antioxidant enzymes (SOD, CAT, POD, APX, PPO, and PAL) and upregulation of their corresponding genes ( PavSOD, PavCAT, PavPOD, PavAPX, PavPPO , and PavPAL ). In vitro assays further confirmed that EBR does not directly inhibit Pseudomonas syringae pv. syringae , suggesting that the observed resistance is associated with activation of host defense responses. Collectively, these results suggest that EBR enhances disease resistance in sweet cherry by strengthening host antioxidant defense capacity. These findings support the potential of EBR as an eco-friendly regulator for sustainable management of bacterial canker and related diseases in perennial fruit crops, offering a broadly applicable strategy for fruit tree production under different agroecological conditions.