Mechanism and control efficacy of plasma-activated water seed treatment against bacterial fruit blotch in melon seedlings.

BACKGROUND Bacterial fruit blotch (BFB) of melons, induced by Acidovorax citrulli, is a severe seed-borne disease. Traditional chemical seed treatments risk environmental pollution and antibiotic resistance. Plasma-activated water (PAW), as an innovative, efficient, eco-friendly and nontoxic method for seed disinfection, demonstrates significant potential for application. However, the efficacy and mechanisms of PAW in seed treatment for controlling BFB in melons remain poorly understood. RESULTS This study investigated the efficacy of PAW produced by underwater jet-array gas-liquid plasma discharge in controlling BFB caused by A. citrulli. Soaking seeds in PAW (generated by a 1-h plasma discharge) for 4 h significantly decreased the disease incidence and severity, with a 97.2% decrease in the disease index compared to the control group. Furthermore, plant growth metrics showed marked improvement, including increases of 5.51% in plant height, 5.04% in stem diameter, 18.10% in leaf area and 27.58% in root length. Scanning electron microscopy, Fourier transform infrared and X-ray photoelectron spectroscopy analyses revealed that reactive oxygen/nitrogen species (RONS) in acidic PAW etched seed coats, suppressed bacterial growth and altered chemical bonds (reducing C─C/C─H while enhancing C─N/C─O), collectively improving seed activity. CONCLUSIONS This study offers an effective and practical strategy for managing BFB in seedlings. PAW seed treatment reduces crop damage from bacterial diseases, enhances seed physiological activity and lowers environmental risks compared with conventional chemical treatments. © 2025 Society of Chemical Industry.