Microwave plasma treatment for seed-borne bacterial fruit blotch control and seed germination assessment in watermelon

Bacterial fruit blotch (BFB), caused by the seed-borne pathogen Acidovorax citrulli , poses a serious threat to watermelon ( Citrullus lanatus ) production worldwide. This study evaluates the efficacy of a custom-built microwave plasma system for simultaneous seed disinfection and assessment of germination responses. Watermelon seeds artificially inoculated with A. citrulli were treated with microwave plasma under vacuum at 240 W for 30, 60, and 90 min. Quantitative PCR and colony-forming unit (CFU) analyses revealed significant reductions in pathogen levels across all treatment durations, with up to 98.1% reduction following 90 min of exposure. In vitro seedling growth assays demonstrated that the 30-min treatment group showed a tendency toward greater early seedling elongation, although differences among treatments were not statistically significant. In vivo germination tests confirmed high germination rates (>93.8%) in all plasma-treated groups, with germination performance comparable to or slightly higher than that of the untreated control group. Contact angle measurements showed that plasma exposure improved seed surface wettability, potentially facilitating water uptake. These findings suggest that microwave plasma treatment may reduce seed-borne pathogen load while maintaining stable germination performance under selected treatment conditions. This non-chemical method may provide a sustainable alternative to conventional seed sterilization techniques and demonstrates the feasibility of pilot-scale microwave plasma treatment for controlled batch processing of agricultural seeds.