A Non-thermal Plasma Seed Treatment Method for Management of a Seedborne Fungal Pathogen on Rice Seed

Seeds contaminated with pathogens are the primary inoculum for plant diseases in many food crops. Conventional treatments for seedborne diseases use hot water, chlorine or fungicide applications. A novel seed treatment method based on non-thermal plasma generated by an air dielectric barrier discharge (DBD) device was evaluated in this study as an alternative to these conventional treatments. The non-thermal plasma at atmospheric pressure and room temperature consisted of partially-ionized gases that are chemically reactive. The antimicrobial activity of non-thermal plasma was evaluated against an important seedborne pathogen, Gibberella fujikuroi, that causes bakanae disease in rice. Non-thermal plasma treatments effectively inhibited the growth of G. fujikuroi on nutrient growth medium and reduced the number of fungal colony forming units (CFU) on the rice seed surface by > 92% after 120 s exposure. Effective exposure times to 50% (ET50) and 90% (ET 90) control of G. fujikuroi CFU on the seed surface were 9 and 76 s, respectively. Ten minutes of non-thermal plasma treatment on seeds infested with G. fujikuroi significantly reduced disease development. No adverse effects were detected on the seedling emergence and height when non-infested seeds were treated with non-thermal plasma for up to 20 min. The treated seeds germinated and grew similarly compared with non-treated non-infested seeds. This study indicates that non-thermal plasma had antifungal activity and showed potential as an effective disinfection technique to reduce the contamination of seedborne fungal pathogens from seed surfaces without compromising seed health.