Plasma mediated disinfection of rice seeds in water and air

The efficacy of seed disinfection utilizing atmospheric pressure non-thermal plasma is still a subject of intensive research. Previously, we found that rice seeds infected by Fusarium fujikuroi (fungus causing bakanae disease) could be disinfected via underwater arc discharge plasma. In this study, we further investigated the mechanism of disinfection and the effect on disease severity. In addition, we evaluated disinfection of rice seeds in air by surface DBD plasma. Disease severity was significantly reduced in seedlings germinated from rice seeds treated with underwater arc plasma, compared to non-treated seeds (44%-62% plasma treated compared to 92% non-treated). A shockwave of 11 atm pressure was generated during arc discharge, which likely caused fungal detachment from the seed surface. Moreover, reactive oxygen species such as atomic oxygen (O) was emitted from the underwater arc discharge plasma and could have contributed to the degeneration of the chemical composition on the seed surface and the inactivation of the fungal spores. Rice seeds treated with surface DBD plasma in the presence of H2O2 at a lower pressure (0.6 atm) for 30 min showed the highest seed disinfection efficiency (about 93% seed disinfection) and a significant reduction in disease severity in the germinated seedlings (23% plasma-treated compared to 100% non-treated). Taken together, our results suggested that underwater arc discharge and surface DBD plasma could be usefully applied to develop control strategies for seed-borne fungal diseases via seed decontamination during dry storage or water imbibition before sowing.