Effects of non-thermal plasmas on seed-borne Diaporthe/Phomopsis complex and germination parameters of soybean seeds

Diaporthe/Phomopsis (D/P) is a complex of seed-borne fungi that severely affects soybean (Glycine max (L.) Merrill), one of the most important crops worldwide. Non-thermal plasma treatment is a fast, economic and ecological friendly technology that can destroy seed-borne fungi and improve seed quality. Soybean seeds were exposed for 1, 2 and 3 min to a quasi-stationary (50 Hz) dielectric barrier discharge plasma operating at atmospheric pressure air. Different carrying gases (O2 and N2) and barrier-insulating materials were used. In this work we focused on the ability of plasma to control D/P in soybean seeds and to enhance seed quality. To support these results, different antioxidant enzymes (catalase, superoxide dismutase and guaiacol peroxidase), lipid peroxidation and phytohormones (ABA and AIA) content in seeds were evaluated. The results demonstrated reductions of 29% in catalase activity and increments of 30% in glutathione content after plasma treatment, reversing the oxidative damage caused by D/P fungi. This eco-friendly technology improved soybean seed quality and, for the first time, its efficiency in controlling soybean seed-borne pathogen fungi that colonize the inside of seeds was demonstrated.