Atmospheric Pressure Dielectric Barrier Discharge Plasma Treatment of Alternaria and Fusarium Species: Impact on Fungal Physiology, Antifungal Sensitivity, and Biofilm Formation.

This study investigated the effects of repeated dielectric barrier discharge (DBD) plasma applications on the morphological and physiological characteristics of pathogenic Alternaria and Fusarium species. Fungi, including both culture collection strains and environmental isolates, were exposed to sublethal doses of DBD plasma. The results demonstrated that the plasma exposure time required to achieve 90% cell mortality varied significantly among microorganisms, ranging from 2 min and 39 s for Fusarium culmorum DSM 1094 to 5 min and 19 s for Alternaria alternata DSM 62010. Tolerance to oxidative stress, assessed by determining the minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of hydrogen peroxide, generally decreased following repeated plasma exposure. Notably, F. tricinctum Ft11S-23 exhibited increased resistance to hydrogen peroxide, with MIC values doubling after fifteen plasma treatments. The MFC also increased significantly, rising from 25.5 mM to 102.0 mM. Furthermore, repeated DBD plasma applications resulted in reduced tolerance of fungi to at least one of the tested fungicides; however, exceptions were observed, including increased tolerance of F. culmorum to specific fungicides. The capacity for biofilm formation was modulated by plasma treatment, with some species exhibiting reduced biofilm formation while others demonstrated increased capacity, depending on the specific pathogen and frequency of plasma exposure.