Sonoplasma Technology for Water Treatment Against Phytopathogenic Fungi: Responses of Melanized and Hyaline Species

Sonoplasma treatment (SPT), which combines hydrodynamic cavitation with low-temperature plasma discharge in water, has been proposed as an advanced oxidation process for reducing biological contamination. By generating physical stressors and reactive oxygen species, including hydrogen peroxide (HP), SPT may inactivate microorganisms, but its effects on stress-resistant filamentous fungi remain insufficiently characterized. We examined two phytopathogenic fungi with contrasting pigmentation: melanized Alternaria alternata and hyaline Fusarium solani. Spore suspensions were exposed to direct and indirect SPT at 30 kHz, and viability, biomass accumulation, conidial production, allelopathic activity, and pigmentation-associated spectral responses were assessed immediately after treatment and after storage. Fungus F. solani showed greater susceptibility, with reduced colony-forming capacity and suppressed biomass production, although surviving propagules showed increased sporulation. In contrast, A. alternata maintained viable growth under the tested conditions and showed stimulation of growth-related and reproductive endpoints, together with darker colony pigmentation. These responses are consistent with pigmentation-associated tolerance to SPT-induced physical and oxidative stress, but do not establish melanin as the sole causal mechanism. SPT efficacy against filamentous fungi is therefore species-dependent and may be limited when resistant melanized taxa are present.