Impact of Ozonated Water on the Fungal Colonies, Diversity and Fruit Quality of Grapevine in Northern Europe

Due to the frequent use of fungicides in viticulture, resistant plant pathogens have emerged, necessitating environmentally friendly alternatives. This research aimed to determine the effect of ozonated water (OW) spraying on fungal colonies present on grapevine leaves and berries, as well as on the biochemical composition of the berries. ‘Regent’ grapevines were grown in a high plastic tunnel and sprayed with OW from post-flowering to harvest. The fungal population on the phyllosphere of grapevine leaves and berries was evaluated using the serial dilution plating method. The taxonomic composition of the predominant fungal colonies was characterized using internal transcribed spacer amplicon sequencing. OW treatment significantly decreased fungal colonies on grapes but had no significant effect on grapevine leaves. The fungal colonies were dominated by Botrytis cinerea, Penicillium brevicompactum, and Fusarium sp. OW treatment significantly reduced the total sugar content in grapes (from 160 to 154 g L−1) and increased the total acid content (from 7.2 to 8.6 g L−1). The fruit polyphenol content increased from 431 to 508 mg 100 g−1, and antioxidant activity was significantly enhanced. It can be concluded that OW treatment is effective in reducing fungal colony forming units on grapes in vineyards. OW treatment affected the sugar, acid, and polyphenol content in grapes, but not to a degree that would present specific challenges for winemakers.