Abstract
A two-year study was conducted in an organic vineyard to evaluate the phytochemical content and antioxidant capacity of grapes treated with low-rate copper quantities for downy mildew control, in comparison with an untreated test and to a standard fungicide. The metabolic profile and antioxidant capacity were analyzed in relationship with the results of downy mildew incidence and severity. The maturity level of grapes appeared an important parameter in determining the potential risk for the spread of fungal disease, as suggested by the results of PCA analysis that showed a positive relationship between the tartaric acid content with both incidence and severity of downy mildew disease. Polyphenols and thiols amounts resulted higher in grape berries with lower disease levels. The thiols were highly correlated with the antioxidant capacity, indicating an important role of these metabolites in determining the antioxidant potential of grape berries. Moreover, the fact that in PCA both the antioxidant indexes and thiols were plotted at the opposite of the disease severity and incidence, suggests that an higher antioxidant potential may be responsible for a better capacity of grapes to counteract the disease. Finally, the present findings showed that low-copper formulations were able to control grape downy mildew in the field with a similar effectiveness compared to the standard reference fungicide, without affecting the phytochemical profile and the antioxidant potential of grapes. Low-copper formulations may be thus considered alternative formulates to be used in organic agriculture in order to minimize costs as well as copper accumulation in the soil, so ensuring the most possible grape quality in a sustainable crop management.
- ©2014 by the American Society for Enology and Viticulture
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