New chitosan formulation prevents grapevine powdery mildew infection and improves polyphenol content and free radical scavenging activity of grape and wine.

Background and Aims: Chitosan, a chitin deacetylated derivative, is a biopolymer able to elicit the plant defence machinery against a variety of pathogens. In crop protection, it is successfully employed for its low toxicity, mainly against virus diseases. In this study, the efficacy of a new chitosan formulation (Kendal Cops® (Kc)) was evaluated in grapevine against powdery mildew infection. Total polyphenol (TP) content and antiradical power of different grape tissues and of experimental wines produced from treated grapes were also assessed. Methods and Results: Field treatments with different Kc dilutions or with Kc alternated or mixed with fungicides, or with fungicides alone (penconazole and methyldinocap) were carried out in an experimental vineyard of the cv. Montepulciano d’Abruzzo. Kc was effective in controlling powdery mildew, particularly at the concentration of 0.1%, even under high disease pressure conditions. In this case, disease severity was 2.39% in treated grapes, compared with 87.5 and 0.92% in untreated and conventional fungicide-treated grapevines, respectively. TP content, measured by Folin–Ciocalteau colorimetric assay, was significantly higher in all Kc-treated grape tissues, compared with both untreated controls and fungicide-treated grapes. A similar trend was reported with regard to the antioxidant activity, assessed by 2,2-diphenyl-1-pycryl hydrazyl free radical scavenging test. Analysis of wines showed that both TPs and antiradical power were significantly higher in wines made from Kc-treated grapes compared with fungicide-treated ones. Conclusions: Kc not only protected grapevine from powdery mildew but also improved TP content and antioxidant activity in both grapes and wine. Significance of the Study: The possibility of using plant defence inducers in crop protection deserves particular attention because of their low environmental impact and of their ability to improve some quality traits of plant foodstuffs. Furthermore, in contrast to fungicides, they hardly select resistant pathogen strains and do not incur fitness costs for the plant.