Evaluation of a novel chitosan-based defense elicitor for the reduction of fungicide and copper inputs while preserving yield, grape, and wine quality

Abstract

The use of fungicides and copper-based products to control grapevine diseases has raised concerns regarding their environmental impact and potential risks to human health. To reduce reliance on these inputs, new biostimulants and defense inducers have emerged, among which chitosan is one of the most widely studied due to its versatile properties as both an antimicrobial agent and an elicitor of plant defense mechanisms. In this study, we evaluated the efficacy of an innovative chitosan-based product (hereafter ICBP), a complex preparation developed using a patented technology (patent FR3145668), in reducing copper or fungicide inputs for the control of downy mildew (Plasmopara viticola) incidence and severity in vineyards. In addition, we assessed the biostimulant effects of chitosan on grape quality and potential wine quality. The experiment was conducted in a vineyard (Toulouges, 66300 France) between April and August 2025. Twenty plots (~20 m²; 10 plants: Vitis vinifera cv. Chardonnay) were assigned to five experimental groups in a randomized complete block design: (1) untreated control; (2) full recommended dose of copper (BB Protect); (3) half-dose copper (BB Protect) combined with 2 L ha⁻¹ ICBP; (4) full recommended dose of fungicides (Polyram, Redelli, Tebaide); and (5) half-dose fungicides combined with 2 L ha⁻¹ ICBP. In total, eight applications were performed according to standard viticultural practices. Disease severity, as well as grape physiological and biochemical parameters, were measured at harvest. Downy mildew pressure was ensured by four controlled inoculations with Plasmopara viticola to promote uniform disease development across experimental groups. Grape quality parameters included pH, total acidity, malic acid content, amino nitrogen, ammonium, yeast-assimilable nitrogen (YAN), sugar content (°Brix), and potential alcohol. Our study shows that eight applications of ICBP allowed a 50% reduction in copper or fungicide doses while maintaining 100% plant protection, equivalent to that achieved with full-dose treatments. The results indicate that combining ICBP with half of the conventional dose provides the same technical performance as the full treatment, while slightly improving grape balance. Sugar content, potential alcohol, YAN, and amino nitrogen levels remained essentially unchanged, indicating that dose reduction does not compromise ripeness or fermentation security.

References

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