Disinhibition of grapevine immune responses: An innovative strategy to improve plant defense inducers efficiency

Abstract

Among the approaches aiming to reduce our reliance on usual phytosanitary products, stimulating plant immune responses is a promising strategy. However, the protection induced by plant defense inducers (PDI) remains often insufficient or inconsistent. In previous fundamental studies carried out on tobacco, we demonstrated that type 2 histone deacetylases (HD2), a family of HDACs specific to plants, act as negative regulators of immune response intensity. We identified a natural, non-toxic molecule (thereafter called “disinhibitor”) that inhibits HD2s, thereby lifting their repressive effect. This led us to develop a “disinhibition” strategy, combining the disinhibitor with a PDI to enhance the level of induced protection against diseases. Under controlled conditions, using grapevine and downy mildew/powdery mildew pathosystems, we showed a synergistic effect between the disinhibitor and the PDI used at reduced doses, achieving full protection. This increased efficacy is notably characterized by stronger and longer-lasting activation of defense genes, such as those involved in the stilbene phytoalexin synthesis. As part of the DEREBIO project (ANR Ecophyto Maturation), in collaboration with Cérience and the BC2Grape platform of UMR SAVE in Bordeaux, we tested this disinhibition strategy together with reduced doses of copper. Experiments were carried in experimental plots and with lead winegrowers across diverse soil and climate contexts during the 2024 and 2025 vintages, marked by a severe and moderate downy mildew pressure, respectively. On cv Chardonnay, the combined use of a reduced copper dose (50% below the approved rate), the disinhibitor, and a half-dose of PDI provided a level protection similar to that obtained with the standard copper treatment, without significantly increasing treatment costs. Importantly, we showed that the application of disinhibition strategy does not alter the biochemical characteristics of the berries or the physiology of the plant. This innovative biocontrol strategy, for which an international patent has been filed, holds promise for effective disease management against grapevine fungal pathogens under field conditions.

References

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