HYBRID GRAPEVINE CV BACO BLANC, BETWEEN TRADITION AND MODERNISM: FOCUS ON ENDOGENOUS EUGENOL AS RESISTANCE FACTOR TO BOTRYTIS CINEREA
The well-known antifungal and antibiotic molecule, eugenol, is widely spread in various plants inclu-ding clove, basil and bay. It is also abundant in the hybrid grapevine cultivar (cv) Baco blanc (Vitis vinifera x Vitis riparia x Vitis labrusca), created by François Baco (19th century) in the Armagnac region. This study confirmed this cv as highly resistant to Botrytis cinerea by comparing fruit rot incidence and severity with two Vitis vinifera cultivars: Folle Blanche and Ugni Blanc. We have demonstrated the efficiency of eugenol in vitro, by further investigating the effect of small concentrations of eugenol, 3 to 4 ppm (corresponding to IC10), on B. cinerea. By comparing the two major modes of action (direct or volatile antibiosis), the vapour inhibiting effect of eugenol was more powerful. In the skin of Baco blanc berry, the total eugenol concentration reached a maximum at veraison, i.e. 1118 to 1478 μg/kg. Leaf removal in the bunch zone induced a significant increase of 32 % in eugenol at veraison, which was also associated with a significant decrease in B. cinerea infection in the vineyard. Eugenol, as a natural endogenous molecule of Baco blanc, is therefore an inducible compound. Very interestingly, in terms of fruit ontogenic resistance, a significant negative correlation was established between the technological maturity of berries and the total eugenol content in the berry skin. This correlation was observed on 3 plots and confirmed over several years (2021 and 2022): it therefore appears to be intrinsic to the biology of cv Baco blanc. Moreover, the temporal study of two forms of eugenol tends to hypothesise the effectiveness against B. cinerea of precursor forms of eugenol. Such bound forms are structures which are currently being researched in our laboratory. For all these reasons, eugenol appears to be a biochemical marker of ontogenic resistance in Baco blanc and presumably an important resistance factor in this old cv of renewed interest.
Issue: OENO Macrowine 2023
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ontogeny, inducibility, resistant hybrid vine, phenylpropanoids