Highlighting the plant responses against multi-stresses: Focus on heat induced grape berries tolerance to Botrytis
Résumé
Vineyards are facing an increase in heat waves due to climate change which can interfere with wine quality and production. In addition, common practices such as leaf thinning expose bunches to higher temperatures, particularly during fruit ripening. These temperature rises modify berry metabolism – i.e. sugar boost in detriment to organoleptic compounds – and potentially their response to diseases, such as gray mold caused by Botrytis cinerea. This fungus infects post-veraison fruit during the summer, and its uncontrolled spreading can severely reduce yield. Our research on fruiting cuttings endeavors to elucidate the intricate interplay between heat stress (HS, 6 days at + 10°C: 25°C vs. 35°C) and tolerance to subsequent Botrytis infection. In order to accurately reproduce vineyard microclimate, HS was applied only at the bunches levels of two prominent varieties, the cabernet-sauvignon and merlot, with contrasting tolerances to B. cinerea. In vitro test on detached berries inoculated 22 days post-HS revealed an improvement in tolerance against B. cinerea only for cabernet sauvignon bunches stressed at herbaceous stage, underscoring sensitivity of stress responses depending on both genetic background and exposure timing. We also investigated the accumulation of chemical and physical barriers in the fruits that with a focus on cuticle – i.e. waxes and cutin – and antimicrobials tannins. The heat-induced tolerance found in our study seems to be without any trade-off for the maturity or yield.