The role of berry skin traits in fungus-resistant PIWI grapevines

Summary

The Interreg-funded project WiVitis aims to strengthen cross-border collaboration between research institutions and viticultural practice within the Upper Rhine region to promote sustainable viticulture and improve adaptation to climate change. The project focuses on evaluating PIWI grapevine varieties with multiple resistance genes against downy and powdery mildew, with the objective of assessing their resilience under extreme climatic conditions and their susceptibility to fungal pathogens, including Botrytis cinerea. PIWI varieties characterized by high berry firmness are being examined across various sites and environmental conditions. Participating institutions include the Julius Kühn-Institut (Germany), Dienstleistungszentrum Ländlicher Raum Rheinpfalz (Germany), the Research Institute of Organic Agriculture (FiBL-Switzerland), INRAE (France), the State Viticulture Institute Freiburg (WBI) (Germany), and the Swiss Nanoscience Institute (Switzerland). The grape berry skin represents a complex, multifunctional tissue that plays a pivotal role in both plant defense and wine quality determination. Serving as the fruit’s primary protective barrier, it provides defense against fungal pathogens such as Botrytis cinerea (gray mold), mitigates mechanical damage during harvest and processing, and contains numerous compounds critical to the grape’s sensory and chemical characteristics. At FiBL-Switzerland, we are investigating skin traits in fungus-resistant PIWI grape varieties using a combination of penetrometer measurements to determine skin firmness, cryo-scanning electron microscopy (CRYO-SEM) of the grape surface to assess wax morphology, and cross-sectional analysis to measure skin thickness. Additionally, artificial grape inoculations in vitro are performed to evaluate the susceptibility of different PIWI and European grape varieties to Botrytis cinerea infections. The preliminary results indicate differences in both wax morphology and skin thickness among varieties, which may contribute to the varying levels of susceptibility observed in the in vitro assays.