Physiological characterization of Vitis hybrid cv Merlot Khorus under two different water regimes in northeastern Italy

Fungus-resistant varieties are gathering attention all over viticultural areas owing to their contribution to sustainable management. Sustainable viticulture implies lower inputs in terms of pesticides and water. However, investigations on the physiological behavior of fungus-resistant varieties under drought stress have been seldom conducted so far. Under climate change conditions, evaluating precise water use is particularly important to set up proper irrigation. In this study, a two-year experiment was imposed to characterize the physiological behavior of the fungus-resistant variety Merlot Khorus under two contrasting water regimes (full irrigation, WW; water deficit, WD). Berry weight and grape quality in the two treatments was also compared to evaluate the feasibility of adopting deficit irrigation strategies in the region. The study was conducted in the Friuli Venezia Giulia region (Italy). The measured values of stem water potential (& psi;stem) did not highlight any severe water stress (> -1.15 MPa) in WD. However, gs and AN decreased to values typical of drought-stressed vines. Concurrently, the experiment assessed that the calculated Kcb of Merlot Khorus in northeast Italy is far different from what has been suggested by standard methodologies and the literature. The grapes under deficit irrigation showed reduced berry weight, while basic maturation parameters and anthocyanins were improved. Overall, the study indicated that Merlot Khorus appears to be a genotype suitable for dry farming or deficit irrigation management in northeastern Italy. Therefore, the results may help winegrowers to improve irrigation strategies.