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

•Deficit irrigation (35% ET0) does not reduce stem water potential (Ψstem) below water stress levels in Merlot Khorus.•Stomatal conductance (gs) and net photosynthesis (AN) are negatively affected by deficit irrigation in Merlot Khorus.•The basal crop coefficient (Kcb) of Merlot Khorus in northeast Italy is far different from what suggested by standard methodologies.•Merlot Khorus is suitable for deficit irrigation management.