Defoliation and water leaf potential effects on oenological properties of Merlot (Vitis vinifera L.) grape must

This research was carried out to determine the effects of leaf water potential and defoliation treat-ments on the oenological properties of grape must. Merlot/41B graft combination grapevines were cultivated in Chateau Kalpak vineyards in Tekirdağ, Şarköy. The trial was carried out for two con-secutive years in the vineyard in the vegetation periods of 2019–2020 and 2020–2021. Leaf water potential treatments were S0 (Control =no irrigation), S1 (–0.3/–0.5 MPa), S2 (–0.5/–0.7 MPa) and S3 (<–0.7 MPa) and defoliation treatments were implemented as; Control(C), Full Window(FW), Right Window(RW) and Left Window (LW). As a result, the S2 (–0.5 MPa and –0.7 MPa) stress level resulted in more balanced responses, as seen in the combination of years in terms of both primary and secondary metabolites. The RW defoliation treatment may cause higher primary and secondary metabolite values in all criteria.