Effects of early water stress levels on berry set and berry development in Merlot cv. (Vitis vinifera L.)

Early water deficit at flowering results in poor berry set or aborted grape yield reduction. The main aim of this study was to find out the effects of water stress levels on berry set and embryo berry development. This study was carried out in Montpellier using by ECOTRON System, SupAgro/INRA, France. Seven years old Merlot / SO4 grafting combination was used as a plant material. Potted grapevines were grown under natural conditions in open field. A randomized block design was used with 3 replications and each parcel had 2 grapevines and 4 water stress levels. Stress Levels were WS0 (control) 0; -0.2 MPa, WS1 -0.2; -0.4 MPa, WS2 -0.4; -0.6 MPa, and WS3 -0.6; -0.8 MPa, respectively. The stress period was started in the second week of May in the 17th E-L stage and ended in the second week of June in 27th E-L stage. Flower samples from clusters were collected in three days intervals and samples were examined by Technovit method. Under this early water stress conditions, the pollen viability and pollen germination ratios were not affected, but berry set ratio, phenologic stages and berry development were negatively affected. It was determined in Merlot cv. early water stress (between 19th to 29th stages) should be avoided especially when psi(pd) values decrease below -0.4MPa