Effects of water stress on vine growth, yield and grape quality of some table grape varieties

In this thesis, the effects of different irrigation treatments on vine growth, physiological activities, yield and quality parameters of table grapes were investigated in Manisa conditions. Research was carried out in the experimental vineyards of Siyah Kişmiş, Sultani Çekirdeksiz and Crimson Seedless table grape varieties grafted on 1103 P rootstock in Manisa Viticulture Research Institute. Experiment was conducted for three consecutive (2015-2016-2017) years and three different irrigation levels were applied with subsurface drip irrigation system in the research; namely Full Irrigation (Control: FI), Stress 1 (Mild stress: FI x %65) and Stress 2 (Severe stress: FI x %35). The parameters such as leaf water potential and stomatal conductance were examined in addition to yield and quality criterias and physiological reactions of the cultivars against the applications were monitored. The effects of irrigation treatments on yield values of years average were found statistically significant in Siyah Kişmiş and Sultani Çekirdeksiz varieties. It was determined that yield values of Siyah Kişmiş obtained by Full Irrigation were 11% and 18% higher than Stress 1 and Stress 2, respectively. On the other hand in Sultani Çekirdeksiz variety, these increments were found 7% and 22%, respectively. When the effects of treatments on berry composition were examined, significant differences were found. Also it was determined that some of the bio-active compounds such as total anthocyanin content, total phenolic compounds, total flavonoid content, antioxidant capacity and maturity criterias were increased with water stress. Additionally it was found that colour index of red grapes (CIRG Index) values increased with deficit irrigation treatments. It was observed that the mid-day leaf water potential (Ψmd) values decreased (stress level increased) in all varieties due to water stress. The lowest Ψmd values were obtained from Sultani Çekirdeksiz variety with -1.75 MPa. On the other hand as the water stress level increaesed, the stomatal conductance results were decreased. In this direction, it was determined that the varieties used in the research were classified as anisohydric plants. As a result, in order to ensure optimum yield and quality in Manisa conditions, it was determined that table grape growing without irrigation was not suitable and also it was determined that the irrigation requirement of the grapevine should be fully supplied during the growing season for high grape yield. When the water foot print and functional food concepts were taken into consideration, water deficit treatments (Stress 1 and Stress 2) became prominent due to the use of less water and higher nutrient content of the grapes obtained. Therefore it was found that Stress 1 (Mild stress) treatment was more favorable in order to reduce the water consumption and provide optimization between yield and quality.