Physiological Events that Underlie Cell Death and Shrinkage in the Grape Berry

Abstract

Late-ripening berry shrinkage and mesocarp cell death of some Vitis vinifera L. varieties have caused increasing concerns in many wine regions worldwide due to the significantly decreased yield and deterioration of quality of both grape and wine. This can result in excess sugar accumulation, lower anthocyanins, poor flavour development (e.g., lower terpenoids) in grapes, and in wines, higher ethanol and more dead/stewed fruit characters. This phenomenon is variety-dependent, very typical in Shiraz, while it rarely occurs in Grenache. The underlying reason for this phenomenon remains elusive, with factors such as heat stress and berry hypoxia being suggested as potential contributors. The main aims of my research were to determine the physiological cause of cell death and berry shrinkage and to explore models to predict their occurrences. To examine in detail the berry microstructure (porosity) and oxygen concentrations in berries for Shiraz and compared to other varieties, based on the hypothesis that hypoxia in the grape berry is a contributing factor to cell death. To explore ways to ameliorate cell death and berry shrinkage in Shiraz, the effect of rootstock, bunch exposure and antitranspirants were trialled in my research.