The ultimate objective of this study is to develop a database of cold hardiness values for samples from the central coast region of California that can be used to develop a cold hardiness model. The model, taking into consideration the principle factors that influence grapevine cold hardiness, will be used to help growers predict the temperatures at which injury may occur. This will assist them in making decisions regarding their efforts to avert such injury through the use of wind machines, irrigation, and other vineyard management practices.
As of this date, this project has developed the necessary low temperature exotherm analysis system necessary to detect cold hardiness of grapevine buds and cane tissues. This has involved the acquisition and assembly of numerous electronic components and software to manage these components to enable the detection of the transition of the extra- and intracellular water in grapevine buds and cane tissues from a liquid to a solid state (ice). This transition is accompanied by the release of the heat of fusion. By using a computer-facilitated program to monitor the output of thermoelectric modules and the temperature in the freezing chamber, the low temperature exotherm event can be detected. The development of this system has unfortunately taken longer than anticipated and has only recently (December 18, 2001) been completed. Since this time, we have successfully identified the temperatures at which freezing of grapevine buds are occurring. We are now beginning to accumulate the database that will be necessary to develop the model.