Development of models for predicting phenology and evolution of maturity in cv. Cabernet Sauvignon and Chardonnay grapevines

A study was carried out to develop predictive models for phenology and evolution of maturity in wine grapes ( Vitis vinifera ), in a vineyard located in the "La Oriental" farm in the Talca Region (35º 27' S lat. and 71º 37' W long.) during the 1998/99 growing season. To this end, measurements were made of the number of leaves, length of buds, diameter of berries, soluble solids (SS), total acidity (AT) and pH for grapevines cv. Cabernet Sauvignon and Chardonnay. To develop the prediction models for phenology, soluble solids, and pH as a function of the accumulated degree-days (base temperature = 10ºC), Mitscherlich's monomolecular equation, which assumes continuous growth, was used. In the case of the total acidity model, an exponential equation with a negative slope was used. The results of this investigation indicated that the use of accumulated degree-days could be a good tool to estimate phenological events and the evolution of maturity in Cabernet Sauvignon and Chardonnay cultivars. In this respect, the predictive models for phenology, soluble solids and total acidity had coefficients of determination (R 2 ) greater than 0.88. The lower correlation was found in the pH model for Cabernet Sauvignon (R 2 =0.71)