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The utility of a given variety of grapes for wine making depends upon several factors. These include production factors such as scion-stock interrelationship, susceptibility to disease, inherent vigor of the vine, resistance to frost (which depends on the time of leafing out, the vine’s ability to produce crops after frost injury, and the like), and the yield and composition of the grapes under various soil and climatic conditions. One must also carefully evaluate: (1) the influence of environmental conditions (rainfall, wind, fogs, humidity, exposure, mean daily temperature, and time of maturity); (2) the adaptability of the must to various vinification and amelioration practices (temperature, type of yeast, aeration, and other variations); (3) the suitability of the wine for aging in the wood and in the bottle (rate of clarification, bouquet development, and resistance to disease); and (4) the basic quality of the wine produced by the variety. The production of wine may be considered as the complex interrelation, interaction, and mutual influence of all these factors with and upon each other. In order to study wine-grape-variety adaptation in California, one must consider each of these critically and separately.

The primary problem in enology is to determine the influences which affect the utility of a wine. Since grapes are the raw material, a study of the various varieties is the starting point. Because of the numerous variations in environmental conditions in California, the experiments must be repeated with each variety in as many different localities as possible.