Viticulture is the art and science of vine-growing and grape-harvesting. In general, the portions of our planet lying between 20° and 50° latitude on either side of the equator (Figure 1.1) are considered suitable for the vines. In these temperate climates, the tilt of the earth’s axis in relation to the sun results in temperatures in the Northern hemisphere in March (and the Southern hemisphere in September) that rarely fall below about 50° Fahrenheit (F) (10° Celsius [C]). As analytical chemistry and possibilities for genomic and epigenomic analysis have evolved, it has become possible to begin to monitor and understand, in detail, how climate affects wine production. For example, a recent Italian study investigated the changes, over a three-year period, in phenotype of a Vitis vinifera cultivar by looking at the transcriptome. They found that most responses they could follow could be attributed to local early spring weather patterns. While a complete analysis was not reported, it was concluded that weather patterns in the previous year were correlated with current year growth. Much of the biology for raising grapes has been discussed, and while 80% of the world’s grape crop is used for production of wine there have been and remain formidable technical difficulties in breeding grapevines. Part of the breeding problem derives from the fact that grapevines are highly heterozygous outcrossers, and so they do not breed true from seed. But they are good cultivars and are polygenic (poly = many; genic = genes). Their inheritance appears to be controlled by large numbers of genes of minor effect. As a consequence, traditional cultivars, grown in their accustomed places, appear to possess subtle combinations of genes whose totality can be preserved by grafting techniques but not in other ways. That is why it appears that the wines produced by such longstanding and traditional cultivars in the hands of vintners accustomed to their nature have unique characteristics of style and quality. Indeed, it seems that it is largely to encourage and maintain such subtle differences that grapevines are seldom propagated from seedlings (but see below) unless a “new” variety is sought by breeders.
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