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Wine is usually made from one or more varieties of the European species Vitis vinifera, such as Pinot Noir, Chardonnay, Cabernet Sauvignon, Gamay and Merlot. When one of these varieties is used as the predominant grape (usually defined by law as a minimum of 75% or 85%), the result is a varietal, as opposed to a blended, wine. Blended wines are not considered inferior to varietal wines, rather they are a different style of wine making; some of the world’s most expensive wines, from regions like Bordeaux and the Rhone Valley, are blended from different grape varieties.[citation needed]
Wine can also be made from other species of grape or from hybrids, created by the genetic crossing of two species. Vitis labrusca (of which the Concord grape is a cultivar), Vitis aestivalis, Vitis rupestris, Vitis rotundifolia and Vitis riparia are native North American grapes usually grown to eat fresh or for grape juice, jam, or jelly, but sometimes made into wine.
Hybridization is different from grafting. Most of the world’s vineyards are planted with European V. vinifera vines that have been grafted onto North American species rootstock. This is common practice because North American grape species are resistant to phylloxera, a root louse that eventually kills the vine. In the late 19th century, most of Europe’s vineyards (only excluding some of the driest vineyards in Southern Europe) were devastated by the bug, leading to massive vine deaths and eventual replanting. Grafting is done in every wine-producing country of the world except for Argentina, the Canary Islands and Chile—the only countries not yet exposed to the insect.[31]
In the context of wine production, terroir is a concept that encompasses the varieties of grapes used, elevation and shape of the vineyard, type and chemistry of soil, climate and seasonal conditions, and the local yeast cultures. The range of possibilities here can result in great differences between wines, influencing the fermentation, finishing, and aging processes as well. Many wineries use growing and production methods that preserve or accentuate the aroma and taste influences of their unique terroir.[32] However, flavor differences are not desirable for producers of mass-market table wine or other cheaper wines, where consistency is more important. Such producers try to minimize differences in sources of grapes through production techniques such as micro-oxygenation, tannin filtration, cross-flow filtration, thin film evaporation, and spinning cones.