The joining of the bud from a desired fruiting variety (scion) to the stem of another variety (rootstock) chosen for characteristics such as resistance to phylloxera and adaptation to soils and climate. The grapes and wine of
grafted vines retain the organoleptic characteristics of the scion. Below the graft union (where the scion and rootstock are joined) the resistant roots come from the rootstock variety.
Grapevine Vitis species are able to cross-pollinate both in nature and with deliberate human intervention. The pollen from a male variety is applied to the pistil of a female variety to create seeds in the grapes. Each seedling is a unique genetic combination that makes a new variety. This is an ancient process in nature and not a laboratory process like GMO. If that variety is found to be desirable, it is propagated by vegetative means, usually byrooting cuttings from the mother vine.
Hybrid Producer Direct
These are multi-species grapes between European and American Vitis that can sometimes be grown without grafting (ex. Clinton, Jacquez, Cunningham, Concord).
Grapevine phylloxera (Daktulosphaira vitifoliae) is an aphidlike insect that feeds and forms galls on the roots and leaves of North American grapes causing little damage. However, the soft roots of Vitis vinifera did not evolve to tolerate this feeding and its root will decay leading to vine death.
Called mildiou in France this is a disease caused by the fungus Plasmopara viticola that is indigenous to North America where the native vines have developed a tolerance for it. When it travelled to Europe in the 19th century, it caused enormous damage to the crops, esp. those in the regions with high humidity and summer rainfall. French scientists found that spraying the vines with various formulations that included copper sulfate was an effective control.
Another North American fungus (Uncinula necator) that became a blight in vineyards planted to European vines starting in the 19th century. Unlike downy mildew, this fungus does not need rainfall to reproduce and spread in vineyards so it is the main fungal problem in Meditarranean climates. The earliest method of control was to protect foliage and fruit with
Acronym of the German word "Pilzwiderstandsfähig", literally meaning "capable of resisting fungi". Grape varieties resistant to vine diseases are therefore grouped under this name. Resulting from multiple crosses between noble grape varieties and more rustic, even wild vines, these new grape varieties benefit from a natural resistance to the most devastating diseases of the vine, namely mildew and powdery mildew.