American varieties

American varieties like Vitis Labrusca, Vitis Berlandieri, Vitis Ruperstris, etc. are used as a stock.
These American stocks are resistant to most from grapelice, a disease taken from America which damages the roots of the plant.

The grape variety, meaning the flavour of the wine is determined by the bough, the grapevine growing from the stock.
For all the wines in the world (with a few exceptions) it is a European variety.