In the second half of the 19th century, a dangerous aphid caused a catastrophe in Europe: the phylloxera. It attacked the roots of the vine and destroyed most of the entire European vine population within a few decades.
In America, on the other hand, the phylloxera has been around for millions of years. The vines there have developed a resistance to phylloxera and are immune to it. At the end of the 19th century, European vines began to be grafted onto the resistant lower parts of the American vines. This procedure is called vine grafting.
With very few exceptions - ungrafted Vines - grafted vines are therefore found in Europe's vineyards today.