Zinfandel (also known as Primitivo) is a variety of black-skinned wine grape. The variety is grown in over 10 percent of California vineyards. DNA analysis has revealed that it is genetically equivalent to the Croatian grapes Crljenak Kaštelanski and Tribidrag, as well as to the Primitivo variety traditionally grown in Apulia (the "heel" of Italy), where it was introduced in the 18th century and Kratošija in Montenegro. The grape found its way to the United States in the mid-19th century, where it became known by variations of a name applied to a different grape, likely "Zierfandler" from Austria.