According to the geographical distribution of the Vitis wild species, the vine subgenus Vitis subg. Vitis is divided into a European, an Asian and an American group. The Asian vines comprise about 30 species, several new species have been described from China in recent years. Important Asian wild vines are Vitis amurensis, Vitis coignetiae and Vitis ficifolia (also Vitis thunbergii). These are mainly found in China, Japan and Korea. They are less important for winemaking, but because of their high resistance to the hardest frost down to minus 35 °Celsius they are interesting for new varieties. The DNA structure of Asian vines consists of 19 chromosome pairs (2n = 38), which is why they can be crossed with all European and American vines without any problems. See also under vine systematics and wild vines.