Generally speaking, Saperavi and Rkatsiteli are most commercially used wines cultivated in Georgia. If we combine those two varieties, we will see that they comprise 85% of total wine harvest of Georgia.
There are three key reasons for Rkatsiteli's popularity. First strong resistance to cold winter weather conditions. Second is its ability to retain good acidity, even in the hottest summers. Third is its versatility; its balance of sugars and acids make it suitable for use in table wines, sparkling wines, sweet wines, fortified wines and brandy.
The reason why Saperavi is widely grown and cultivated is down to its high agricultural and technological properties (productivity, quality, frost-resistant). According to the chemical analysis, Saperavi belongs to a saint wine vines’ group. It is among the world's best red wines.
Now some more information about Saperavi and Rkatsiteli that you might find useful:
Rkatsiteli - Rkatsiteli plays a significant role in various former Soviet countries. In Ukraine and Bulgaria it holds the number one spot among white-wine varieties, more widely planted than any other, and it also has a respectable presence in Romania and Moldova. Armenia, also has a considerable acreage of Rkatsiteli.
Saperavi - grapes have spread to other regions of Eastern Europe more recently (Purcari, Moldova). Saperavi cultivars are also being grown in the U.S.notably in Finger Lakes, New York area vineyards. It has shown promising results for a few growers in Australia, where it was pioneered in the King Valley Region of North East Victoria.
Saperavi is also known under the synonyms, Kleinberiger, Nerki Khagog, Sapeavi De Kakhetie, Saperaibi, Sapeur, Sapperavi, Sapperavy, Scoperawi, and Szaperavi.
As for other European grapes with Georgian origin I should look this information with professional wine makers and I will probably need some more time. Though I have heard of Georgian origins of Japanese Koshu wine.
