It's relatively easy to determine whether a vineyard is a raisin, wine or table grape vineyard based on its trellising system and the geographic locations of the vineyard, but it is virtually impossible to determine variety.

The grower who planted the vineyards certainly knows, but to a potential buyer or anyone else who needs to confirm grape variety only DNA testing offers reliable confirmation.

Now for the first time in the U.S. DNA testing to determine vine variety is commercially available.

Carole Meredith, professor in the Viticulture and Enology Department at the University of California says her lab is now expanding its DNA analysis service to private parties who require objective varietal identification of grapevines.

Although several research laboratories in several countries can DNA type grape vines, a commercially available variety identification service has only been available from the Australian Wine Research Institute. However, that services has been suspended due so sample preservation and shipping problems along with Australian plant importation regulations and a limited reference database of varieties.

Here are the particulars of the UCD service: In a uniform vineyard of unknown identity, Dr. Meredith recommends testing two or three vines. In a mixed vineyard, test at least one vine of each type. Lab technicians prefer to work with tiny leaves at the shoot tip, while the shoot is still actively growing. However, older leaves and other tissues can be used, if necessary.

Dry leaves chemically

The lab provides materials that are used to quickly dry the leaf samples chemically. Not only does this process preserve the DNA in excellent condition and eliminate the need to keep the samples chilled and moist, but also the samples are dead and thus not subject to federal quarantine regulations governing the importation of living grapevine tissue.

The lab identifies varieties by comparing the DNA profile of the sample to its database of more than 700 grape varieties, the largest database in the world. It includes all the wine, table, raisin and rootstock varieties grown in California and most of the varieties grown in other major viticultural regions.

The cost of this service is $300 per vine. This is comparable to the $455 Australian charged by the Australian Wine Research Institute.

For more information or to arrange to have vines tested, contact Gerald Dangl (530) 752-7540 gsdangl@ucdavis.edu