Identifying Varieties and Clones by DNA Typing

We continued to investigate possible ways to distinguish clones within important winegrape varieties. We tested a method called ISSR and were able to detect some differences in Chardonnay and Pinot noir clones but they were not sufficiently reproducible to be useful. We also tried a selection of new SSR markers developed within the Vitis Microsatellite Consortium and found that 8 of 12 markers we tried could detect some differences between clones of Chardonnay or Pinot noir or both. We obtained and analyzed 150 accessions of Plavac Mali from Croatia for comparison with Zinfandel and found that Plavac Mali is not Zinfandel, contrary to some opinions. Surprisingly, we also found that Plavac Mali is not a polyclonal variety as we had presumed and that the accessions were almost completely uniform in their DNA profile.