Yield and yield components and juice chemistry data were taken on 15 clones of Cabernet Sauvignon, comprised of five long-held selections from UC Davis Foundation Plant Services, our newer selections arriving from California or as importations from Italy and France, and three California ?Heritage? selections. Also planted in the experiment were the three Heritage clones with their original virus infections, to be contrasted with their now-available clean counterparts.
Second year data were taken in 2006 showed similar trends to the 2005 data with significant differences in vine yield components among clones. One Italian selection (FPS 27), one Heritage selection (FPS 29-Niebaum Coppola) and the French selection (ENTAV 169) respond more like high-yielding FPS 14 (Chile). In contrast, the new California selection (FPS 24), second Italian selection (FPS 26) and Heritage selection FPS 30 (Disney Silverado) were more like moderate yielding selections FPS 2 and 4. The third Heritage selection (Mondavi To-Kalon) was the most interesting new selection in that it yielded the lowest, slightly lower than low yield standard FPS 6.
Virus-infected selections contrasted with their clean counterparts showed significant yield reductions in two comparisons, while in the third it was a small difference. However, all virusinfected selections, despite already having lower yields, were severely delayed in ripening. The difference in ripening was as much as 4 Brix lower in diseased materials. These of new materials are ready for winemaking in 2007.
One important outcome of the trial in 2006 was the appearance of virus-like symptoms (red leaves) in healthy vine treatments adjacent to virus treatments. Evidence is mounting in Napa that LR virus is spreading, likely as a result of the feeding activity of mealybugs. Obviously, a comparison of infected and healthy treatments is valuable only if the healthy vines remain so. The apparent movement of virus jeopardizes all of the remaining healthy clones not just the virus vs non-virus comparisons. Because this risk is great, and the data comparing virus and healthy is sufficient to draw conclusions, the virus-infected treatments will be removed in late winter 2007.