Evaluation of winegrape clones
The Zinfandel clonal trial was terminated with only minor differences being found among certified Zinfandel clones. However Primitivo was different from the Zinfandels in having lower yield per vine due to smaller clusters, fewer berries/cluster and smaller berries. Sangiovese clones also differed significantly. Sangiovese 3 showed a trend towards lower yield and had significantly fewer berries per cluster. There was also a trend towards lighter clusters but it was non significant. Clone 3 also had slightly advanced maturity with 0.7 higher °Brix and 0.07 higher pH, although the acidity did not differ. Cabernet Sauvignon clones in the Napa hillside site show similar trends to previous AVF-funded work. FPMS 6 is the lowest yielding clone, with 2 and 5 being intermediate and 8 highest. Yield differences are due primarily to cluster wt. For Pinot noir, the range in yield was about 2-fold from 11.7 lbs/vine (5.1 tons/acre) for UCD1 to 22.3 lbs/vine (9.7 tons/acre) for UCD 31. Again in 1994, harvest date which stretched over 10 days, was correlated strongly with yield/vine. Yield differences were made up, again, of a complex combination of cluster number, berries/cluster and berry wt. Largest berries are seen in UCD 23 and 31, and ESP 374. Smallest berries were found in UCD 13 and the “Wente” selection. Clonal evaluation work in continuing on Zinfandel, Merlot and Malbec. Recently concluded and published clonal evaluation work can be found in Practical Winery & Vineyard, American Vineyard and the American Journal of Enology & Viticulture