Evaluation of Five Merlot Clones in the Napa Valley over Two Vintages.

Five Merlot clones (FPMS 1, 3, 6, 8, 9) were evaluated at the UC Davis Oakville Experimental Vineyard in 1995 and 1996. A randomized complete block design was used with Teleki 5C rootstock (Vitis berlandieri x V. riparia) with 1.8 m x 2.4 m spacing and bilateral cordon training. The plots were replicated eight times, each plot contained 3 rows and 9 vines, giving a total of 216 vines per clone. Yields, cluster weights, and berries per cluster were significantly different in both years. In 1995, the yield differences among the clones were correlated with cluster weight (r=+0.989) and the number of berries per cluster (r=+0.988). In 1996, cluster weight, berries per cluster, and cluster number (r=+0.939) were highly correlated with yield. Significant differences were found with regard to �Brix, pH, and potassium (K+) in both years. The highest juice K+ and pH values in both years were found with FPMS 8. Berry skin extracts revealed no significant differences in total phenols or total anthocyanins. FPMS 9 exhibited the lowest concentrations for free and co pigmented anthocyanins, and the second lowest for polymeric anthocyanins in 1995. In 1996, FPMS 9 had the highest concentrations of free, co pigmented, and polymeric anthocyanins. The lowest free and co pigmented anthocyanin concentrations in 1996 were found with clone 3. Total color ranged from 5.19AU to 7.42 AU in 1995 and from 6.78 AU to 8.08 AU in 1996. The total phenol content followed a similar trend with FPMS 9 the significantly lowest value (30.1 AU) 1995 and the highest value (44.2 AU) in 1996. Preliminary differences in sensory evaluation were observed in an informal bench tests.