Clonal Testing of Wine grapes in the San Joaquin Valley

This is an ongoing study to evaluate promising, virus disease-free FPMS clonal material for the San Joaquin Valley. Completion dates for past trials were: French Colombard and Chenin blanc (1994), Barbera (1995), and Muscat of Alexandria (1997), Grenache (1998), and Muscat blanc (1998). The Sangiovese trial was completed in 1999 with crop level comparisons. Data collection began with the Chardonnay, Cabernet Sauvignon, Merlot, and Zinfandel/Primitivo trials. These trials were planted with 6 clones each in 1997 in order to evaluate clonal differences in a warm climate region. Sangiovese. Clones 2 and 3 are recommended for warm climate sites, while Clone 4 is not recommended. Clone 4 was consistently of poorer fruit composition (lower T A, higher pH and the most bunch rot), even with an imposed lower crop level; most often it was of lowest yield during the 5-year study period. The differences between Clones 2 and 3 were fairly clear in this study, each having certain advantages and disadvantages. Clone 2 was more fruitful and often ripened later than Clone 3 (-1.3 °Brix at harvest over 4 years). This later ripening can be corrected with crop level adjustment, as demonstrated in the 1999 comparative crop level treatments. Clone 2 had the smallest berries, even with crop level adjustment; Clone 3 berry weights were always heaviest, sometimes with fewer berries per cluster. Thus, mean cluster weights were similar between Clones 2 and 3. Overall, it would appear that Clone 2 is preferable due to its smaller berry size. However, its higher fruitfulness may require more attention to crop level management to assure timely ripening of quality fruit. Cabernet Sauvignon. Berry weight, number of berries per cluster and cluster weight differences significantly influenced clone yield which, in turn, affected fruit soluble solids at harvest. Clones 8 and 22 were highest yielding, while Clones 2 and 24 were lowest; Clones 10 and 21 were intermediate. Clones 2 and 24 had the smallest berries and fewest berries/cluster. Merlot. Vine yields and cluster weights were similar among clones, and fruit composition and berry weight differences were minor. Zinfandel/Primitivo. The Zinfandel clones were all similar except for the smaller berries of Zinfandel 2; Zinfandel 3 had a lower bunch rot incidence as compared to Zinfandel 1 A. The Pnmitivo clones did not differ from one another. However, when compared to Zinfandel the Primitivo clones had smaller berries, fewer berries/cluster, and clusters of lower mass and earlier ripening and less rot (~3x less). Yields of Primitivo tended to be lower than those of Zinfandel. 54 Project Title: Clonal Testing of Wine grapes in the San Joaquin Valley (Continued) Chardonnav. Clone 4 was highest yielding, while Clones 6 and 37 were lowest, mainly the result of number of berries/cluster and cluster weight. Berry weight was highest in Clone 20 and lowest in Clone 4. Clone 4 had lower fruit soluble solids but higher TA and pH at harvest. The 1999 results of the ‘fighting varietals” – Cabernet Sauvignon, Merlot, Zinfandel and Chardonnay are preliminary, as they represent first crop data. However, it is interesting to note that significant clonal differences are demonstrated early in the study when crop levels are adjusted uniformly across clones for each cultivar. Thus, the differences reported are mostly the result of berry weight, berries/cluster and the final cluster weights.