Clonal Testing of Winegrapes in the San Joaquin Valley

Executive Summary: An on-going San Joaquin Valley wine cultivar clonal evaluation trial was initiated in 1986 and planted into the first trial block in 1987. Location is the University of California Kearney Agricultural Center, Parlier where cultural conditions and practices can be closely monitored. All of the selections are indexed FPMS sources, most of which are registered. None have ever been compared in clonal studies. Thus, industry would benefit from performance information on available selections. This study utilizes 15 single-vine replicates in randomized complete blocks for each cultivar. 1991 was the third year of comparison for three selections each of French Colombard and Chenin blanc. Each cultivar compares two different selections which are registered (indexed as virus free) but not heat treated. Additionally, each cultivar includes a heat treated selection. Thus, we are studying the possible influence of heat treatment on virus-free material of French Colombard and Chenin blanc. Barbera was in its first year of data taking. This compares an Italian selection, Rauscedo 6 (FPMS Clone 2), with Marshall (FPMS Clone 1). Barbera Clone 1 presently involves much of the present commercial acreage but was later found to contain mild leafroll. French Colombard. Clone 1 is the highest yielding, latest maturing, and most rot susceptible, possibly due to higher fruitfulness (cluster numbers and berries per cluster). Clone 5 tends to be the lowest yielding and earliest maturing selection over the three years of data taking. Presently, Clone 2 would appear to be the best overall selection. It is intermediate in yield and has favorable fruit composition characteristics. Interestingly, it is a heat treatment of Clone 1. Chenin blanc. Clone 5 produces the smallest berries and clusters of earliest maturity. However, yields are lowest and rot tends to be highest with this selection. Presently, Clone 4 would appear to be the best selection. It is the highest yielding and with the lowest rot incidence. This is a heat treatment of Clone 1 with more favorable vine yield characteristics. Barbera. These two selections were included to compare the widely planted Clone 1 (Marshall) with the only registered and recently introduced Clone 2 (Rauscedo 6). Because of its virus-free status, only Clone 2 should be recommended for planting at this time. However, its larger berry size and higher yields contribute to later fruit maturity and possibly lower anthocyanins per fruit weight. Further evaluation will be necessary to confirm this preliminary recommendation. Zinfandel was eliminated in 1991 due to inclusion of a misnamed selection. Grenache will be added with a comparison of three selections in 1993. Sanqiovese and Muscat blanc are also planned for future evaluation. Other cultivars will be added as promising selections become available. Wine samples will be made from French Colombard and Chenin blanc if full funding becomes available in 1992.