Evaluation of New Winegrape Varieties for the San Joaquin Valley
A wine grape variety trial was established at the Kearney Research and Extension Center, a warm climate region. The trial consists of 55 16-vine plots, each planted to a different red or white wine grape variety selected from warm-climate Mediterranean regions. Most of the varieties tested were recently released to the industry from Foundation Plant Services so, in many cases, certified selections of these varieties have never been evaluated in California. All vines were spur pruned, leaving 8 or 9 two-bud spurs per meter of cordon.
We attempted to harvest all white varieties at 22 Brix, and reds at 24 Brix, though inclement weather forced the harvest of a few slow ripening varieties in early November, before they were completely ripe. At harvest, yield components, rot incidence, and basic chemistry were determined and, for 25 of the 55 varieties, wine lots were made at Constellation Brand’s experimental winery.
The varieties were harvested across a wide range of dates starting with a white cultivar, ‘Fiano’, on 18 August, and ending with 15 red and white varieties which were harvested in the first week of November. Yields ranged from a meager 2.32 kg per vine from the red cultivar Carmenere, to more than 35 kg of fruit per vine from the white cultivar ‘Trebbiano Toscano’. Harvest date was poorly correlated with yield, but there was a relatively strong positive correlation between rot incidence and harvest date.
Yield of red and white varieties was more strongly correlated with cluster weight than with the number of clusters per vine, and cluster weight was more strongly correlated with the number of berries per cluster than with berry weight. Red and white varieties varied widely with respect to pH and titratable acidity. Other fruit composition data were collected by Constellation and will be shared in a future report. Wines from the trial will be made available for tasting and analysis in 2012.