Evaluation of new Winegrape Varieties for the San Joaquin Valley

A wine grape variety trial was established in 2008 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 selection originating from warm-climate Mediterranean regions, and/or believed to have traits that would be desirable in a warm climate wine region. Most of the selections tested were recently released to the industry from Foundation Plant Services so, in many cases, certified selections have never been evaluated in California. All vines are on 1103P rootstock and in 2011 and 2012, the first two cropping years, all vines were spur pruned, leaving 8 or 9 two-bud spurs per meter of cordon; in 2013, certain varieties were subjected to simulated machine pruning, or cane pruning.

In general, we attempted to harvest all white varieties at 22 Brix, and reds at 24 Brix, but certain selections were picked at higher or lower Brix depending on a number of factors, including the desired wine style. At harvest, yield components, rot incidence, and basic chemistry were determined and 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, in early August, and ending with about a half dozen red and white varieties that were harvested on the last day of October. Yields ranged from less than 6 kg per vine for Prieto Picudo to more than 50 kg of fruit per vine from the machine-pruned Tocai fruliano, a white cultivar. Red and white varieties varied widely with respect to harvest date, pH, and titratable acidity. Berries from red varieties also varied widely in their content of anthocyanins, tannins, and other phenolic compounds.

Most varieties had slightly higher anthocyanin content in 2013 than they did in 2012, and Bonarda and Segalin noir have consistently had the highest anthocyanin content of the varieties tested. Wines from the trial will be made available for tasting and analysis in 2014, as they have been in each of the past several years. Twelve varieties which performed very poorly in 2011 and 2012 were topworked to new selections in 2013, and some varieties were subjected to different canopy management practices to determine if yield and rot problems could be ameliorated. Shoot tucking generally had little if any affect on fruit quality or rot, but simulated machine pruning greatly increased yields and reduced rot of most varieties subjected to this practice. Additional years of data are needed to determine if the high yields of machine-pruned vines are sustainable and whether or not they adversely affect fruit or wine quality.