Researchers are testing new and existing wine grape varietals and clones for their suitability to the San Joaquin Valley to help growers make the best selection for new and replanted vineyards.

Interest in new materials for the Valley is on the rise as demand for lower price-point wines made from SJV grapes continues to climb. Information on those trials was shared at a research road show in Fresno hosted by the San Joaquin Valley Winegrape Growers Association.

Mathew Fidelibus with the UC Davis Viticulture and Enology Department is looking at dozens of clones for several popular Valley varietals in an effort to provide growers greater choice. He said clonal selection is just as important as varietal when it comes to making decisions about what to plant.

“If you are planting a new vineyard and you know you’re going to have rot problems, for instance, you won’t have to worry about that if you pick the right clone,” said Fidelibus, who is based at the UC Kearney Research Center in Parlier. “The clone makes a big difference.”

He is continuing work started decades ago by retired UC Cooperative Extension viticulturist Peter Christensen to evaluate a number of clones for yield, fruit composition and susceptibility to pests and diseases to help growers sort through the selection process.

Fidelibus is comparing clonal selections of Cabernet Sauvignon, Chardonnay, Barbera, Merlot, Syrah and Zinfandel for suitability to the San Joaquin Valley.

Many of those clones are recent releases from the Foundation Plant Material Service at UC Davis, which screens and registers hundreds of grape selections for pests and diseases so that growers can ensure they are buying clean and consistent stock.

Barbara is an increasingly popular blending varietal for the San Joaquin Valley, where about 90 percent of the 7,500 acres currently in production statewide are grown. There are now several registered clones in California. The first was FPS 1, which was retired in the 1990s due to its high leafroll susceptibility and replaced with FPS 2. However, FPS 2 is susceptible to sour rot in the Valley due to its large berries and late maturity. As a result, Fidelibus called FPS 2 the “worst choice” for Valley Barbera growers.

FPS 6 has since been released as a “clean” version of FPS 1. Growers also have three “Torino” Barbera clones available as FPS 3, 4 and 5. Fidelibus said FPS 3 and 5 have the highest yields with big clusters of smaller barriers. Their late maturity does leave some susceptibility to sour rot but not to the degree of FPS 1.

“These would be a good selection to use in an area where sour rot is not an issue or you can control berry size by withholding irrigation,” Fidelibus said.

Barbera FPS 4 provides lower yields with fewer berries per cluster, but is less susceptible to sour rot. Fidelibus said FPS 6 is probably the best general selection because it provides comparably moderate yields, but less sour rot susceptibility than other clones taken together.

“We think FPS 4 is probably the best Torino clone for the Valley, but in the end we are recommending FPS 6,” he said.

For Chardonnay, he said FPS Clone 4 provides good yields, large clusters and good fruit composition, but again is highly susceptible to sour rot.

“The clone has big, full clusters so sour rot again is the limiting factor here,” he said.

Clone 15 provided about 10 percent fewer yields, but less sour rot incidence, and therefore produced a larger harvestable yield in Fidelibus’ trials.

Merlot is another important Valley varietal. While only 20 percent of the merlot acreage is produced in the Valley, the area’s high yields result in almost half the harvested crop statewide coming from San Joaquin Valley vineyards. Fidelibus is still looking at a number of clones against the standard FPS Clone 3, which has provided consistent fruit set, yield and fruit composition.

Clone 10 performed the best in side-by-side trials, producing consistently higher yields and relatively low pH. He said Clone FPS 11 was the most undesirable for its large berries and high rot incidence. Clones 3 and 9b performed similarly to 3, but overall, Fidelibus said 10 provides probably the best alternative to 3.

Fidelibus is also looking at about 10 different selections of Syrah, but has only preliminary data with no definite recommendations because the trial is still relatively new. He is comparing several California Syrah selections against Australian Shiraz clones as well.

“We are seeing that Shiraz selections 1, 3 and 7 grouped together have higher soluble solids and pH, smaller berries, smaller clusters, lower yields and less sour rot than the Fresno selections,” he said.

Jim Wolpert, UC Davis viticulturist, is conducting screening trials to compare varietals that are new to the San Joaquin Valley, but may be well suited to the area’s climate and growing conditions. The trial was initiated in small-scale plots at Kearney in 2002 and recently expanded into larger screening trials.

The first trial looked at 20 different red varieties from around the world, and has since expanded to include a similar number of white varieties. Wolpert is evaluating these varietals for factors such as harvest date, brix, yield, and pH to assess which varieties and cultivars are suitable to the San Joaquin Valley.

He said there is an enormous pipeline of material from all reaches of the globe waiting to be evaluated by FPS, which will ultimately result in a number of new choices for San Joaquin Valley growers.

“The reason we are where we are right now with all these varieties is thanks to FPS,” Wolpert said. “The foundation releases 50 to 100 materials a year, new varieties and clones of existing varieties and they are just scratching the surface of evaluating those new plant materials.

“We are really excited about the possibilities,” he added. “It may be a little bit like looking for a needle in a haystack, but we think it’s an important search.”

Wolpert expects a number of new clones and varietals suited for the San Joaquin Valley to be available by 2012.

In the meantime, he is hoping to generate an online database for information on wine grape plant materials where growers and nurserymen can go as a “one-stop-shop” for data on clonal and variety selection.

“A lot of this material is scattered about,” he said. “What we would like to be able to do is provide a venue where someone can go to one place and type in Chardonnay, for instance, and get all the information about Chardonnay varieties and clones for each major growing region.”

Ron Brase, of California Ag Quest and secretary of the SJV Winegrape Growers Association, said work on new clonal and varietals selections is very important to San Joaquin Valley grape growing.

“We’ve got a big investment in planting these vineyards, and we don’t want to make an investment only to find we have leafroll or sour rot problems down the road,” Brase said. “The work we are talking about is being done at Kearney, so it’s San Joaquin Valley specific information.”