Twenty wine grape varieties common in Southern Europe that might add something special to wines made from San Joaquin Valley fruit are being evaluated at Parlier by University of California (UC) viticulturists and enologists.
A recent grape day at the Kearney Agricultural Center included a tour of the test plots where the vines are being observed for how they perform in the valley’s warm climate, including fruit color and acidity, water-use efficiency, and other traits. Yields and wine quality will be assessed in the future on promising candidates.
The project is supervised by Jim Wolpert, chairman of the Department of Viticulture and Enology at UC, Davis. Wolpert’s research assistant, Mike Anderson, discussed the progress of the effort, funded by the USDA Viticulture Consortium and the American Vineyard Foundation, during the gathering.
Anderson noted that new, alternative grape varieties might help the SJV work out of the economic slump brought on by over-production, higher quality expectations of consumers, and competition from imports.
Consumer interest in varietal labeled wines caused a decline in generic wines and acreage of traditional SJV varieties such as Chenin Blanc, French Colombard, Grenache, and Carignane, while Chardonnay and Merlot gained favor with consumers.
And, Anderson said, quality of Chardonnay and Merlot grown in the SJV does not measure up to that from coastal counties.
At the same time, interest in alternative cultivars is increasing globally and in California as indicated by additional varieties reported in annual wine grape acreage reports.
Among the varieties in the Parlier trial are Aglianico, Montepulciano, Cinsaut, Souzao, Petit Verdot, Tempranillo, and Durif. Several are new clones from California vineyards. Tempranillo and Durif, also known as Valdepenas and Petite Sirah, respectively, have been grown in the SJV.
The plot is planted 10 by 6 feet on a two-wire trellis with four replications. All vines are on 1103 Paulsen rootstock planted in June of 2003 and budded in May of 2004.
According to Anderson, although the project is not funded for trial winemaking, Constellation Brands Inc. in Madera has agreed to do phenolics and other analyses on this year’s crop.
Wolpert said earlier that California winemakers are looking for something new, but some fear typical wine consumers will be reluctant to try unfamiliar and hard-to-pronounce varietals.
But others in the wine industry suspect that European varieties, if they can be grown successfully in the SJV, might provide blending components to enhance flavors and differentiate brands.
Added in small amounts, they would still allow use of a familiar varietal designation on the label. This, Anderson said, is already being done with Rubired for red wines and Muscat varieties for whites.
For the moment, he said, the Parlier plot “will initially focus on evaluating what characteristics a cultivar can add to existing popular cultivars.” The marketplace could then dictate the acceptability of alternate cultivars as future varietal labeled wines.
“We can learn the basics of each variety here, and then if interest continues, we find a variety’s potential and then adjust rootstock, irrigation, or trellising to deliver what’s desired,” Anderson said.
Findings from the project, he added, could mean substantial savings to California growers looking for something new.
He cited unsuccessful and costly experiments with the Sangiovese variety in California. “It was popular for a while, but acreage is dropping rapidly now. Maybe instead of growers spending millions of dollars experimenting on their own, we can spend a few hundred thousand and learn something about these varieties.”
Raisin grape growers at the event took notice of the project headed up by Matt Fidelibus, UC Extension viticulture specialist at KAC in Parlier, using abscission agents to assist in continuous-tray mechanical harvesting of raisins.
Abscission agents applied to grapes cause berries to loosen from the clusters and are being studied as an alternative to cane cutting.
In the continuous tray method, canes are cut, or harvest pruned, about 10 days before harvesting to dry up the clusters so berries will fall off.
In practice, however, some canes may be overlooked, and some berries are broken, or without cap stems, and juice freely when separated from clusters. Juicing attracts harmful insects and causes the berries to pick up sand and debris.
Fidelibus last year screened various compounds and found that methyl jasmonate, a natural plant hormone, and coronatine, a related chemical, were the most effective in causing grape berries to separate from clusters. The materials are not registered for this use.
Fidelibus found that most of the berries treated with the two compounds detached at the pedicel, or stem, leaving only a dry scar on the surface of the berry. In contrast, berries in the harvest pruning process generally retain stems that must be removed at a packing house and diminish raisin quality.
“We anticipate,” Fidelibus reported, “that raisins made from grape vines treated with methyl jasmonate or coronatine will not have any cap stems to remove. Thus, application of these abscission agents may facilitate the harvest of individual berries having minimal mechanical damage.”
His current studies are aimed at finding the optimum rate of the agents to cause the release during mechanical harvesting but without the berries falling off on their own.
Mike McKenry, UC nematologist at KAC, reported on his experiments with Roundup applied to old grape vines to kill their roots to a depth of five feet as a means of controlling rootknot nematode.
The process is then to drench the soil profile with less volatile nematicidal agents and plant new rootstocks having broad and durable nematode resistance.
“The idea is to starve the soil ecosystem with Roundup and a nematicide, wait one year, and then switch to a different rootstock with broad nematode resistance,” McKenry told the grape day visitors. Rootstocks that are promising for this use include RS3, RS9, and 1017A.
This is his approach after working with nematode control measures on trees and vines for many years. He said one local grower painted Roundup on Thompson Seedless and Ruby Seedless and gained complete root kill in three years, and he hopes to accelerate the process.