Can lesser-known European varieties improve returns for the San Joaquin Valley wine grape industry?
That's what University of California viticulturists want to find out from trial plantings at the Kearney Agricultural Center (KAC) at Parlier.
James Wolpert, Extension viticulturist at UC Davis, and his colleagues believe European varieties could add color, tannins, flavor and other traits to improve quality and consumer acceptance of wines made from SJV grapes, elements particularly important in view of heavy competition from imports.
In 2003, 20 varieties, blacks and whites, originally from Southern France, Italy, Portugal, and Spain and having names such as Grenache noir, Montepulciano, Touriga Nacional, and Tempranillo, were set out at the Parlier site on 1103P rootstock.
In 2008, 1103P rootstock was planted for a second phase of nearly 60 European blacks and whites to be budded during 2009 and 2010. Their names, ranging from Albillo Mayor and Forastera to Counoise and Touriga Brasilieira, are likely new to most growers and all but a few domestic wine consumers. They also include 11 patented varieties.
Showing the plantings during a field tour at the Grape Day 2009, Wolpert said, “Most of these are not really ‘new.' They've been around for quite a long time, and some have been tested in the Valley before. Some deserve another chance because we are using new trellising designs and drip irrigation and because the earlier vines may have had viruses. They are certainly virus-free this time.”
The idea for the trials, he said, came from industry. “We've been hearing from people that some places where they are growing Cabernet Sauvignon, Merlot, and Zinfandel could use more ‘interest' in their wines.”
Although those wines “are okay, the marketplace is now demanding more character that we may be able to find by blending with the European varieties,” he added. This has already been done in the case of a bit of Muscat of Alexandria being added to Cabernet Sauvignon for a wine with something different.
Wineries are reluctant to add new European variety labels unfamiliar to consumers and prefer to stay with the popular standards, enhanced by blending.
Wolpert said the number of European varieties in the evaluations is high because of the success of Foundation Plant Services at UC Davis in providing clean stock of varieties numbering in the hundreds, if not thousands, from around the world.
“In these trials we are looking for good yields, of course, and, obviously, a variety has to have good color, tannins, acid, and sugar — all the things a winery would expect,” he said.
“But winemakers, after seeing all these data, really want to taste the wine made from a variety. The funding in the project was not sufficient for winemaking, but we are pleased that Constellation Brands agreed to make wines from them last year and we hope they can again this year. So eventually, we will have wine assessments as well as grape assessments.”
Pointing out that wines are 75 percent from the labeled varietal and the rest from something else, Wolpert said he expects to gain two things from the trials.
First, they can determine what to use in the 25 percent blended portion to bring up the wine character. “But we also think if we can make a better Merlot or Cabernet, those varieties used for blending will be more competitive in the marketplace.”
The field tour also included a look at the rootstock plots of Peter Cousins, USDA-ARS grape rootstock breeder and geneticist stationed at Geneva, N.Y.
Cousins established the trials at KAC to evaluate improved rootstocks in 2005 with cooperation from UC and other USDA scientists.
“Root-knot nematodes infest as much as 65 percent of California's vineyard acreage with statewide losses up to 20 percent of production,” he said.
He went on to say use of today's nematode-resistant rootstocks, such as Harmony and Freedom, apparently selects for aggressive, resistance-breaking nematode populations. At the same time, nematode management options with chemicals are decreasing with the phase-out of methyl bromide and the stricter regulations of other fumigants. What's more, fumigants, while effective at the beginning of a new vineyard's life, decline afterward. That is why improved rootstocks to offer protection over the lifespan of the vineyard are needed.
The process begins with making controlled crosses between parents to seedlings having superior nematode resistance and horticultural characteristics, Cousin explained, adding that the KAC site is ideal for growing rootstocks.
“In order to determine the propagation ability of nematode-resistant rootstock selections, we test cuttings for their ability to produce shoots, roots, and callus from dormant hardwood sections.”
After testing for nematode resistance and propagation, the best selections are grafted and planted for evaluation and comparison with Freedom.
Cousins has tapped various sources, including wild grape species that are native to the Eastern or Southern U.S., along with some from Mexico, that can stand up to root-knot nematodes. These include Vitis mustangensis, V. cordifolia, V. rotundifolia, and others.
The program is constantly releasing finalist selections for virus testing, eliminating others, and accepting new entries. A group of nine finalists planted in 2005 is scheduled to advance to virus testing at Foundation Plant Services this year, and a group of new candidates have been selected for planting.
Beyond resistance to the nematodes, Cousins is selecting from candidates that have resistance to phylloxera and are adapted to abiotic stress, soil conditions, and management practices.
The event also included a visit to the irrigation project headed by Andrew J. McElrone, USDA-ARS plant physiologist at Davis. Situated in a vineyard of 20-year-old Thompson Seedless, the project features a weighing lysimeter installed in 1987 with support from a group of industry organizations.
In describing the equipment's function, one of the collaborators, Larry Williams, UC irrigation specialist at KAC, said it measures water use of a grape vine that is not stressed for water. It is employed with an arbor system to simulate water use of dried-on-the-vine raisins or table grapes.
The lysimeter produces water crop coefficients to validate McElrone's measurements with thermocouple needles to monitor sap flow through the vines for comparison with California Irrigation Management Information System data. Other similar sites are at Davis and Oakville.
“These sensors show excellent potential to measure site-specific crop coefficients and incorporation into real-time irrigation management,” said McElrone.