How Do Sauvignon Blanc Clones Differ?
Trial plantings in Mendocino begin to yield data and tasting results
Kelseyville, Calif. -- Sauvignon Blanc vineyards planted in California are perhaps the least diverse in terms of clonal selections in use among the major grape varieties. Even though the number of registered Sauvignon Blanc clones has increased to 22 selections at the University of California-Davis’ Foundation Plant Services (FPS) during the past decade, an estimated 98% of all Sauvignon Blanc planted in California is the Wente clone FPS 01.
With the growth in popularity of Sauvignon Blanc, and its diversity in styles and consumer preferences, growers and winemakers want more information on these clones and their potential contributions in producing the variety. Given the importance of Sauvignon Blanc as the signature white varietal of Lake County, the Lake County Winegrape Commission in conjunction with the University of California Cooperative Extension hosted a meeting this week to hear a progress report on a Sauvignon Blanc trial evaluating 12 FPS clones. In addition, Lake County growers and vintners were given the opportunity to taste and compare the first wines produced from the trial from the 2008 vintage.
Glenn McGourty, UC Cooperative Extension winegrowing and plant science advisor for Mendocino and Lake Counties, is conducting the clonal field trial in Mendocino County in cooperation with Fetzer Vineyards at a vineyard in Hopland. The research project began with vine planting in 2004 and is being funded by the American Vineyard Foundation and the Viticulture Consortium West. McGourty said the overall goal of the trial is to examine how different clones may be used to improve yield and quality in Sauvignon Blanc.
The clonal lineup
Nancy Sweet with Foundation Plant Services at UC Davis provided the following background about each clone in the trial, and noted that about half have only been registered and available from FPS since 2001.
• FPS 01, the Wente clone, was planted in the Livermore area in the 1880s, but it originally came from Chateau d' Yquem in Bordeaux, France.
• FPS 06, 07 and 17 are all Italian selections from the viticulture institute in Conegliano, Italy.
• FPS 14, 18, 20 and 25 are all French selections from Bordeaux, and Sweet said 14 is one of the most popular Sauvignon Blanc clones in France.
• FPS 22 is a California selection from an old, head-trained vine found at the UCD Oakville Experimental Research Station, and it entered the FPS collection in 1990.
• FPS 23 came from a Kendall-Jackson vineyard on Howell Mountain, Napa County, planted in the 1980s, but is believed to have been previously planted in the Russian River area in Sonoma County.
• FPS 26 is the Napa Heritage clone from a vineyard in the Oakville area planted around 1945.
• FPS 27 is the Musque clone that came from Bordeaux, France, in 1962 and was originally labeled “Savagnin musque.” It is probably the second most planted clone in California, but may only total 1% or 2% of Sauvignon Blanc acreage. Musque was popularized by Ventana Vineyards’ Doug Meador, who discovered in field trials during the 1970s that it did not show excess vegetal character in the cooler Monterey County climate. (More information on all available clones can be found on the National Grape Registry website at ngr.ucdavis.edu http://www.ngr.ucdavis.edu/.
Viticultural data
The 12 clones were planted in 2004 on 101-14 rootstock on a VSP trellis system with spacing of 8 feet by 7 feet. The clonal trial is tracking and comparing overall yields by clone, cluster numbers per vine, cluster sizes and weights, berry weights, pruning weights, and Brix, pH, and TA levels at harvest. McGourty believes a clonal trial should last at least 10 years, and should produce at least five years of viticultural data. Harvest and viticultural data has been gathered since 2007, when the young vines had low yields. In 2008, spring frost reduced yields, so McGourty said 2009 is probably the first year with good yield data.
Data to date show clones 01, 06, 18, 23 and 25 generally produce larger clusters and higher yields of around 6 tons per acre. Clones 07, 14 and 17 tend to produce smaller clusters and yields of around 4 tons/acre. McGourty noted that larger clusters could work in many parts of California because they will ripen early enough, but in cooler climates, smaller clusters may be preferred. Overall yields have ranged from about 4 to 6 tons per acre, but that could increase as vines mature. In some California locations, including Lake County, up to 8 tons per acre can ripen and provide a good balance of yield with quality. At harvest 2008, pH values were higher than expected, ranging from about 3.6 to 3.8, but in 2009, each clone came in lower, in a desirable range from about 3.2 to 3.4.
A trellis trial is also being conducted in rows adjacent to the clonal trial with five different trellis types:
• Vertical shoot positioned (VSP) with bilateral cordon.
• VSP, four canes with two pairs stacked on fruiting wires.
• VSP, bilateral cordon, “flop”, (a modified California sprawl).
• VSP with modified cane pruning to provide a continuous fruit curtain.
• VSP with four parallel canes.
McGourty said the goals of the trellis study are to determine what systems are best to maximize yields, achieve uniform ripeness, produce high quality fruit and be suitable for mechanized harvest. The four cane systems are able to set higher crops and have provided the highest yields, with up to double the number of buds compared with spur cordon systems. Vines with fewer buds generally have smaller but riper crops.
The stacked cane systems, which are used by some growers in Lake County, ripen fruit unevenly with different Brix, pH and TA levels between the top and bottom canes. This system gives winemakers the option to obtain a range of flavors, ripeness, and varietal character in one pick. The parallel cane systems ripened more evenly.
Similarities in taste
The comparison tasting of the 12 clonal wines made from the 2008 vintage was somewhat inconclusive, and it can be partly attributed to the young vines and the inherent problems with small lot winemaking. The general consensus was that the 12 wines shared more similarities than differences. Acidity, fruitiness, body and color were pretty similar throughout. Some tasters indicated a preference for clone 01 and Musque clone 27, perhaps because they are familiar with their clonal character; but clones 25 and 26 also had favorable comments. Wines made in future years from the trial may provide more noticeable differences as the vines mature.
One issue discussed at the meeting is that Sauvignon Blanc character and quality can be very dependent on growing site and management factors. Growers have the ability to influence aroma and flavor characteristics including fruitiness, “vegetal” and green pyrazine characters, and acidity based on trellis type and canopy management, leaf pulling, cluster sun exposure, crop levels, irrigation and picking ripeness. Likewise, winemakers can manipulate aroma and flavor with yeast selection and blending of fruit from different vineyards.
McGourty said, “Clonal selection involves fine tuning a vineyard to a particular situation. Sauvignon Blanc has a lot of things going for it in terms of being able to manage its style depending on ripeness levels, trellis type and other factors, and perhaps clonal differences may not be as important as they are for other varieties.”
But looking to the future, McGourty explained, “What we're doing today with this trial is for the next generation of wine producers. The younger people in the business today will probably get a chance to replant a vineyard during their career, and then they will be able to use this data and information when the time comes.”
