Growing & Winemaking

 

Foundation for a Quality Vineyard

July 2009
 
by Glenn T. McGourty
 
 
Goldeneye
 
A marker on the end of this vineyard row at Goldeneye winery in the Anderson Valley signifies that Pinot Noir clone 777 is budded to 420A rootstock, which is a cross of Vitis berlandieri and V. riparia. Most of the modern vineyards in California use hybrid rootstocks such as 420A.
 
    HIGHLIGHTS
     

     
  • Choose rootstock wisely. Once planted, grapegrowers hope to be living with their choices for a long time.
     
  • Rootstocks of the last generation, AXR-1 and St. George, have many favorable attributes, yet St. George is limited to certain varieties and AXR-1 has a famously fatal flaw.
     
  • The author discusses the strengths and weaknesses of many of the most common rootstocks today, which are up to 140 years old.
     
  • Authorities including Dr. Andrew Walker of UC Davis say it makes sense for growers of the future to choose rootstocks that can thrive without much--if any--irrigation.
Rootstocks are analogous to the foundation and basement under a building--they provide support and stability, the utilities enter there, and it is also a place to store things. Most of the time neither is particularly visible or lauded, but both are extremely important to the wellbeing and longevity of their respective tops.

When designing a vineyard, choosing the variety to plant is probably the first thing you will think about. One of the fundamental decisions you will live with for the life of the vineyard is the rootstock that the variety will be planted on. Often this doesn't get the thoughtfulness that it truly deserves. "Out of sight, out of mind" usually reigns, since most of the time (if the rootstock behaves itself well) it is pretty much ignored by the grower.

Besides, there are few physical manipulations that you can make to something as well buried as the average grapevine root system. Water and fertilizer are the only tools we have to invigorate the roots, along with a few nematicides. Competitive cover crops and changing trellises to allow for more buds are the options to devigorate vines. So choose wisely, because once planted, you will be living with your choice for (hopefully) a long time.

In California, we are currently the first generation of winegrowers that has had to embrace some diversity in rootstock choices. The rootstocks Rupestris du Lot St. George and AXR-1 so dominated California vineyards for most of the 20th century that surprisingly little else was considered during that time period, until AXR-1 began to succumb to phylloxera in the 1980s.

When there was no choice

Dr. Michel Salgues, retired former winemaker at Roederer Estate U.S. in Anderson Valley, remembers planning the 300-acre estate vineyard planted in the early 1980s. Budded mostly on AXR-1, the vineyard ultimately began to fail by the mid-1990s due to phylloxera.

"You would think that being from France, we should have known better. Well, we tried to plant other rootstocks, but in the early 1980s all we could find was enough 3309 C to plant 10 acres. We knew that St. George was a bad choice for Pinot Noir or Chardonnay. Besides AXR-1, there was virtually no other type of rootstock available. It would have delayed our project by several years if we had to wait for the nurseries to grow enough nursery material to provide an alternative. And even then, we had no information how different rootstocks might perform under California conditions."

Both AXR-1 and St. George had many favorable attributes--easy to propagate, compatible with many varieties, tolerant of many scions (the top part of the vine) and viruses, and good vigor. AXR-1 had a fatal flaw of being susceptible to phylloxera, and by 1992, the nursery industry stopped propagating it based on the recommendations of University of California scientists and extension advisors alarmed by the sheer number of acres that were succumbing to this devastating little pest.

St. George has poor nematode resistance in replant situations, and has a tendency to cause shatter when used with some varieties (such as Pinot Noir), which limits its use. However, in the North Coast there are still many growers who think this rootstock is ideal for old time favorites Zinfandel and Petite Sirah.

"My old Grandpa taught me one good thing--St. George rootstock is just right for our conditions in Redwood Valley," said Charlie Barra of Mendocino. "We started planting it in the 1920s on our family's place, and again when I started planting premium varieties in the '50s. My vineyards planted to St. George survived, while my neighbors' on AXR-1 needed replanting."

Old World wisdom

Not surprisingly, we turned to our European colleagues for ideas of what we should use when AXR-1 failed. After some initial snickering from the French, who as early as 1963 had sternly warned UC scientists not to use AXR-1, their plant material and experiences were widely shared.

A fundamental difference between Europe and California is that lime tolerance is very critical to many vineyards in Europe, since so much of their terrain is formed from uplifted marine sediment parent material. In California, this is much less of a factor (other than the Paso Robles region and a few other spots).

Glenn Proctor
 
UC Foundation Plant Services uses mother plants for its certification program.
PHOTO:University of California/ Agriculture and Natural Resources
Also, European climates typically have some precipitation during the growing season. In northern European vineyards, it rains regularly almost every month of the year. In southern European vineyards, drought tolerance is important, since growers can't irrigate in most appellations; but a drought in Northern France is quite different than one in the Central Valley of California, since the French can expect precipitation in their vineyards most months during the growing season.

So we began selecting through a catalog of very old plant material, since many of the most common rootstocks were hybridized in Europe following the horrible decimation of the industry nearly 140 years ago by phylloxera. The hybrids were made from a surprisingly small number of Vitis (grape) species imported from the United States.

Vitis riparia is found growing along creeks and streams, and it is not very drought tolerant. It is a good choice for humid soils. Vitis rupestris is very drought tolerant, but doesn't have good lime tolerance. Vitis berlandieri is native to the Texas plains, and while difficult to propagate, it offers the traits of lime and drought resistance when used as a parent with other crosses.

While other Vitis species have been used in rootstock breeding programs, these three were the most important. Hybrids made from them include most of the rootstocks that modern vineyards in California are currently being propagated on, including SO4, 5BB, 5C, 420A (Vitis berlandieri x V. riparia); 99R, 110R, 140Ru, 1103P (V. berlandieri x V. rupestris) and 3309C, 101-14 and Schwarzman (V. riparia x V. rupestris). As a group, they have the weakness of being easily damaged by many plant parasitic nematode species.

The crosses that were made with the European winegrape Vitis vinifera almost always failed to be resistant to phylloxera. With a few exceptions, that is fairly true to this day. To be on the safe side, I always recommend that growers avoid using any rootstock that has V. vinifera in its parentage. The old adage applies, "There are two types of V. vinifera hybrid rootstocks. The ones that have failed, and the ones that are going to."

Nursery trends

Every year is slightly different in which rootstocks are the most widely propagated, since different regions require different materials. Planting cycles change by region, and few years are similar. In many high-quality winegrowing districts, the trend in general is for more compact vines, since many vineyards are being planted at closer spacing.

Allen Holstein, a seasoned viticulturist in Oregon's Willamette Valley, finds that Riparia gloire has a place in the fertile humid soils of the Dundee Hills. "In our close-spaced Pinot Noir vineyards, we find that we can get almost an extra foot of shoot growth at bloom compared to older vineyards with wider spacing. This lets us pick ripe fruit almost a week earlier in October, which can be very critical some years. Riparia gloire rootstock works in our area due to its limited vigor and earliness." Many vineyards have drip irrigation, which is needed some years despite the wet weather for which Oregon is famous. However, outside of Oregon, Riparia gloire is rarely planted.

Rootstock Suppliers
COMPANY PHONE WEBSITE
California Grapevine
 Nursery Inc.
(800) 344-5688 californiagrapevine.com
Concord
Nurseries Inc.
(800) 223-2211 concordnurseries.com
Davis Viticultural
Research
(618) 946-3517 davisvines.com
Double A
Vineyards Inc.
(716) 672-8493 doubleavineyards.com
Grafted
Grapevine Nursery
(315) 462-3288 graftedgrapevines.com
Kendall-Jackson Nursery (707) 836-2021 kj.com
Mercier Grapevines
LLC
(707) 446-9223 mercier-california.com
Mori Vines Inc. (905) 468-0822 morivines.com
NorthEastern
Vine Supply
(802) 287-9311 nevinesupply.com
NovaVine Inc. (707) 539-5768 novavine.com
Sunridge Nurseries (661) 363-8463 sunridgenurseries.com
Vintage Nurseries (661) 758-4777 vintagenurseries.com
For more on rootstock suppliers, see Wines & Vines' 2009 Buyer's
Guide in print or online at winesandvinesdirectory.com

The preferred rootstock in many Californian coastal vineyards planted on deep soils is 101-14 Mgt, and it probably is the most-requested rootstock in grapevine nurseries this year. This rootstock also helps the scion propagated on it to bloom and ripen somewhat earlier than other combinations.

There is some concern about its phylloxera resistance. Dr. Jeffrey Granett, professor of entomology from UC Davis, sampled 101-14 roots for phylloxera feeding from the 1980s through his recent retirement. "When we first sampled, we rarely saw any phylloxera feeding on 101-14 roots. As time went on, we saw phylloxera feeding on small roots, causing nodosities (root tip swelling), but we have never seen tuberosities (lesions of dead tissue on the woody portion of the roots). We see phylloxera feeding in low numbers on many "resistant" rootstocks, but we have concluded so far that this does little long-term damage to the vines. This feeding has also been observed on 5C in Germany. Combined with drought, though, the vines will fare poorly, but we don't think that 5C has actually failed due to phylloxera."

Granett added, "Drought and large populations of phylloxera could be a problem in some vineyards on 5C and 101-14, especially if growers use regulated deficit irrigation (RDI) strategies, or have limited water to irrigate with some seasons."

SO4, another lower vigor rootstock, is among the most propagated rootstocks this year. It is a bit more vigorous than 101-14 Mgt, and it is compatible with most scion material. Closely related 5C has dropped from favor, due to lack of drought tolerance and other abnormalities. However, it has performed well in sites with deep soils and plentiful irrigation.

Due to its lack of vigor and tendency to delay bloom and ripening, 420A has limited appeal. It remains popular in Europe for closely spaced vigorous vines, such as Nebbiolo in Piedmont and Sangiovese in Tuscany, but it is not widely used in California.

Intermediate vigor rootstocks that are less commonly propagated include 3309C and 5BB. 3309C can have difficulties with latent viruses in the scion, so it is essential to use only certified virus-free material. 5BB is prone to Phytophthora root on poorly drained sites, but it performs well in hillside locations where some vigor is needed.

In the category of vigorous rootstocks, 110R and 1103P remain the top choices; 1103P is growing in popularity as both the nursery trade and winegrowers become familiar with this rootstock. It has good lime tolerance--a plus for places like Paso Robles, which has large amounts of limestone under its topsoil. 140Ru has special use as a replant rootstock. Its high vigor allows growers to replace a missing vine without having to worry about supplemental irrigation, if planted as a dormant benchgraft vine.

Finally, 039-16 has special use as a rootstock when fan leaf virus is present in a vineyard along with the vector nematode Xiphinema index. It is a hybrid of Vitus sp. and Muscandinia rotundifolia sp. It is difficult to propagate, and may also affect wine flavors, so it isn't the ultimate solution to minimizing the effects of fan leaf, but it will work.

Future trends

Alternative text
 
A winegrower employs a chip-budding technique on rootstock in the vineyard.
PHOTO:University of California/Agriculture and Natural Resources
Rootstock breeder and viticulture professor Dr. Andrew Walker of UC Davis has spent most of his career breeding new rootstocks with a broad mix of Vitis species that include the old standards plus V. rufotomentosa, V. champinii, V. candicans and V. monticola. Walker believes nematodes are very challenging as we plant vineyards for the third and fourth times on the same land, or grow vines in sandy loam soils previously used by other agricultural crops (especially in the San Joaquin Valley).

UC Foundation Plant Services has released five new rootstocks from nearly 5,000 seedlings that were screened by Dr. Walker and his lab during the past 15 years. The rootstocks are named GRN-1 through GRN-5 ( GRN stands for Grape Rootstocks for Nematode resistance), and are planted now in increase blocks so they should be available in limited quantities for nurseries to propagate in the 2010 season.

These rootstocks are very resistant to dagger nematodes, root knot nematodes, ring nematodes and lesion nematodes. Tests are under way to determine if any are resistant to fan leaf disease. The rootstocks are also very resistant to Pierce's disease. "We are really excited to get to this point," Walker explained, "because these rootstocks represent new genetics with great nematode resistance, which long-term is a big problem for vineyards, especially in replant situations. They are designed especially for where people don't want to use fumigants or wait for long fallow periods between plantings. We don't know very much about these rootstocks agronomically, although we expect them to be drought-resistant and probably salt tolerant as well."

And what does Dr. Walker think about the future of irrigated viticulture? "It probably isn't sustainable with the projected changes in climate, the growth of urban areas, and political pressure to use water for other purposes. It makes sense for us to choose rootstocks that can do well without much additional water. Dry-land farming is of course very sustainable, if you can make the vines grow enough to support an economically viable crop." Seed for thought and a topic of a future column.

When choosing a rootstock
 

 
There are myriad considerations when you decide to plant a vineyard:

The potential vigor of vines grown on the site: Do you need to encourage or discourage vigor?

Compatibility with scion material: Some rootstocks just don't propagate and perform well with certain varieties. (Usually the nursery that you are purchasing your plants from will know about this).

Scion health issues: Is there a potential for latent viruses that might express themselves in some rootstocks but not others? (It is always best to avoid any virus-infected scion material if at all possible, since we are now finding that many viruses are being moved around by vectors such as mealybug.)

Drought tolerance: This is an increasingly important issue, since irrigation water availability and priority for users in an increasingly urban California, where water supply is fed by streams and rivers in which endangered fish species live, is in a state of flux.

Soil-borne pests: Phylloxera are assumed to be everywhere. Nematodes may also be a real consideration in some sites, especially in replant situations. It is a good idea to assess nematode populations before replanting, to see if the ground should be rested and planted to other crops, or treated with a chemical fumigant.

It pays to research and answer these questions, and when the proper rootstock is selected, take the time to have your vines grown for you if they are not readily available.

G.M.

Glenn T. McGourty is the winegrowing and plant science advisor with the University of California Cooperative Extension, Mendocino and Lake counties, and grows his own grapes in Ukiah, Calif. To comment on this article, e-mail edit@winesandvines.com.
 
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