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Grape Production in New York
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The decision as to whether you will need a special rootstock (rather than own roots) in your vineyard, and which of the resistant rootstocks should be utilized can be very complex. Because it can only be made once in the lifetime of the vineyard, the decision should be carefully and deliberately made. However, even though the decision appears complex, the practical choices for New York growers are few. This is an area of active research, so we hope you will have more and better choices in the future.
The term resistant is important. Rootstock varieties have been bred or selected to provide resistance and/or tolerance to an insect, a soil condition, a disease or an environmental problem. If these conditions are not present, or if the roots of the scion variety itself have sufficient tolerance to the problem, then using grafted stocks will only increase expense and complicate subsequent vine management. On the other hand, using the wrong stock can be a disaster, as the growers in the Napa valley have found when they selected a rootstock with inadequate resistance to phylloxera, A x R #1 (Ganzin 1).
In New York we can expect rootstocks to do one of the following:
1. Provide increased resistance to soil borne pests such as phylloxera or nematodes.
2. Combat replant effects (primarily high initial phylloxera population, but perhaps also impact of nematodes and crown gall bacteria).
3. Provide increased lime (calcium) tolerance.
4. Provide a larger root system to improve vine drought tolerance.
5. Provide cold tolerant roots and trunk.
6. Reduce chance of virus transmission by nematodes.
In other grape production regions additional benefits, such as salt tolerance, may be expected. We are still attempting to locate a source of tolerance to low soil pH for New York grape growers. However, in New York and well as in most of the viticultural world, the overwhelming need is for tolerance of the root aphid, phylloxera. With Native American and French-American hybrid varieties the desired rootstock response in New York is always increased vigor (vine size). Although vinifera varieties have no inherent tolerance of phylloxera feeding, the goal is not always maximum vine size. Active research is underway to investigate the possibility that rootstocks can increase cold tolerance, can resist infection by crown gall bacteria or can control vegetative growth and so improve canopy density and increase cold hardiness. However, these are still theoretical, rather than actually proven, benefits of rootstocks.
In some places in the world, especially in parts of Europe, the soil is almost pure chalk (calcium carbonate) and grapevine roots cannot absorb sufficient iron to provide the vine's needs. Because iron is a key component of chlorophyll, such vines are very yellow (chlorotic). The ability to obtain sufficient iron atoms in the presence of a high concentration of calcium (limestone) is called lime tolerance. As a class, American grape species do not tolerate lime well, but vinifera roots are among the most lime tolerant grape species. Thus the need for lime tolerance was not recognized until after the introduction of phylloxera in Europe when lime intolerant American species replaced the lime tolerant vinifera rootstocks.
Native American (Vitis labruscana) varieties, as a class, are very lime intolerant. For this reason grape production in New York was traditionally restricted to low limestone soils. This means that people wanting to grow Native American (and a few hybrid) varieties on higher pH soils, may be need to use a lime tolerant rootstock. Although most rootstocks used in New York are only considered moderately lime tolerant by the French, their tolerance is sufficient for the more modest limestone content of our New York soils. Of the widely available rootstocks, both 5BB and 5C are noted for good lime tolerance. Both trace their tolerance to V. berlandieri genes. In nature that grape species grows in Texas soils which have very high lime concentrations.
The need for lime tolerance, and for other desirable horticultural characteristics such as ease of propagation has repeatedly caused problems for grape growers. V. vinifera has been crossed with phylloxera resistant species with the aim of combining lime and phylloxera tolerance. Such progeny have found favor in several production areas of the work, but unfortunately, the phylloxera resistance has proven to be too narrow. Vineyard districts which have relied on vinifera hybrid stocks have experience the emergence of resistant phylloxera populations. The last well known example is northern, coastal California where thousands of acres of vines planted to AXR #1 (Ganzin 1) had to be replaced after phylloxera which thrived on AXR #1 roots became established. In Europe rootstocks resulting from crossing with V. vinifera are not allowed, except in a very few regions of almost pure chalk soil, such as Champagne. There vinifera hybrids such as 41B are commonly used.
For more on soil pH and grapevine growth see
The phylloxera resistance of these native and hybrid varieties is variable, but rarely high. Most have sufficient resistance to grow and maintain adequate vine size when the initial phylloxera pressure is not great. However, there is an interaction between vine vigor and pruning or crop level. In New York, the yield potential of most of these varieties will be increased when a more phylloxera resistant rootstock is used.
The figure illustrates the effect of phylloxera resistance on vine size and productivity of non-divided Concord grapevines growing at the Vineyard Laboratory in Fredonia, NY. The long term effect of using C.3309 rootstock was an increase in cane pruning weight by about 1 lb per 8 foot spaced vine, and yield was only increased about 1.5 ton/acre/year. In years of abundant rainfall there has been little yield response to grafting, but in years when vines experience drought stress the response is marked.
The response of French-American hybrid varieties to a phylloxera resistant rootstock is illustrated above. These data are for vines which had been machine hedge pruned and machine (or hand) thinned for several years. Open symbols are vines grafted to C. 3309 and closed are own rooted vines. The points represent different thinning levels. The figure illustrates several important points. First grafting increases vine crop capacity (by increasing vegetative growth). Secondly, response to grafting is more important as crop stress is increased (brought about in this case by reduced thinning level), and thirdly, the benefit may be expressed as larger crop size or as enhaced fruit maturity. Because of competition from other grape producing regions, economic reality requires New York growers of all but the most premium varieties to maximize yield of mature fruit. Thus in the future, the yield payoff for grafting hybrid and American varieties to resistant rootstocks will probably become more important.
Another way roostocks can protect grapevines is to reduce the chance of infection of soil born virus. Most soil born viruses are transmited by nematodes and are called nepovirus. The most important grapevine nepovirus is grapevine fanleaf (GVF). This virus is transmitted by the nematode, Xiphenema index. Special rootstocks which resist both the nematode and the virus which have been produced at the University of California, Davis, California. In France genetic engineers have modified standard rootstocks to resist GVF infection, but these are not yet available for commercial use. Forntunately, the nematode vector for GVF is not present in New York, and the disease has not been a problem to our growers. However, two other related viruses - Tomato Ringspot and Tobacco Ringspot - are endemic in many New York soils. These two viruses present in many of our native and weedy plant species, and the virus can be vectored by the nematode, Xiphenema americanum which is also widely distributed in New York. Work by Dr. Dennis Gonsalves at Cornell's Geneva Plant Pathology department indicates that most commonly used New York phylloxera resistant rootstocks are almost immune from infection by the ringspot virus complex.
Resistant rootstocks have a hypersensitive reaction to the virus. When a nematode injects the virus into root tissue, the affected cells usually die preventing infection. Apparently most Vitis vinifera varieties have a similar reaction. The worst possible case is to graft a hypersensitive scion to a susceptible rootstock. When the rootstock becomes virus infected and the virus moves upward to the graft union, the hypersensitivity causes the death of reactive scion tissue. The result is graft union necrosis and vine death.
At one time is was felt that only a few of the hybrid varieties were ringspot susceptible, but experience has shown that while only a few varieties produce severe leaf symptoms, many are substantially devigorated. Presently we suggest the use of resistant rootstocks for all New York hybrid vineyards to gain security from virus infection and to increase vine capacity.
© Copyright 2000 Robert Pool
