Grape Rootstocks for Michigan (E3298)
Michigan vineyards need rootstocks that provide some cold tolerance while also resisting Phylloxera and nematodes. This 8-page bulletin suggests the best standard and experimental options.
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Specifically, it focuses on the use of grape rootstocks to suppress soil pests, control vegetative and reproductive activities of the grapevine with recommendations for Michigan and other areas with similar conditions.
This bulletin focuses on using grape rootstocks to control vegetative and reproductive activities of the grapevine through modifying vine physiology. Several studies have focused on scion and root interactions that have specific regulative mechanisms in key physiological processes for roots in general, for example, water and mineral absorption when they operate under limiting conditions due to drought, pests, disease or other factors (Keller, 2010). However, our knowledge of rootstock physiology is limited as evident in commercial viticulture where 90 percent of all the vinifera vines of the world are still grafted to fewer than 10 rootstocks.
Moreover, rootstocks are chosen mainly for their tolerance to a limited number of expected soil conditions, particularly related to water availability or soil pH (Keller, 2010). Roots anchor the vine to the soil, take-up water and nutrients, produce and transport plant hormones including abscisic acid, auxins, gibberellins, and ethylene (Rom, 1987). Furthermore, roots serve as a repository of stored carbohydrates (Edson et al., 1995) and nitrogenous compounds (Wermelinger, 1991), both critical to fueling the flush of spring growth prior to full canopy expression.
However, the effect of rootstocks on important quantifiable viticultural parameters is ambiguous largely due to our inability to effectively separate the observables with respect to their cause. This, of course, often makes a determination speculative. Additionally, a genotype’s performance is intimately tied to the environment of its evaluation. This relationship can influence the rootstock’s performance, as well as the scion cultivar grafted to it, producing yet another limitation on the validity of any conclusion drawn about the rootstock effect.
No matter how we elect to move forward, determining direct responses to root influences requires an initial defining of two key terms (Striegler and Howell, 1991). A primary rootstock effect would be one that directly influenced a scion response via well documented aspects of root morphology or physiology. A secondary root effect would include an indirect scion response influenced by the rootstock’s direct impact on scion vigor. Canopy density is an example of the secondary root effect.