Wine Grape Rootstocks
Rootstocks commonly used are Vitis species selected from native areas or hybrids that use native species to form new rootstocks. When two species are crossed, they normally exhibit characteristics of both species. Some of the most common are Vitis rupestris, V. riparia, V. berlandieri, V. champinii, and V. vinifera. An understanding of the native environment of these species can give clues to their potential adaptation to other areas. A grafted vine consists of two parts, the scion variety (e.g., Pinot Noir), which produces the aboveground parts (trunk, shoots, and fruit), and the rootstock variety (e.g., Paulsen 1103), which provides the root system and lower part of the trunk (See Figure 3.1). The position on the trunk where the scion and rootstock are joined by grafting grows together is called the graft union.
North American Species
The North American species commonly used for grafting grapevines are Vitis rupestris, V. riparia, V. berlandieri, and V. champinii.
V. rupestris roots deeply, has a long growing season with vigorous growth, so it has often been selected for use in warmer, long season regions.
Vitis berlandieri is a vigorous climbing vine with strong, fleshy plunging roots. It is very drought tolerant and can also tolerate very low winter temperatures.
Vitis riparia prefers cool, naturally fertile, deep soils, well supplied with water. It does not do well in calcareous or drought prone soils since the roots grow laterally.
Vitis champinii is a natural cross between V. candicans and V. rupestris. It has been used directly as a rootstock (Dog Ridge and Ramsey) and as a parent in Harmony and Freedom.
North American Hybrids
Since the Vitis species described above often had desirable and undesirable characteristics, cross-breeding was implemented in an attempt to combine the desirable traits. Of the many hybrids (breeding 2 or more varieties) attempted, most of the better results as described came from some specific crosses.
V. riparia X V. rupestris
Rootstocks derived from these crosses prefer deep, fertile and moist soils. These rootstocks offer low-moderate vigor to the scion and in certain situations hasten ripening.
V. berlandieri X V. riparia
These rootstocks offer moderate-high vigor to the scion depending on the soil type. However, rootstocks in this group are more vigorous than those from V. rparia X rupestris crosses especially under available precipitation.
V. berlandieri X V. rupestris
These rootstocks offer moderate-high vigor to the scion, are drought tolerant, and best adapted to warm to hot regions. These rootstocks are suited to a wide range of soil types of low to moderate depth and fertility.
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