According to statistics published by the International Organisation of Vine and Wine (OIV), the global vineyard area in 2022—encompassing wine grapes as well as table grapes, raisins, and juice grapes—amounted to approximately 7.3 million hectares.
Although 7.3 million hectares may be difficult to conceptualize, one comparison is illustrative: excluding the Northern Territories, the land area of Hokkaido is roughly 78,400 square kilometres, equivalent to 7.84 million hectares. In other words, the world’s total vineyard area is only slightly smaller than the entire landmass of Hokkaido. Opinions may differ regarding whether this is “large” or “small,” but the fact that a single crop occupies such an expanse is remarkable by any measure.
Across a vineyard area broadly comparable to the size of Hokkaido, a substantial proportion of grapevines—especially wine grapes, which account for roughly 70 percent of global vineyard area—are cultivated using grafting. In wine grape production, the adoption rate is effectively 100 percent. Vines grown without grafting are encountered only in very limited regions under specific conditions.
It is widely known that virtually all wine grapevines are grafted. However, the technical nature of grafting, and the extent of its influence on vine physiology and viticultural outcomes, is not necessarily well understood.
This article focuses on the “rootstock” component of grafted grapevines—an element that has become foundational in modern viticulture.
Grafting and Rootstocks
Grafting refers to the deliberate union of two or more plant tissues to form a single functioning plant. The lower part, which develops into the root system, is termed the “rootstock,” while the upper, fruit-bearing part is the “scion.”
Rootstock–scion combinations may involve different species or the same species. In wine grape production, both components belong to the genus Vitis, yet they differ in species composition.
Grafting can take place at various developmental stages. Viticulturists may graft onto mature vines to convert existing vineyards to new varieties, or they may graft rootstock and scion during nursery propagation before planting. Both approaches are used according to operational needs.
In practice, nursery-supplied wine grape vines are almost always grafted. In many wine-producing countries, planting ungrafted vines (“own-rooted vines”) is legally prohibited because of pest-management regulations. Only a few countries—such as Chile or certain regions of Australia—remain exceptions.
Thus, the use of rootstocks is not merely a convention but a near-universal requirement in global wine grape production.
Why Rootstocks Are Legally Mandated in Grapevine Production
Seed propagation modifies genetic composition through sexual recombination, making it impossible to reproduce a cultivar with identical traits to the parent plant. Consequently, vegetative propagation—grafting or cuttings—is essential for maintaining the genetic identity of cultivated Vitis vinifera varieties.
However, the reason grafting became legally mandated in many wine-growing regions extends far beyond the need for clonal fidelity. The decisive factor was pest control, specifically the threat posed by Phylloxera (Viteus vitifoliae).
Although grafting had long been used in other fruit and horticultural crops, its widespread adoption in viticulture arose only in the mid-to-late nineteenth century.
The turning point was the introduction of Phylloxera from North America to Europe in the 1860s, which caused catastrophic losses in European vineyards.
Phylloxera feeds on both leaves and roots, but its root-feeding habit proved fatal to European grape varieties (Vitis vinifera). The only effective, durable countermeasure was grafting: viticulturists used American Vitis species—such as Vitis riparia and Vitis rupestris, which demonstrated natural tolerance to Phylloxera—as rootstocks, and grafted traditional European cultivars onto them. This strategy, adopted in the 1880s, enabled the gradual restoration of European viticulture.
As Phylloxera spread globally, rootstock use became the practical—and eventually legal—requirement in most wine-producing regions. Only a handful of areas where Phylloxera has never been detected remain exceptions.
Three American Species Form the Basis of Modern Rootstocks
The primary requirement for a grapevine rootstock is resistance to Phylloxera. To date, Vitis vinifera cultivars lack sufficient resistance, whereas certain American species—including Vitis riparia, Vitis rupestris, and Vitis berlandieri—exhibit functional tolerance.
Thus, nearly all rootstocks used in viticulture descend from American Vitis species. When Vitis vinifera genetics appear in a rootstock, it is always as part of a hybrid rather than a pure species.
Although numerous Vitis vinifera cultivars exist—Riesling, Pinot Noir, Chardonnay, Cabernet Sauvignon, Syrah, among many others—the genetic basis of rootstocks is surprisingly narrow.
Despite the abundance of named commercial rootstocks, most are hybrids derived from just three species: Vitis riparia, Vitis rupestris, and Vitis berlandieri.
Characteristics of Pure-Species Rootstocks
While the majority of commercial rootstocks are hybrids, the three key American parent species each possess distinctive ecological and viticultural traits.
Vitis riparia is native to riverbanks and low-lying, moist soils, and it typically develops shallow root systems characteristic of such environments.
Vitis rupestris, in contrast, grows in rocky, nutrient-poor slopes, producing deep, penetrating roots and demonstrating strong drought tolerance. It also adapts well to sandy soils. Both species have been used directly as pure-species rootstocks, such as Riparia Gloire de Montpellier and Rupestris du Lot.
Vitis berlandieri originates from calcareous soils and exhibits high lime tolerance and adaptation to alkaline conditions. It also shows strong drought resilience.
However, because V. berlandieri roots poorly from hardwood cuttings, it is rarely used as a pure-species rootstock; instead, it contributes to hybrid combinations through breeding.
Parentage and Hybridization in Rootstock Development
Except for a few pure-species examples, nearly all commercially relevant rootstocks result from hybridization among the above species. Some hybrids even include Vitis vinifera parentage, though this is uncommon.
Hybrid rootstocks inherit traits from their parents, but inheritance patterns are neither uniform nor predictable. Even sibling vines from the same cross may exhibit substantial differences in root depth, drought tolerance, lime tolerance, vigor expression, and overall nutrient uptake capacity.
For this reason, multiple distinct commercial rootstocks may originate from the same parental cross.
For example, the rootstocks 5BB and SO4 share the same parental combination—Vitis riparia × Vitis berlandieri. Yet they express different balances of inherited traits and are classified as separate cultivars.
Both display lime tolerance due to V. berlandieri parentage, but they diverge in vigor, drought tolerance, canopy expression, and yield potential.
5BB was developed by Hungarian breeder Sigmund Teleki and is considered one of the three major Teleki rootstocks. It is known for strong drought tolerance and early maturation. Another Teleki-type rootstock, 5C, also arises from a riparia × berlandieri cross but exhibits lower drought tolerance and better winter hardiness, leading to its widespread adoption in regions such as Hokkaido. Teleki types tend to develop relatively shallow root systems.
SO4 (Selection Oppenheim 4) is one of the world’s most widely used rootstocks. Like the Teleki types, it originates from a riparia × berlandieri cross, but it is characterized by vigorous growth and high yield potential. Its drought and lime tolerance make it adaptable across many wine regions, though it generally performs best in relatively fertile soils.
Implications of Root System Differences
Given that grafting was introduced to replace Vitis vinifera roots—which lack Phylloxera resistance—with tolerant American roots, it is self-evident that rootstock selection determines the structural and functional characteristics of the vine’s root system.
Because nearly all water and mineral nutrients enter the plant through the roots, substituting the root system with one from a different species is a substantial physiological modification. In practice, different rootstocks impart measurable differences in water and nutrient uptake.
Variations in water-uptake capacity manifest visibly as differences in vegetative growth rate and vigor. Rootstocks with strong uptake capacity generally provide more stable water supply under drought stress, reducing physiological limitations on photosynthesis. Since water stress suppresses photosynthetic activity, rootstock-mediated drought tolerance can indirectly influence vine growth and fruit composition.
Root system size and architecture also affect the accumulation of storage reserves, which influence vine productivity and flower-cluster initiation. Accordingly, differences in rootstock performance may translate into differences in yield potential.
This topic is discussed further in another article addressing vine age, productivity, and wine quality.
Root systems also modulate the production, transport, and accumulation of plant hormones involved in growth regulation and environmental response. Substituting rootstocks therefore has the potential to alter hormonal dynamics within the vine.
Studies have shown that certain hormonal effects influence vigor, stomatal behaviour, and yield expression. However, relative to the effects of scion cultivar differences, environmental conditions, and year-to-year climatic variation, rootstock-driven hormonal effects are considered comparatively modest.
The extent to which rootstock differences translate directly into perceptible sensory differences in finished wine remains an open scientific question.
Rootstocks as Tools Against Pests Beyond Phylloxera
Whether rootstocks will remain a permanent safeguard against Phylloxera is not definitively known, but the grafting-based solution itself is regarded as mature and effective. Contemporary breeding efforts focus instead on rootstock-mediated resistance to other soilborne pests, most notably plant-parasitic nematodes (phylum Nematoda).
Plant-parasitic nematodes damage vines by penetrating roots with needle-like stylets and extracting nutrients. At high population densities, nutrient extraction can lead to reduced growth, decline, and eventual vine death. Moreover, nematodes act as vectors for certain pathogenic fungi and viruses, enabling rapid disease spread once symptoms appear.
Although nematode damage resembles Phylloxera damage in that both originate in the roots, Phylloxera-resistant rootstocks do not necessarily confer nematode resistance.
Hence, contemporary rootstock breeding programmes aim to incorporate nematode resistance, making pest tolerance—beyond Phylloxera—a major modern focus.
Rootstocks Do Not Directly Determine Wine Quality
The question of whether rootstocks influence wine quality has been studied extensively. The prevailing view today is that rootstocks do exert influence, but largely indirectly, and the magnitude of direct chemical or sensory effects is generally small. Some researchers interpret the effect as negligible in practical terms.
Fruit quality is fundamentally determined by the scion cultivar, layered with seasonal climatic conditions (vintage) and viticultural practices.
Rootstocks influence vine performance indirectly—through soil adaptation, water-uptake capacity, vigor regulation, canopy architecture, and cluster morphology. These secondary effects may subsequently influence grape composition, but the rootstock does not directly alter must chemistry per se.
Controlled experiments in which identical scions are grafted onto multiple rootstocks, grown under uniform conditions, and vinified equivalently have demonstrated measurable differences in pruning weight (a proxy for vine vigor).
However, numerous studies report no significant differences among rootstocks in major chemical metrics such as must sugar concentration or titratable acidity.
Further discussion of root-system differences and own-rooted cultivation appears in a separate article.
Synthesizing current evidence, rootstock selection is better understood not as a tool to provide additional quality advantages, but rather as a mechanism for avoiding potential disadvantages by matching the vine to its environment.
With ongoing climate change, rootstock breeding now increasingly targets tolerance to heat, drought, and extreme weather. The concept of “selecting the appropriate rootstock to avoid latent disadvantages” is expected to become even more important in future viticulture.
