Unearthing the Secret to Tropical Viticulture: How the IAC 572 Rootstock Powers Skugga Estate

The part of a grapevine that most determines its survival in a tropical climate is the part nobody sees.

Above the soil at Skugga Estate in Mae On, Chiang Mai, the vines carry the genetics of classic European wine grape varieties. Shiraz, with its thick dark skins and spice potential. Pokdum, Thailand's native hybrid, with its tri-species resilience. These are the varieties that will define the character of the wine. But their ability to survive Mae On's heat, humidity, monsoon rainfall, and absence of winter dormancy depends almost entirely on what is grafted beneath them: a specialised rootstock known as IAC 572.

Understanding IAC 572 means understanding why tropical viticulture requires a fundamentally different engineering approach to the vineyard, starting not at the canopy but at the root system buried several metres underground.

Why European Rootstocks Fail in the Tropics

Traditional viticulture operates within a geographic corridor between 30° and 50° latitude in both hemispheres, the classic wine belt where predictable seasonal change provides the biological triggers grapevines evolved to respond to. Cold winters force dormancy. Warm summers drive ripening. The accumulation of heat across the growing season, measured as Growing Degree Days, provides the framework within which sugar and acid develop in proportion.

Mae On sits outside that corridor entirely. There is no freezing winter, no dormancy trigger, and no temperate seasonal rhythm. Vines planted here without adaptation remain in continuous growth, exhausting their carbohydrate reserves, suppressing fruit quality, and becoming progressively more susceptible to the fungal pathogens that thrive in the heat and humidity of the monsoon months.

Planting a classic European Vitis vinifera variety directly into tropical highland soil on its own roots compounds the problem further. The root system itself becomes a liability. Tropical soils harbour microscopic parasitic roundworms called root-knot nematodes that attack vine root systems, disrupting nutrient uptake and stunting growth. Traditional European rootstocks carry no resistance to these pests, historically forcing viticulturists to use broad-spectrum chemical soil fumigants, an intervention that is both ecologically destructive and incompatible with the permaculture farming philosophy at Skugga.

The solution is grafting. The fruiting variety handles what happens above ground. A tropical rootstock handles everything below.

Looking to Brazil: The Genesis of IAC 572

The rootstock used at Skugga Estate was not developed in Europe. It was developed in Brazil, in a research programme established in the 1940s by the Instituto Agronômico de Campinas.

The lead researcher, J.R.A. Santos Neto, recognised early that importing European vines and temperate rootstocks into the humid tropics was biologically flawed. What was needed was not adaptation of European genetics but the systematic development of interspecific hybrids, crosses that incorporated DNA from wild grape species that had actually evolved in tropical environments. The most critical ingredient in that breeding programme was a wild vine called Vitis caribaea.

Vitis caribaea is indigenous to the tropical and subtropical zones of the Americas and the Caribbean. Unlike European wine grapes, it evolved under continuous environmental pressure: relentless heat, intense solar radiation, and year-round fungal pathogen loads that would overwhelm any vine developed in a temperate climate. That evolutionary history produced three properties that the IAC breeding programme needed.

The first is broad-spectrum fungal resistance. In environments where ambient humidity creates near-continuous incubation conditions for fungal spores, traditional vines defoliate rapidly. Vitis caribaea genetics carry innate resistance to downy mildew and powdery mildew, the two most destructive fungal threats in tropical viticulture. The second is metabolic endurance. Continuous year-round growth without a winter rest period is a massive energy drain. Vitis caribaea provides the robust metabolic capacity required for the vine to sustain that workload without physiological collapse. The third is heat tolerance at the cellular level, allowing photosynthesis to continue efficiently under thermal stress that would shut down European vine metabolism.

By crossing Vitis caribaea with established rootstock material, the IAC programme eventually produced the tripartite hybrid designated IAC 572, known colloquially as Jales. It has since become the foundational rootstock for tropical viticulture programmes across Brazil, Thailand, India's Nashik Valley, and other New Latitude wine regions.

How IAC 572 Works Underground at Skugga

At Skugga Estate, European wine grape varieties are grafted onto IAC 572 root systems. The scion, the top half of the plant, produces the fruit. The rootstock, the bottom half, provides the survival infrastructure.

In the loamy clay, partly volcanic soils of Mae On, IAC 572 performs three specific functions that make the vineyard viable.

The first is acid soil adaptation. Mae On's soils are slightly acidic, a characteristic of the volcanic and granitic geology underlying the site. IAC 572 is well adapted to acidic soil environments, establishing expansive root networks aggressively even in conditions where other rootstocks struggle to establish. That root depth and breadth is what allows the scion varieties to access the mineral reserves locked in the granitic bedrock, contributing the savoury, mineral character that distinguishes Mae On fruit.

The second is nematode resistance. IAC 572 carries natural immunity to root-knot nematodes, eliminating the need for chemical soil fumigation entirely. This is not a minor operational detail at Skugga. It is what makes permaculture-based viticulture possible in a tropical soil environment. Preserving the microbial web in the soil, the mycorrhizal fungi, the bacterial populations, the complex subterranean food web that the estate's organic matter baseline sustains, depends on never introducing broad-spectrum soil fumigants. IAC 572's resistance makes that commitment viable.

The third is acidity induction. In hot climates, maintaining natural acidity in the grapes as they ripen is one of the central challenges of viticulture. Malic acid is volatile and is burned away rapidly by the vine's respiration in sustained heat. IAC 572 has been shown to induce significantly greater titratable acidity in the fruit compared to other rootstocks used in similar conditions. Combined with the cool highland nights that Mae On's elevation provides, this acidity retention is what makes balanced, structured tropical wine achievable rather than theoretical.

Managing IAC 572's Vigour

IAC 572's strengths come with a significant management challenge. The rootstock is known for explosive vegetative vigour. In Mae On's fertile, warm, well-watered growing environment, that vigour amplifies further. Left unmanaged, IAC 572 drives rapid shoot elongation and dense canopy development, creating exactly the conditions that harm fruit quality: shaded clusters, trapped humidity, restricted airflow, and the displacement of the vine's metabolic energy away from fruit development and into leaf production.

The response at Skugga is intensive canopy management executed on a continuous cycle through the growing season. Specialised pruning techniques and expansive training systems disperse the rootstock's vigour across the vine's structure rather than allowing it to concentrate in unchecked shoot growth. Competing cover crops between vine rows draw down excess soil moisture, moderating the vegetative response at the root level. The double pruning cycle, described in detail in the estate's account of the Pokdum grape's growing system, provides the seasonal framework within which that canopy management operates.

The vigour that makes IAC 572 indispensable for tropical survival is the same vigour that demands the most skilled viticulture to manage. The rootstock provides the platform. The team's intervention is what makes it productive.

Permaculture Integration Across the Estate

The choice of IAC 572 is inseparable from the broader farming philosophy at Skugga. The estate's permaculture approach prohibits mechanical tilling, avoids synthetic inputs, and designs the vineyard as an integrated ecosystem rather than a monoculture crop.

IAC 572 supports all three commitments. Its nematode resistance removes the most common justification for chemical soil intervention in tropical viticulture. Its deep-rooting behaviour, encouraged by the sloping terrain and contour planting that sheds surface water and draws roots downward, builds the root architecture that makes tilling counterproductive. And its vigour, directed through canopy management rather than suppressed by herbicides or synthetic growth regulators, feeds into the polyculture system where vines, shade-grown coffee, and cacao grow in proximity across the Mae On slope.

That integration is visible across the estate. The same volcanic soil that the IAC 572 root system exploits for mineral depth also supports the cacao programme at Skugga Farm, approximately 1.5 kilometres from the vineyard. The farming principles are consistent across both sites: work with the soil biology, manage water through design rather than drainage infrastructure alone, and build ecosystem resilience rather than optimising a single output in isolation.

Skugga Estate's wine programme is developing as the vines mature. The IAC 572 rootstock was selected specifically for its compatibility with Mae On's soils and climate, and it will underpin every variety the estate grows. To visit the vineyard and learn more about the growing programme, book a tasting experience at Skugga Estate or contact the team at vineyard@skuggalife.com.

Further reading on the estate's wine programme: How the Mae On Climate Shapes Tropical Viticulture, The Pokdum Grape: Thailand's Native Wine Variety, The Soils of Mae On: Decoding Thai Terroir, and Cultivating Shiraz in the Tropical Highlands of Mae On.

Frequently Asked Questions

What is IAC 572 rootstock?

IAC 572, known colloquially as Jales, is a tropical viticulture rootstock developed by the Instituto Agronômico de Campinas in Brazil in the 1940s. It is a complex interspecific hybrid incorporating genetics from Vitis caribaea, a wild vine native to the tropical Americas. IAC 572 provides broad-spectrum fungal resistance, extreme heat tolerance, natural immunity to root-knot nematodes, and the metabolic vigour required for continuous growth in tropical climates without a cold winter dormancy period.

Why does Skugga Estate use IAC 572 rather than a European rootstock?

European rootstocks were developed for temperate growing conditions and carry no resistance to the specific disease pressures and soil pests found in tropical environments. In Mae On's slightly acidic, nematode-present soils, a European rootstock would require chemical soil fumigation to survive and would lack the metabolic capacity for continuous tropical growth. IAC 572 adapts to acidic soils, resists nematodes without chemical intervention, and sustains the vigour needed for year-round growing conditions, all of which are essential for Skugga's permaculture farming approach.

What is grafting and why is it used in tropical viticulture?

Grafting joins two plants: a rootstock, which provides the root system and survival infrastructure, and a scion, which provides the fruiting variety above the graft union. At Skugga Estate, premium European wine grape varieties are grafted onto IAC 572 root systems. The scion produces the fruit with its characteristic flavour and structure. The rootstock provides resistance to soil pests, acid soil adaptation, heat tolerance, and the acidity induction properties that help balance the fruit in a tropical climate.

How does IAC 572 help preserve natural acidity in tropical wine grapes?

In hot climates, malic acid is burned away rapidly by the vine's respiration during the ripening period. IAC 572 has been shown to induce significantly greater titratable acidity in the fruit compared to other rootstocks used in similar conditions, meaning grapes grafted onto IAC 572 retain more of their natural acid structure at harvest. Combined with Mae On's cool highland nights, which slow acid respiration overnight, this property is central to producing balanced, structured wine in a tropical environment.

Is IAC 572 used elsewhere in the world? Yes. IAC 572 was developed in Brazil and is widely used across Brazilian wine regions, particularly in the São Francisco Valley and Rio Grande do Sul. It has been adopted by viticulturists in other tropical and subtropical wine regions including parts of Thailand, India's Nashik Valley, and other New Latitude wine areas where European rootstocks cannot provide adequate resistance to tropical soil conditions and fungal disease pressure.