Viticulture, growing grapevines for wine production, may be mostly confined, in the northern hemisphere at least, to a band between the 30th and 50th parallels, Estonia at 58-59 degrees has more scope than might at first be expected.

For one thing, Estonia's neighbor to the south, Latvia, already has more than one strain of grape which can be used to make relatively light white wines.

The Ministry of Regional Affairs and Agriculture has launched a tender to help breed a wine grape strain suited to Estonia's northerly climate, aiming for a variety that also meets EU regulations on viticulture.

"The selection of parent varieties for a new cultivar depends on many factors: We need winter hardiness, resistance to grape phylloxera and simply a good wine, and we must also take EU legislation into account," said Kadri Karp, professor emeritus of horticulture at the Estonian University of Life Sciences (EMÜ).

The current winter aside, Estonia's winters are often mild, which would mean growers must be prepared for grape phylloxera to arrive here as a new pest. Since 2021, Estonia has belonged to the EU's grape-growing Zone A, the coldest permitted wine-producing regions, primarily located in Northern Europe, as far north as Sweden and including some of the wettest regions, like Ireland – often the rain rather than the cold prevents a good quality wine grape from growing.

In other words, producers must meet similarly strict requirements as such wine-growing heartland nations as France and Germany. Together with colleagues Reelika Rätsep and Mariana Maante-Kuljus, Karp carried out a preparatory study in 2022–2024. The scientists' aim in that study was to map and analyze which existing varieties might provide the desired traits for Estonia's posited future national grape variety, when used in crossbreeding.

"We have been discussing, so to speak, who to choose as the 'parents'," Karp noted.

Delicious, native and pest-resistant

The proposed grape variety must in any case be able to survive winters in which thaws alternate with severe freezes.

"For a variety to be hardy, it is important that the shoots begin to lignify (become woody – ed.) early on. If they lignify too late, they will remain vulnerable to winter damage," Karp explained. A resilience to fluctuating winter conditions like those seen in Estonia can be offered by hybrid varieties developed using hardy American species, for example, the Latvian Zilga variety.

"At the same time, if we make wine from 'Zilga' berries, it will contain American flavor nuances which are not particularly appreciated in Europe," Karp said. "We hope to breed a variety whose bottled wines would agree with the European palate, within the wine world."

In cultivating a new strain, a female "parent" passes on growth characteristics to the offspring, while the male "parent" ensures a wine's quality.

For this reason, the working group found that if Zilga or another Latvian strain, Supaga, were used as the female parent, the French Leon Millot grape would be suitable as the male component. "The grape characteristics of the latter are very similar to the widely known Pinot Noir. Almost every Estonian has probably drunk Pinot Noir wine," Karp said by way of comparison.

In addition to its European-style bouquet, Leon Millot offers another advantage: Greater resistance to grape phylloxera damage in its offspring. In Europe, phylloxera has so far mainly been fought by grafting grapevines, attaching established European varieties such as Pinot Noir or Chardonnay onto phylloxera-resistant American rootstocks.

Although grape phylloxera is not yet found in Estonia, it could arrive within five to 10 years if the winters remain generally mild. "It may happen that by the time we have a completed variety, the pest is already here. We want a plant on its own roots, not a grafted one, because in harsher conditions the canopy may be damaged, and with a self-rooted plant, it is easy to grow a new canopy," Karp explained.

Alongside a European flavor profile, compliance with EU requirements is also important. One of these is that the Vitis vinifera (common grapevine) must be present in a variety's pedigree.

"If the pedigree contains only [North American species] Vitis labrusca and/or Vitis riparia, then that variety may not be grown. Americans can grow it, we cannot," Karp explained.

Second, the law states that in a poor year, when the grapes do not develop enough sugar, a producer may up the alcohol content of their wine by adding sugar, but only to a maximum of 3 percentage points by volume. "The grape itself must have a minimum potential sugar content. This makes breeding more complicated than is the case, for example, with apples," the researcher noted.

May be a matter of decades before an Estonian wine grape becomes a reality

So when might Estonians be able to actually taste their own wine, fermented from the planned new variety? According to Kadri Karp, this is a long way off: At best a couple of decades from now. Sadly, this means even Karp herself may not live to see a genuine, EU-standard Estonian wine.

"It takes a long time, and I may not live to see the new variety myself. Fortunately, our research group spans different age groups and my colleagues will continue the work," she reflected.

The breeding process itself consists of several stages. To start off with, before the flowering starts, the stamens are removed from inside the flowering bud, to prevent self-pollination. Scientists will then transfer the desired pollen onto the stigma of the female plant and cover it with a protective bag, to prevent any foreign pollen from entering. The new type of berries then develops under the bag.

"The grape flower is tiny, so it is delicate work that we do with tweezers and magnifying glasses," Karp explained. They must also ensure that a damp spring will not hinder pollen development.

The working group plans to carry out crossbreeding of this kind over two springs. Each year they wait until autumn, when the seeds of the first berries turn brown. The team then places them in the refrigerator for four months over winter, layered with peat and sand. In spring, the seeds are sown. "From the moment of sowing, it takes three years before we see the first flower, the first berry," Karp described. In the next stage, in the third to fifth year, the team culls some of the plants for the first time.

"As a result of crossbreeding, seedlings may appear whose flowers have curved stamens and whose self-fertilization is hindered. We do not want such varieties in production," Karp explained. Plants that immediately become infected with diseases, for example, downy mildew, are also discarded. By the sixth or seventh year, the vines produce enough yield to organize tastings and small-scale wine-making trials.

From there, the scientists cooperate with the winemakers. Together they decide which seedling to propagate further. Once the selection is made, trials continue in production vineyards. "Selected clones are planted in different locations, both on the island of Muhu and in South Estonia. We must find a variety that retains its good qualities under different conditions and in different soils," the professor noted.

At this stage, another six to seven years will have to pass, to see how the plant reacts when at least 30 individual plants are grown in different places. "If all 30 retain the same characteristics, then the project will have real promise," Karp said.

According to her, there is demand in Estonia for breeding a new variety, as since delicate varieties can be grown in poly-tunnels here, a hardy variety suitable for open fields is what is really needed. "Producers want a variety which can provide a stable yield and, given our region, wine with the right aroma and flavor profile," Karp said.

In Karp's view, wine made from an Estonian variety would in and of itself be a beautiful thing, bringing more diversity and distinctiveness to the wine world.
"When a French person comes to Estonia, they want to be able to taste something new. The variety name is printed prominently on the wine bottle: It could be something beautiful and associated with the North," Karp reflected.

While, so far as Europe goes, viticulture is mainly associated with France, Spain, Portugal, Italy, Bulgaria, southern Germany, and other more southern lands, historically it has been found as far north as southern Scandinavia, a trend which is reappearing in modern times: One of the most northerly functioning vineyards is the Lerkekåsa Vineyard near Oslo, Norway, at 59°45'N, a fraction north of Tallinn, though more influenced by warming Atlantic currents.

Vitis vinifera and other wine grapes are considerably sweeter than the table grapes sold in supermarkets.

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