Zilga

Main characteristics

Zilga is an open-pollinated/amateur-bred grape variety of an ultra-early ripening period. It was obtained by the well-known Baltic specialist Pauls Sukatnieks by crossing Smuglianka, Dvietes zila, and Yubileynyi Novgoroda varieties. The period from bud burst to harvest maturity takes 102–108 days, which allows harvesting the grapes in late July or early August under Latvian climatic conditions. The Zilga grape variety demonstrates a high level of adaptation to the cold climate of the Baltic states and has been officially recommended for commercial and home gardening cultivation in Estonia since 2004.

The variety features a stable and high yield by the standards of northern viticulture. The clusters are cylindrical with a distinct wing, dense in structure, and their weight varies from 100 to 400 g. The berries are uniform, slightly oval or round, blue (black) in color, with a well-visible pruin, and their average weight is 4.1–4.3 g. The pulp is mucilaginous, and the taste has a moderately pronounced labrusca (isabella) aroma. The juice is clear and slightly colored. The tasting score of fresh grapes is 7.1 points. The harvest possesses good transportability.

Morphological description

Unfortunately, there is no full detailed description of the morphology of the Zilga variety in academic works. Therefore, the following limited data are provided based on the observations of the amateur winegrowing community:

• Bush: possesses high vigor; shoots develop intensively.
• Leaf: the formed leaf blade is large and acquires a distinct intensive red coloration during the autumn period.
• Annual shoot: cane maturation occurs very early, with high quality along the entire length.

Features of agricultural technology

The number of fruitful shoots on the bush is 80–85%, and the average fruitfulness coefficient equals 1.5–1.9 clusters per shoot. The recommended pruning of fruiting canes is short, leaving 2–4 buds. The total optimal bud load per bush is 30–40 buds. Compatibility with common rootstocks in grafting is good. The variety is suitable for training as an arbor culture.

This grape variety possesses outstanding winter hardiness. Fruit buds withstand winter temperature drops down to -25...-26°C, while the tissues of the cane and perennial parts of the bush can withstand frosts down to -30…-35°C. The Zilga variety is genetically resistant to major fungal diseases: downy mildew, powdery mildew, and gray mold, which is confirmed by long-term observations. The ripe harvest can remain on the bushes for a long time without losing its market qualities, cracking, or decreasing its flavor characteristics.

Winemaking and features of the finished product

The universal variety Zilga is actively used in northern winemaking for the production of red table wines. The technological conditions of the must significantly depend on the climatic factors of a specific year and cultivation region. In Latvia, this variety stably accumulates 18–22% of sugar with a titratable juice acidity within 4.5–5 g/l.

Under the cool climate conditions of Estonia, according to field trials data (2011–2013), sugar accumulation in open ground is limited to 13.5–17.9°Brix, while the juice acidity level remains excessively high (1.4–1.6 g per 100 g of product). When growing the variety in unheated plastic greenhouses, the juice sugar content reaches an optimal 24.1°Brix, and the acidity decreases to 1.2 g per 100 g, which allows obtaining high-quality must. The full phenolic maturity of the berries varies by season: the maximum content of phenolic compounds (293 mg / 100 g) is recorded in dry and warm years, while the accumulation of anthocyanins in the skin accelerates during pronounced fluctuations between day and night temperatures.