Irsai Oliver

Main Characteristics

The grape variety Irsai Oliver was bred by the Hungarian breeder Pal Kocsis in 1930 in the city of Kecskemet by crossing the parental pair Pozsoni feher (Bratislavskii belyi) × Zhemchug Saba. According to its cluster structure and technological purpose, it is classified as a table-wine grape variety, representing a very high value for winemaking. The vegetative period from the beginning of budburst to the onset of harvest maturity of the berries under the conditions of southern Ukraine is 116 days, requiring a sum of active temperatures at the level of 2250 °C. The variety is very early, with the ripening of the berries occurring at the end of the second decade of August. The vines are characterized by medium vigor with good maturity of one-year-old shoots (about 80%). The grape variety Irsai Oliver belongs to the group of cultures with a stable yield, which on non-irrigated plots averages about 80 centners per hectare.

Clusters of this variety are of medium size (length 11–16 cm, width 9–11 cm), conical in shape, often branched, and are characterized by medium density or a loose structure. The average bunch weight is within 135–140 g. Rounded berries of medium size (length 16 mm, width 15 mm) have an attractive light golden color. The berry skin is dense and durable, the pulp is distinguished by a juicy texture, and the flavor is harmonious with a highly pronounced, very strong citron-muscat tone. The average weight of 100 berries is 290 g. Two small seeds develop inside each berry. The sensory evaluation score of fresh grapes is about 8 points. The product stands out for its intensive sugar accumulation, reaching 21.3–23.3 g/100 ml with a titratable acidity of the juice of 4.5–5.9 g/l.

Morphological Description of the Grape Variety Irsai Oliver

• Young shoot (tip): The tip of the young shoot has a grayish-green color with pink spots and is distinguished by weak pubescence.
• Young leaves: At the initial stages, the leaf blades have a golden color and weak araneose pubescence. Subsequent leaves become light green and completely smooth (glabrous). A low density of foliage on the shoots is noted.
• One-year-old mature shoot: It is characterized by a brown color, while the nodes are visually almost indistinguishable.
• Formed leaf: Leaves are medium in size, rounded, and have a 5-lobed structure with a medium degree of lobing. The central lobe is spirally curved and forms a right or obtuse angle. The leaf blade as a whole is folded in a funnel shape. Pubescence on the lower side of the formed leaf is weak and bristly.
• Leaf incisions and sinuses: Upper sinuses are of medium depth, closed, with an elliptical or egg-shaped opening (rarely open, lyre-shaped). Lower sinuses are small, open, in the form of an incoming angle or lyre-shaped with almost parallel sides. The petiole sinus is open and vault-shaped. Long, light green leaf petioles and tendrils are noted.
• Teeth: The teeth at the ends of the lobes are triangular, with weakly convex sides. The marginal teeth along the edge of the leaf blade are also triangular.
• Saplings: They form semi-spreading bushes with low foliage density on the shoots. Their leaves are 3-lobed, shallowly lobed, with a blunt and spirally curved central lobe. The tendrils are long, thick, and slightly twisted. The autumn color of the leaves turns yellow.

Agrotechnical Features

The grape variety Irsai Oliver is recommended to be planted on well-heated slopes, which guarantees timely ripening and maximum sugar accumulation. Under the conditions of southern viticulture, a stemless fan 4-arm training system is successfully applied. The bud load per bush is set within 40–48 buds, and the recommended pruning length for fruit canes is long, at 8–10 buds (depending on the actual survival of the buds after the winter period). In the most heat-provided areas on southern and southwestern slopes, it is possible to conduct a high-stem training system. Riparia × Rupestris 101-14, Berlandieri × Riparia SO4, Kober 5 BB, and Teleki 85 act as recommended rootstocks. The variety responds sharply to a lack of moisture, demonstrating a sharp drop in yield in dry years.

The share of fruitful shoots on a vine is 54%. The fruiting coefficient is 0.64, while the fruitfulness coefficient reaches 1.16. The mechanical properties of the clusters are high: the berries are firmly attached to the pedicel receptacle, the average separation force is 214–234 g, and the crushing resistance is 1074 g. The dense and durable skin provides the fresh crop with good transportability. The grape variety Irsai Oliver has a relative resistance to downy mildew (mildew). Due to the specific structure of the bush with long leaf petioles, the clusters are perfectly ventilated; therefore, the berries are weakly affected by gray rot (botrytis) and are able to remain on the bushes for a long time without losing their commercial and taste qualities. The frost resistance of the variety is medium: the average long-term visual assessment of the condition of the bushes after winter is 3.7 points on a five-point scale, and damage to buds exceeding 50% is observed when the air temperature drops to minus 19 °C.

Winemaking and Features of the Finished Product

The grape variety Irsai Oliver is a very valuable technological component for winemaking, primarily for the production of high-quality dessert wines. The dense skin of the berries allows the harvest to be left on the bushes for raisining and reaching the conditional sugar content required for the dessert direction. The muscat juice from these grapes has a very high quality. The finished dessert wine is characterized by a beautiful golden color, a clean and pronounced muscat-citron aroma with a noble hint of rose, as well as a delicate buttery taste, receiving the highest sensory evaluation scores at the level of 9–9.2 points. Also, the grape variety Irsai Oliver is used for the preparation of natural semi-sweet wines, a striking example of which is the blend wine Lada (prepared jointly with the Sukholimanskii belyi variety). This wine is distinguished by a delicate muscat aroma, a light harmonious taste, and is evaluated by experts at 8.6–9 points.