Riparia x Rupprecht 3309 — this is a grapevine rootstock developed by the French breeder Cuderc in 1881. It is widely used in viticulture in France, Romania, Italy, as well as in the northeastern United States and Canada. This rootstock is characterized by high resistance to fungal diseases such as mildew and oidium, as well as high resistance to phylloxera root form. However, it is sensitive to viral diseases and nematodes. The winter hardiness and frost resistance of the rootstock are at a high level, allowing it to be successfully grown under various climatic conditions. Riparia x Rupprecht 3309 grafts well with most European grape varieties, ensuring stable and high-quality fruiting. First-generation hybrids based on Riparia x Rupprecht 3309 occupy an intermediate position between parental forms, showing less soil requirement. The vines have medium growth vigor, shoots mature well and relatively early. The rootstock is adapted to various soil types, including well-heated sandy, loamy, sandy-clay, and clay-limestone soils with low carbonate content. However, it can tolerate no more than 20% total limestone and 11% mobile lime, while its salt tolerance and drought resistance are low, and waterlogged soils are undesirable for it. Riparia x Rupprecht 3309 is characterized by medium height, with an annual growth volume of about 0.06 m³ per bush and average shoot length of 2–2.5 meters. By the end of the vegetation period, the vines reach 70–75% maturity. The root system is spreading, wide, and well-branched, which facilitates good rooting of cuttings and reliable grafting with scions. The vegetation period lasts about 180 days with an active temperature sum of approximately 3000°C. The rootstock is widely used in industrial cultivation of technical grape varieties, promoting compact bush formation with high-quality yields.
