Berlandieri x Riparia SO4, also known as Oppenheim SO-4, is a powerful and widely used grapevine rootstock obtained by crossing Vitis berlandieri and Vitis riparia. This variety was developed in Germany in 1919 and is characterized by strong growth, a robust root system that penetrates deep into the soil up to 2 meters, and significant resistance to various adverse factors. The vegetative period lasts approximately 179-180 days with an accumulated heat sum of about 3270-3300 °C. The cane matures to 80-90%, with an average shoot length of 4.5-5 meters and long internodes of about 14 cm. Leaves are large, dark green, with characteristic pubescence and shape, and flowers are male, resulting in no clusters on the rootstock.
SO-4 rootstock exhibits high resistance to phylloxera, mildew, oidium, and nematodes, making it particularly valuable for viticulture. The variety has moderate drought tolerance and high bud winter hardiness, although root frost resistance is somewhat reduced. It adapts well to various soil types, including acidic, moderately alkaline, clay-sandy, and carbonate-containing soils, allowing successful cultivation in diverse climatic conditions, including northern regions. However, the rootstock is less tolerant to waterlogging and spring flooding.
Agronomically, it is recommended to form bushes using the head-training method, leaving 10-12 two-bud spurs and 20-24 green shoots, using vertical high trellises with 4-6 wires, and planting density of approximately 2000 vines per hectare. Cuttings root well, but the grafting process may be slow, requiring extended stratification. SO-4 enhances grapevine yield, winter hardiness, and longevity, improves plant nutrition, and grafts well with European grape varieties. Despite some difficulties in magnesium uptake on poor soils and slower radial stem growth, this rootstock remains a versatile and reliable choice for viticulturists.
