Narrative
Type = Tetraploid. Per Galet (see citation): "ORIGIN: This rootstock was selected by the viticulture school of Oppenheim, Germany, from Teleki's Berlandieri-riparia No. 4 (see origin 5 BB); SO 4 is an abbreviation of Selection Oppenheim No. 4. DESCRIPTION: Growing tip: downy, white with rose margin. Young leaves: cobwebby, green, more or less copper. Leaf: cuneiform, 136-3-24, entire, lateral sinuses 10, dull, yellowish, wavy, with upturned edges; petiolar sinus with a narrow V on narrow leaves which becomes an open U when adult; teeth convex, nearly flat; petiolar junction pink; petiole and veins pubescent. Flower: always sterile, male. Shoot: ribbed, purple nodes, slightly pubescent especially on the nodes. Cane: finely ribbed, glabrous with a few pubescent hairs on the nodes, dark chocolate brown, nodes inconspicuous; small, pointed buds. APTITUDES: This is a vigorous rootstock which develops especially rapidly at the start and, like Riparia tends to favor fruit set and advance maturity. In field trials in the Champagne district, the vines grafted on SO 4 had a greater average production than those on 161-49 C or 41 B, but slightly less than on 5 BB. In the Mediterranean region, SO 4 has been criticized for its slender trunk, which may fail to support a nontrelised, head-pruned vine with a heavy crop. Suited to humid, clay soils, it is not recommended for very dry conditions. Its resistance to active lime is approximately 17 to 18 percent and it has a good resistance to nematodes. According to Vidal and Marcelin (1968), it accepts up to 0.4g/kg salt content. SO 4 roots well. It field grafts well and bench grafts satisfactorily. It produces a large amount of propagating wood. Introduced in France in 1941, there was an extensive planting of mother vines mainly to satisfy the demand for graftable cuttings in Germany. It is now the number one rootstock variety in France." Per Winkler (see citation): "SO 4 has only recently been placed in field trials in California vineyards. The moderate vigor of its scions indicates that it may not be suitable on high stress sites. For example, in a non-irrigated trial in Napa Valley, it has developed slowly, producing relatively small vines during the first few years. On the other hand, it may be quite satisfactory on irrigated, more fertile sites. This new stock to California deserves a thorough and intensive study in phylloxerated districts."