Solonis

Origin and Economic Significance

The grape rootstock Solonis is a wild hybrid native to the United States, specifically found in the Red River basin across regions of New Mexico and Texas. The first descriptions and examinations of its specimens in Europe date back to 1835–1847. For a long time, the origin of this form remained uncertain; researchers T.V. Munson and P. Viala later identified the form in its native habitat and established its identity with the Novo-Mexicana group. The natural origin of the Solonis rootstock is attributed to the hybridization of Vitis riparia and Vitis candicans (according to A. Millardet, Vitis rupestris might have also contributed to its genesis)*.

This rootstock variety Solonis was actively utilized during the initial stages of overcoming the phylloxera crisis in France. The popularity of the form was driven by its high vigor, excellent rooting capacity of cuttings, and strong graft compatibility. In long-standing vineyards over 30 years old, the rootstock demonstrates stable yields and sustains the vegetative vigor of the grafted scion pairs.

The primary viticultural advantage of the Solonis rootstock lies in its adaptability to cool, humid, and saline soils. The form can withstand up to 20–25% of active lime (calcium carbonate) in the soil. However, when planted on dry sites under heavy phylloxera pressure, the root system showed insufficient resistance to the pest. Consequently, the Solonis grape rootstock largely surrendered its commercial position to its improved selection, the 1616 rootstock.

Morphological Description of the Solonis Rootstock Variety

• Vine: Vigorous, characterized by a spreading growth habit and the development of a thick trunk.
• Shoots: Long, cylindrical in cross-section, smooth. In the herbaceous stage, they exhibit an intense dark purple coloration; the mature cane turns a light grayish-brown shade. Internodes are elongated, and nodes are weakly prominent. A tufted whitish pubescence is observed, localized primarily around the nodes. Tendrils are intermittent, bifid, and covered with persistent downy hair.
• Leaves: Medium-sized, entire. The petiolar sinus is shallow with a wide, open clearance. The leaf blade is folded in a gutter-like shape, with the apex curved downward. The margins bear two rows of sharp teeth; the terminal teeth of the lobes are elongated and oriented toward the central axis of the leaf. The upper and lower surfaces of the blade are glabrous except for the veins: stiff whitish hairs are present along the veins on the underside, and rare flocculent pubescence occurs on the upper surface. The upper side is glaucous-green, while the lower side is a paler green.
• Flower type: Functionally female.
• Bunches and berries: The mature bunch is small, irregular in shape, and loose. Berries are small or slightly below medium size, globose, or sometimes slightly flattened (discoid). The skin color is deep black, covered with an intense waxy bloom (pruina). The skin is thick and astringent; the flesh is juicy, melting, and high in acidity. Seeds are small.

Cultural Characteristics in Nursery Management

Under nursery conditions, the Solonis rootstock displays strong affinity with European grapevine scions (Vitis vinifera). Cuttings root easily during propagation, ensuring a high yield of standard planting material. Due to its high vigor, mother vines produce long canes. When planning vineyards, this Solonis rootstock variety should be reserved exclusively for sites with sufficient moisture, cool subsoils, or areas at risk of soil salinity, completely avoiding its establishment on drought-prone slopes.

*VINEYARD Note: The parental pair Riparia × Candicans originally claimed by researchers proved to be an error. After DNA research tools became available to scientists, the origin of Solonis was definitively established as an interspecific hybrid of Vitis riparia Michaux × Vitis longii.