Börner

History of Origin and Viticultural Significance

The Börner rootstock represents an outstanding achievement of German academic breeding aimed at completely overcoming the phylloxera crisis. The history of the cultivar's development began in the first half of the 20th century, when German scientist Carl Börner experimentally established that the wild American grapevine Vitis cinerea Arnold possesses not merely tolerance, but absolute immunity to phylloxera, completely depriving the insect of its ability to feed. However, due to extremely low rooting rates of cuttings and poor grafting compatibility, this species could not be used directly in vine nurseries. To overcome this limitation, Börner conducted an extensive series of interspecific crosses.

In 1936, a controlled cross was performed at the Imperial Biological Institute in Naumburg, utilizing Vitis riparia 183 Geisenheim and Vitis cinerea Arnold as parent partners. The resulting seedlings were planted in 1943 in an examination field in the Zellertal (Palatinate). In 1964, the most promising plants were transferred to the Geisenheim Grape Breeding Institute, where the final selection of a single clone was carried out under the direction of Dr. Helmut Becker and the direct supervision of the institute's director, Dr. Ernst Rühl. The selection number of this seedling is registered as Na 5153-54 according to official US Patent data (US PP09575P), and as Na 5152-54 according to the VIVC international database. In 1989, the Börner variety was officially registered in the German National Plant Variety Catalogue under the registration number RBU 15, and the cultivar was named in honor of its original breeder.

The primary viticultural significance that distinguishes the Börner rootstock from other Franco-American hybrids is its 100% absolute immunity to all known aggressive strains of phylloxera, affecting both root and foliar forms of the pest. Furthermore, this Boerner rootstock variety displays a pronounced, effective tolerance to Xiphinema index and Longidorus attenuatus nematodes, which serve as the primary vectors for the transmission of the dangerous grapevine fanleaf virus. Practical trials in various wine-growing regions of Europe have confirmed that the Börner rootstock ensures excellent affinity, guaranteeing stable vigor, high productivity, and premium fruit quality of the scion at the level of standard rootstocks such as SO 4, 5 C, 5 BB, and 125 AA. In specific adaptation trials, the Börner grapevine rootstock also demonstrated superior tolerance to drought conditions compared to all other widely distributed rootstock cultivars.

Ampelographic and Botanical Description of the Börner Rootstock

The morphological characteristics of the rootstock partially resemble those of the parent species Vitis cinerea, particularly in the structure of the growing tip and mature leaf form, but it is distinct in its earlier wood ripening stages.

• Young Shoot (Growing Tip): The growing tip is half-opened (half enclosed by small leaves) with a strong intensity of striped anthocyanin coloration. The density of prostrate hairs is extremely high (very dense), accompanied by sparse to medium dense erect hairs.
• Mature Shoot: The dorsal sides of internodes and nodes are green. The ventral sides of internodes are green with distinct red stripes, and the ventral sides of nodes are completely red. The shoot features a medium overall intensity of anthocyanin coloration. Erect hairs on nodes and internodes are distributed with a medium to high density. The shoot attitude ranges from semi-erect to horizontal. Laterals possess moderate vigor.
• Tendrils: Distributed discontinuously along the shoot. Tendrils are 3-branched, wine-red in color, with a length ranging from 0.24 to 0.37 m. A few single woody hairs are present at the base, along with a sparse to medium dense distribution of erect hairs.
• Young Leaf: The upper side of the young leaf blade is copper-yellow to yellow with a medium intensity of anthocyanin coloration. Between the veins, the density of prostrate hairs is dense to very dense, while erect hairs range from sparse to medium density. On the main veins, prostrate hairs are sparse, whereas erect hairs are densely distributed.
• Mature Leaf: The leaf blade is large, 21–23 cm long, and cordate-shaped. The leaf is virtually entire or possesses zero to three very weak lobes, with a flat blade profile. The upper side of the blade is dark green with weak blistering; there is no undulation of the blade tissue between the main and lateral veins. The marginal teeth are straight, short to medium in length. The petiole sinus is slightly open, closed, or features slightly overlapping lobes, with a distinctly V-shaped base. Anthocyanin coloration of the main veins is weak to medium on the upper side of the blade, and absent or very weak on the lower side. On the lower side of the blade between the veins, prostrate hairs are of strong density, while erect hairs are very sparse or entirely absent. On the main veins on the lower side, prostrate hairs are sparse, whereas erect hairs are medium to dense in concentration. The petiole is at least 17 cm long, featuring sparse to medium dense prostrate hairs and very dense erect hairs.
• Flower: The flower type is male. Flower clusters are medium-sized, measuring 0.16 to 0.21 m in length. The flower consistently forms six anthers. Pistils are weakly developed and present only occasionally in a slight, vestigial, sterile form. The fertile pollen is light yellow in color; each flower cluster produces approximately 0.5–0.7 g of pollen.
• Woody Cane (Mature Wood): The cross-section is elliptic, and the surface is distinctly striated. Lenticels are absent. The main color of the mature cane ranges from medium to dark brown with reddish-brown longitudinal stripes. Nodes and internodes exhibit dense to very dense erect hairs. The internode length ranges from 0.21 to 0.28 m, and the cane thickness varies between 0.06 and 0.14 m. Bud burst is early.

Nursery Management and Agrotechnical Features

The Börner grapevine rootstock demonstrates exceptional technological performance under nursery and motherblock plantation conditions. In the climatic zone of the Rheingau, when pruned to 6–8 shoots per plant, the Börner rootstock variety provides a stable annual yield of 50 to 70 high-quality, graftable cuttings of standard length (0.40 cm) per вегетационный вест. The shoots feature early wood ripening, achieving mature wood lengths of up to 4.00 meters per shoot by the end of the season when grown in self-rooted motherblocks.

The cultivar possesses an outstanding natural immunity to both foliar and root forms of phylloxera: upon insect feeding, the plant tissue instantly isolates the site through localized necrosis, completely blocking the pest's lifecycle. This allows nursery managers to totally eliminate chemical treatments against phylloxera in motherblock plantations. Cuttings display rapid callus formation dynamics and high rooting rates in the field nursery. When bench grafting is performed, the Börner rootstock guarantees a secure, complete circular union and a high yield of top-tier first-grade grafted vines with major commercial Vitis vinifera cultivars.