420A

History of Origin and Economic Significance

The grape rootstock Berlandieri x Riparia 420A was obtained in France in 1887 by viticulturists Millardet and de Grasset through the artificial crossing of Vitis berlandieri and Vitis riparia. The rootstock Berlandieri x Riparia 420A is recognized as one of the best chlorosis-resistant rootstocks, which led to its distribution in France, Italy, Bulgaria, Romania, Hungary, Germany, as well as in Moldova, Ukraine, and Georgia.

The main economic advantage of the Berlandieri x Riparia 420A variety lies in its high resistance to high lime content in the soil. According to researchers, this rootstock variety tolerates up to 60% of total lime content in the soil, being second in this indicator only to the Chasselas x Berlandieri 41B hybrid. The rootstock tolerates up to 20% of active (soluble) lime content. The root system of the variety develops a relatively small number of main roots compared to Kober 5BB, but they branch intensively and penetrate deeply into the soil horizons, thanks to which the grape rootstock Berlandieri x Riparia 420A tolerates drought periods quite well.

European standard grape varieties grafted on Berlandieri x Riparia 420A rootstock develop slowly in the first years after planting, but starting from the second or third year they demonstrate fast and vigorous growth, outperforming similar scions on hybrid combinations of Riparia x Rupestris. Vineyards using the Berlandieri x Riparia 420A rootstock are characterized by regular fruiting and high longevity, which is confirmed by many years of its cultivation practice in Kakheti conditions.

Morphological Description of the Rootstock Variety Berlandieri x Riparia 420A

Botanical traits and morphology of the rootstock organs were described in detail on mother plantations in the village of Vazisubani, Georgian SSR:

• Young shoot (tip): the apex is covered with sparse cobwebby pubescence and has a greenish-white color with a bright pink border along the edges. The first two young leaves are yellowish-green with a brownish-red tint, covered with bristly down on the lower side. The shoot axis is ribbed, light green, with sparse cobwebby pubescence; on the side facing the sun, it has a dark wine-red color with dark purple nodes.
• Mature leaf: has a medium size and a wedge-shaped form, three-lobed, with faintly marked upper sinuses and absent lower ones, almost entire. The texture of the blade is dense and rough. The upper side of the leaf is dark green and bears an barely noticeable down. On the lower side of the leaf, the veins are covered with weak bristly pubescence.
• Teeth and petiole: teeth at the ends of the lobes are large, triangular with a wide base and a narrow apex elongated into a sharp point. Marginal teeth are small, triangular, with convex sides and a sharp apex. The petiole is shorter than the midvein of the leaf, colored wine-red on the sunny side, covered with sparse bristly down, which becomes denser in the area of the groove. The bases of the main veins are light brown.
• Mature shoot: the annual cane is characterized by a ribbed, rough surface. The color varies from brown to rusty-brown, turning into a dark gray-brown tint in the lower part of the shoot. Distinct dark brown stripes along the internodes serve as a characteristic variety trait.
• Reproductive organs: the flower type is male, the inflorescences are of medium size and contain 5–7 stamens. After flowering is complete, the inflorescences drop completely, and the Berlandieri x Riparia 420A variety does not form berries.

Features of Agricultural Practices in Nursery Production

The Berlandieri x Riparia 420A variety belongs to late-flowering rootstocks; the flowering phase occurs in the first decade of June, which is 3–8 days later than other common grape rootstock forms. The duration of the growing season from bud break to leaf fall is 199 days with a sum of active temperatures of 4065 °C. Annual shoots by the time of mass leaf fall are characterized by a high degree of wood ripening, reaching 90% and more. The growth vigor of the cane depends on the soil type: on rich alluvial, chernozem-like, and chestnut areas, the Berlandieri x Riparia 420A rootstock grows vigorously, while on poor podzolic lands the growth weakens.

The productivity of mother plantations is high, the variety yields a significant number of uniformly thickened cuttings. On the mother plantations of Imereti (Western Georgia), the yield of standard cuttings with a length of 110 cm is about 65 thousand pieces per hectare, in Kakheti (Eastern Georgia) the productivity is slightly lower — 42.6 thousand cuttings per hectare. To achieve the maximum yield of cuttings, it is recommended to maintain a load within 15–20 shoots per vine and perform fivefold suckering (lateral shoots removal), which increases the yield of material suitable for grafting by 48–63%.

The main technological disadvantage restricting the distribution of the variety in nursery production is the insufficient rooting ability of cuttings. In experimental conditions, the yield of first-grade own-rooted stumps from the nursery field was 84.6% with a shoot growth length of 44 cm, which is noticeably inferior to the indicators of the industrial standard Kober 5BB. Due to reduced rooting, the total yield of first-grade grafted plants from the nursery field remains low, despite a completely satisfactory grafting compatibility with scions.

*Publisher's note: the ampelographic overview is compiled based on the variety description from the book "Ampelography of the USSR. Little-distributed grape varieties", Volume III, published in 1966. The text has been processed and edited only in terms of formatting, while, for the sake of preserving the authenticity of historically valuable material, the formulations and style of description inherent in the Soviet ampelographic school were not changed.