Effective technologies for the rapid propagation of rare grape cultivars

Accelerated propagation methods for grapes allow for the rapid production of high-quality nursery plants of scarce cultivars. If conventional nursery plants are in short supply, nurserymen use green or shortened woody cuttings. These methods require strict control of temperature and humidity but ensure high plant survival rates.

Growing nursery plants from green cuttings

For mass propagation using green cuttings, plastic greenhouses or hotbeds equipped with misting systems are used. The soil within them must be well-drained. A layer of sand is spread over prepared beds 1.2–1.4 m wide, and sprayers for intermittent fine-mist irrigation are installed in the center of the beds.

• Air temperature — 20–30 °C
• Optimal humidity — 65–85% (100% on hot days)
• Sand layer thickness — up to 4 cm
• Growing period — 1–1.5 months

1. Place the cut shoots into containers with water, move them to a cool place, and cover to prevent drying.
2. Cut the shoots into two-bud cuttings using a sharp knife or razor blade. Make a straight cut directly below the node on the side opposite to the bud.
3. Completely remove the lower leaf and trim the upper one by half, then place the bottom ends of the cuttings in water.
4. Plant the cuttings using a 10x10 cm spacing at a depth of 2–3 cm. The base of the cutting should be in the moist sand without touching the soil underneath.

During the rooting period, it is important to prevent the soil from drying out. To achieve this, the automatic irrigation system is set to deliver water for 3–5 seconds every minute, reducing the frequency or switching it off completely at night. Maintenance includes regular loosening of the soil, 2–3 applications of mineral top dressing, and plant protection against diseases. As the roots develop, irrigation is reduced, and 5–7 days before transplanting into the nursery row, the plastic film is removed to harden off the plants. By this time, the green shoots reach a length of 20–30 cm.

Propagation using shortened woody cuttings

This method relies on the use of well-matured canes, from which one- or two-bud cuttings are cut in the spring. One-bud cuttings are made 5 cm long with the bud exactly in the middle. For two-bud cuttings, the bottom cut is made at a right angle, and the top cut 1.5–2 cm above the bud on the side opposite to it.

1. Soak the cut cuttings in water for 1–2 days and store them in plastic bags.
2. Before planting, soak the cuttings again and place them in a greenhouse for stratification at a temperature of 22–23 °C and humidity of 90–95%.
3. Insert the cuttings tightly into moist sand and cover them with the same, leaving only the top bud exposed.
4. After the formation of callus and root primordia, plant the cuttings into paper cups or peat blocks with a mixture of sod soil, humus (1:1), and 3–5% river sand.
5. Transfer the cups in crates to a plastic greenhouse and cover with sand so that the top bud protrudes 2–3 cm above the surface.

With early spring planting, the cuttings can be planted directly into the greenhouse soil without cups. In this case, they are buried up to the top bud either vertically or at a 45° angle. The microclimate parameters and maintenance schemes for this type of cultivation are presented in the table.

On the 25th day after planting, the nursery plants begin to be hardened off: the temperature in the greenhouse is gradually lowered and light exposure is increased. Plants are transferred to the nursery row once the threat of spring frosts has passed. For transplanting, it is best to choose overcast days, early morning, or evening.

Propagation by layering is used in regions where own-rooted grape culture is practiced to quickly obtain new nursery plants. The method allows for the production of up to 20 developed vines from a single plant in one growing season. Woody shoots are laid down in the autumn after harvesting or early in the spring, while green shoots are laid down during their active growth phase.

To correctly establish the layers, prepare trenches on both sides of the vine. Lay the canes into them, following the recommended technical parameters. This will ensure high bud survival rates.

1. Select 2–3 of the strongest, longest, and undamaged shoots at the base of the bush.
2. Remove all leaves, tendrils, and lateral shoots from them.
3. Lay the shoots horizontally in the trenches along the row and secure them with garden pins in 2–3 places.
4. Apply well-rotted manure or humus to the bottom of the trenches, cover it with soil mixed with superphosphate and potash salt.
5. Cover the laid shoots with a thick layer of loose soil and water abundantly.

Throughout the entire growing season, the layers require regular care. Water and fertilize the plants, loosen the soil, perform shoot thinning, and tie up the developing green shoots. For protection against disease, be sure to carry out preventive spraying against downy mildew. In autumn, after leaf fall is complete, carefully dig up the layers, separate them from the mother bush, and cut them at the internodes into individual nursery plants.

Green grafting: propagation in phylloxera-infested zones

In areas with a high risk of phylloxera infestation, green grafting becomes the primary method for the accelerated propagation of scarce cultivars. Work is carried out directly in the vineyard during the growing season. The main condition for successful union is the active growth of the rootstock, scion, or both components simultaneously.

• Grafting period — from mid-May to mid-June
• Length of rootstock shoots for work — 15–20 cm
• Grafting height for trunk formation — 80–100 cm
• Binding tape width — 1–2 cm
• Time for component union — 15–20 days
• Water temperature for soaking cuttings — 20–25 °C

In simple whip grafting, a single-bud green scion cutting is joined with a slanting cut to a green rootstock shoot. To do this, the mother bushes of phylloxera-resistant cultivars are pruned to the "black head" in spring and slightly hilled. Once the shoots grow out, grafting begins.

1. Leave 4–8 of the strongest shoots located at the base on the prepared rootstock bush, and remove the rest.
2. On the day of grafting, completely clean the remaining rootstock shoots of leaves, tendrils, and buds.
3. Prepare single-bud cuttings from high-yield scion bushes directly on the day of work.
4. Join the components with a slanting cut without a tongue at the base of the bush or at the required height for the trunk.
5. Wrap the union site tightly with PVC film or a rubber strip, and cover with soft paper on top to protect against dehydration.

After grafting, water and hill the mother bushes abundantly, and throughout the summer, regularly remove all new growth from the head of the bush. Two to three weeks later, remove the binding material. Before leaf fall, cut the matured grafted shoots, sort them, and put them into storage for spring planting.

For grafting green shoots with lignified cuttings, use scion material harvested in autumn. The operation is carried out during the period of active sap flow, when sap appears on the cut surfaces of the rootstock. Before starting work, cut the vine into single-bud cuttings.

• Graft success rate — at least 90%
• Budding dates — from late July to early August
• Cleft green grafting dates — from mid-May to late June
• Worker output per season — up to 15,000 grafts

Green grafting is one of the fastest ways to propagate a rare grape cultivar and obtain the first harvest as early as the following year. This method allows for the efficient use of the existing rootstock stock without wasting time on growing new bushes. With proper care, tissue healing occurs quickly, and the vine has time to fully mature before the autumn frosts.

Green grafting by slanting cut and budding

Simple green grafting is performed directly on the rootstock shoots. A slanting cut 2–3 cm long is made at the required height, and a similar cut is made on the single-bud scion cutting just below the bud. Both surfaces must match in length and width for maximum tissue contact. The cuts are joined while moist, pressed tightly together, and bound with film.