Preservation technologies and preparation of grafted grape scions for planting

Winter grafting of grapevines allows for a significant increase in the annual output of nursery plants and helps distribute the workload in the nursery more efficiently. Shifting the schedule to winter frees up grafting workshops and stratification chambers during the busiest spring period. To keep the grafted material viable until spring planting, artificial cold storage technologies are used.

Conservation methods for grafted cuttings

Winter grafting begins from the second half of January. The choice of conservation technology depends on how the stratification of cuttings is carried out — in water or using a moisture-retaining substrate.

• Storage temperature after stratification — 2–5 °C
• Storage temperature before stratification — 0–2 °C
• Treatment time with chinosol solution before bandaging — 1–2 s
• Thickness of the sawdust layer for conservation — 8–10 cm

When using a moisture-retaining substrate, cuttings are conserved after stratification in special refrigeration chambers. To do this, the following steps are performed:

1. Carefully remove the top layer of the moisture-retaining substrate from the boxes with grafted cuttings.
2. Spray the tender green shoots of the scion with a 0.1% chinosol solution to protect against mold.
3. Cover the cuttings again with a layer of dry sawdust 8–10 cm thick.
4. Transfer the boxes to a refrigerator and keep them until spring at a temperature of 2–5 °C. Harden the plants in the open air 5–7 days before planting.

If stratification is performed in water without a substrate, the cuttings must be conserved before sprouting begins. To prevent cell death at the junction of the components, the surface of the grafting cuts must be bandaged with polyethylene film. For better preservation, before bandaging, the cuttings are dipped for 1–2 seconds in a 0.2–0.3% aqueous solution of chinosol. The prepared material is stored in refrigeration chambers at a temperature of 0–2 °C in a controlled gas atmosphere. 20–25 days before planting in the nursery, these cuttings are taken out, stratified, and hardened using the standard method.

Hardening and planting cuttings in the nursery

Hardening adapts plants to the natural conditions of the open soil. 7–10 days before planting in the nursery, the cuttings are taken out of storage and sorted into two groups. The first group includes cuttings with circular callus formation, sprouted or swollen buds, and root primordia on the rootstock. The second group includes cuttings without circular callus and without signs of bud swelling. During sorting, it is essential to remove all shoots on the rootstock and roots that have formed on the scion.

If necessary, the sorted cuttings are waxed. If waxing has already been carried out, they are immediately placed in groups into boxes whose bottom and walls are lined with film to a height of at least 10 cm. Water or a hydroponic solution is poured into the boxes to a depth of up to 5 cm with the addition of a 0.005% heteroauxin solution, ensuring that the bases of the rootstocks are submerged in the liquid.

Boxes with cuttings of the first group are placed under a canopy or in a bright, unheated room under film for 3–4 days, and then hardened in the open for another 7–10 days. If the temperature drops at night, the boxes are covered with mats. After this, the plants are planted in the soil. After sorting, cuttings of the second group are returned to the greenhouse for 4–6 days for further development, after which they are also planted. Bandaged cuttings are usually planted in the nursery immediately after stratification without prior hardening.

Planting in the nursery is carried out mechanically to a depth of 25–30 cm. The planting window is limited — all work must be completed by mid-May. Planting patterns and planting density are shown in the tables below.

The height of the grafting site above the soil level is chosen depending on the climatic conditions of the region and the cutting preparation technology.

The same as for cuttings planted in a nursery for growing own-rooted grape nursery plants. A specific feature of the grafted nursery agrotechnics is performing two to three inspections (katarovka) in June–July, which ensure better conditions for the rootstock to unite with the scion. To this end, grafted cuttings are slightly uncovered, and roots that have developed on the scion and shoot growth on the rootstock are removed at the junction of the components. The first inspection is carried out during the period when most plants form a tendril, the second one — 25–30 days after the first one with a slight lowering of the mound... In the second half of September, the plants in the nursery are hilled up to 3–4 buds to prevent damage to the scion by early autumn frosts. At the end of the growing season (August – beginning of September), the nursery plants are inspected to remove impurity cultivars and nursery plants with signs of viral diseases. 10–15 days before digging up the nursery plants, defoliation is applied using a solution of 60% magnesium chlorate powder magnesium (7 kg/ha). Spraying is performed in the morning on a cloudy day so that the droplets of the preparation do not dry out.