Preparation and storage of grapevine cuttings for grafting.

Vine harvesting is carried out in intensive-type nurseries or in standard fruiting vineyards that have passed approval and mass selection. The timing of harvesting, storage methods, and quality requirements for rootstock material are the same here as when growing own-rooted nursery plants. The main task of pre-grafting preparation is to restore the water balance in the vine tissues and activate metabolism, which directly affects the graft take rate.

Sorting, grading, and soaking of cuttings

Preparation of the rootstock begins 15–20 days before grafting work starts. The vine is removed from storage and transferred in batches to the preparation room. Depending on regional standards, it is cut into cuttings 35–49 to 50 cm long. The lower cut is made 3–4 mm below the node, and the upper one through the internode, strictly maintaining the standard length.

Cutting is combined with bud removal and material sorting. For small volumes, the vine is cut manually; for industrial scales, pneumatic pruners are used, and buds are removed using a PUG-1 semi-automatic machine. During the sorting process, all bent, dried-out, decayed, and browned cuttings are discarded. Vines with an excessively developed pith, short or overly long internodes, and non-standard thickness are also rejected.

After initial selection, the cuttings are graded by thickness. For manual grafting, the vine is divided into three groups based on the diameter of the upper cross-section: 7–8 mm, 9–10 mm, and 11–13 mm. If mechanized grafting is planned, grading is carried out in steps of exactly 1 mm. Sorted cuttings are tied into bundles of 100 and sent for moisture saturation.

Soaking is carried out in containers with soft water or in vacuum chambers. Water exchange triggers respiration and protein-carbohydrate metabolism processes in the tissues, which accelerates the fusion of the scion with the rootstock. With standard immersion, the process takes 48 hours, while in vacuum units it is reduced to minutes. Saturation with water can be combined with treatment with growth regulators.

• Optimal cutting humidity — 57–59%
• Water temperature for soaking — 15–18°C
• Working vine thickness range — 7–13 mm
• Standard soaking time — 48 h
• Saturation time in a vacuum chamber — 10–15 min

To protect against grey rot, bacterial necrosis, and black spot, cuttings are disinfected after soaking. They are immersed for 5 hours in a 0.5% solution of technical quinosol with an active ingredient purity of 98%. This treatment is a mandatory preparation stage for both rootstock and scion.

Local electric heating and stratification of tops

To obtain a circular callus formation at the junction of the components, local heating of the rootstock cutting tops is used. Unlike general heating of the entire vine, heat exposure only to the upper part yields the best results during grafting. To achieve this, the lower ends of the cuttings are kept cool, while the upper ones are heated using electric elements.

1. Debudded and cut rootstock cuttings are tied into bundles.
2. After soaking in water or a 0.5% quinosol solution, the bundles are placed with their lower ends on a platform covered with a 5–7 cm layer of moist sawdust.
3. The platform is enclosed with wooden boards 100–120 cm high.
4. The bundles are layered with sawdust, and the space between the outer rows and the boards is tightly filled with a heat-insulating layer of sawdust up to 5–6 cm thick.
5. Sawdust is poured over the bundles in a 4–5 cm layer, covered with polyethylene film, and an EFI-14 group electric heater is placed on top.
6. The heater is connected to an ESU-2M or UES-6 unit, covered with film on top, and a 7–8 cm layer of moist sawdust is added.
7. A second tier of cutting bundles is placed vertically on this layer — morphologically with the top ends down, towards the heat source.
8. The entire two-tier stack is covered from the top and sides with an 8–10 cm layer of sawdust for protection against drying out.

Thanks to this design, the heat from the heater is distributed unevenly. A high temperature is maintained in the top zone, stimulating cell division, while the heel of the cutting remains cool. This inhibits premature development of the lower part of the vine during stratification.

Pre-planting stratification of the rootstock cutting tops lasts from 3 to 6–8 days. As soon as this period expires, the prepared rootstock is immediately sent to the grafting tables. A delay at this stage can lead to callus overgrowth and poor graft take.