Pre-grafting preparation and selection of grape cuttings for grafting

Quality inspection and preparation of scion cuttings

The success of bench grafting in grapes directly depends on the vitality of the buds on the scion vine. If damaged or weakened material is used, the take rate will drop sharply, and the bushes will grow weak. The quality of the buds must be checked in storage two weeks before the start of grafting work.

To determine the vitality of the buds, the following steps are performed:

1. Take a representative sample of 50–100 cuttings from different parts of the stack for each cultivar.
2. Cut the selected vine into single-bud cuttings so that the total volume of the sample is at least 500 units.
3. Spread the prepared segments in layers on damp burlap in a room with a temperature of 28–30 °C.
4. Regularly moisten the burlap, preventing it from drying out.
5. After 10–14 days, count the sprouted and non-sprouted buds.

After assessing the quality, proceed to calibrate the vine by the diameter of the upper section. The cuttings are sorted into three groups corresponding to the rootstock gauges. During the sorting process, substandard shoots affected by necrotic spotting, dried-out or browned ones, and vines with frayed buds are discarded.

• Minimum cutting diameter — 7 mm
• Maximum cutting diameter — 13 mm
• Soaking temperature — 15–18 °C
• Vine soaking time — 12–14 h
• Scion storage temperature — 10–15 °C
• Storage time in bags — 3–4 days

The sorted vines are cut into single-bud segments. The upper cut is made 1.5–2 cm above the bud on the opposite side, and the lower cut is made straight 4–6 mm below the bud. The prepared material is soaked in clean, low-hardness rainwater and then lightly aired out. Afterward, the cuttings are categorized, packed in plastic bags, and kept in a cool place before being sent for grafting.

Compatibility of components and selection of rootstock-scion combinations

The rootstock vine is not capable of inducing genetic changes in the scion cultivar, but it significantly influences the physiology of the bush. A properly selected rootstock regulates shoot growth, accelerates or slows down the progression of the growing season, and determines the volume and quality of the future harvest. All these changes are of a modification nature and are not passed on to subsequent generations during propagation.

The vitality of the grafted plant and the strength of the union between components depend on affinity — their mutual compatibility. This indicator is not constant for a specific pair of cultivars, as it is influenced by environmental conditions, the level of agricultural technology, and the age of the vineyard. The most reliable method for selecting a pair remains direct cultivar testing of various combinations under specific soil and climatic conditions.

Region	Cultivar	Best rootstocks
Moldova	Csaba Gyöngye, Chasselas blanc, Karaburnu, Riesling renano	Riparia X Rupestris 101–14, Riparia Gloire de Montpellier, Berlandieri X Riparia Kober 5BB
Moldova	Muscat blanc, Queen of the Vineyards	Riparia Gloire de Montpellier, Riparia X Rupestris 101–14, Riparia X Rupestris 3309, Berlandieri X Riparia Kober 5BB
Southern steppe of Ukraine	Csaba Gyöngye	Berlandieri X Riparia Kober 5BB, Riparia X Rupestris 101–14
Southern steppe of Ukraine	Chasselas blanc	Riparia X Rupestris 101–14, Riparia X Rupestris 3309, BerlandieriXRiparia Kober 5BB, SolonisXRiparia 1616
Southern steppe of Ukraine	Riesling renano	RipariaXRupestris 101–14, RipariaXRupestris 3309
Southern steppe of Ukraine	Muscat blanc	RipariaXRupestris 3309, RipariaXRupestris 101–14
Transcarpathia	Csaba Gyöngye	BerlandieriXRiparia Teleki 5C, Riparia Gloire de Montpellier, BerlandieriXRiparia Kober 5BB, BerlandieriXRiparia Teleki 8B
Transcarpathia	Chasselas blanc	BerlandieriXRiparia Kober 5BB, BerlandieriXRiparia Teleki 8B, BerlandieriXRiparia Teleki 5C, Riparia Gloire de Montpellier
Georgia	Most cultivars	BerlandieriXRiparia Kober 5BB, Chasselas XBerlandieri 41 B, BerlandieriXRiparia 420 A, RipariaXRupestris 3309, RipariaXRupestris 3306
Krasnodar Krai	Most cultivars	Chasselas XBerlandieri 41B, BerlandieriXRiparia SO 4, BerlandieriXRiparia Teleki 5C, BerlandieriXRiparia Kober 5BB

There are several ways to grow grafted grape nursery plants:

• 1 — bench grafting followed by stratification and planting of grafted cuttings into a nursery (the most widely used method);
• 2 — rooting rootstock cuttings and grafting onto them directly in the nursery;
• green grafting onto shoots on rootstock bushes with subsequent planting of grafted cuttings either in the nursery or in their permanent place.

Grape grafting can be carried out with dormant and green cuttings. The union of grafting components performed with dormant cuttings is facilitated by the formation of callus at the point of their connection — an outgrowth of white, loose tissue consisting mainly of an insoluble substance, the carbohydrate callose.

Callus formation proceeds as follows:

• During grafting, mechanical damage is inflicted on cells at the cut sites, causing their internal contents—plasma, cell sap, and organelles—to leak out.
• In the damaged cells, oxidative processes intensify while reductive processes diminish, leading to physical and chemical changes that result in the appearance of various compounds previously absent in the living protoplast of the cells.
• There is an increased influx of wound and growth hormones to the injury sites, which diffuse into the surrounding living cells.
• These cells, in turn, begin to divide intensively, giving rise to callus formation.

All living cells of annual shoots of grapevines are capable of such a reaction to wound irritation. Cells of the cambium, cortical parenchyma, and medullary rays form callus best, while cells of the phelloderm and phellogen do so less effectively. Other living elements of the secondary cortex do not participate directly in callus formation. Therefore, it is crucial that these tissues align when joining the scion and rootstock during grafting.

For callus formation, in addition to the presence of a wound, a specific complex of external conditions is required, in particular an appropriate optimum temperature and high air humidity, oxygen availability, and nutrients. The speed and nature of callus formation also depend on the degree of cane maturation, its carbohydrate content, and moisture saturation.

According to researchers, the union of grafting components occurs in a specific sequence:

Researcher	Publication Year
	1935
	1957

1. First, an isolating layer composed of destroyed and dead cells forms on the surface of the grafting cuts of the scion and rootstock.
2. Under the pressure of the growing callus in grafted canes, the isolating layer ruptures during the union process, and breakthrough windows appear through which the scion and rootstock calluses emerge and connect, forming a union bridge.
3. Simultaneously with callus growth, an intermediate cambium arises, which, by connecting with the cambium of the scion and rootstock, forms xylem and phloem elements.
4. Conducting bundles—vessels—form from callus cells at some distance from the cuts, first near the scion cut, and later—near the rootstock. In the callus connecting the rootstock to the scion, the vessels follow a tortuous path and later interconnect.

The process of callus formation in grafted woody canes proceeds unevenly on different sides of the shoot, which is explained by their dorsoventral (asymmetric) structure and varying nutrient content (transverse polarity). Due to this, a higher carbohydrate content is concentrated on the ventral side, less on the dorsal, then on the flat side, and the least on the grooved side. Enzyme activity proceeds accordingly. Therefore, callus forms better and faster on the ventral side of the shoot, where the elements of the cortex and wood are most developed, somewhat worse and weaker on the dorsal side, then on the flat side, and lastly on the grooved side of the shoot. As a result of the longitudinal polarity in grapevines, callus formation occurs first at the morphologically lower, acute end of the cut, and later at the upper, obtuse end, which explains the faster callus formation on the scion compared to the rootstock.

Fig. 33. Callus development on grapevine canes:

I — depending on the dorsoventral structure of the shoot: 1 — callus first forms on the ventral side; 2 — then on the dorsal side; 3 — expansion of callus on the ventral and dorsal sides; 4 — later on the flat side; 5 — lastly on the grooved side; 6 further expansion of callus; II — depending on "apicality": callus formation at the lower, acute end of the cut. It can be seen that callus first forms at the acute end of the cut, then it gradually grows toward the obtuse angle (according to Borovikov).

To ensure uniform circular callus formation at the connection point of the grafting components, which contributes to their strong union, it is necessary to minimize the negative phenomena of polarity in callus formation. This is achieved by increasing the physiological moisture of the canes prior to grafting (soaking), treatment with growth regulators, pre-planting stratification, a specific orientation of the cuts of the grafted components, and their tight connection.

Methods, timing, and technique of grafting. Many methods of grafting are known in viticulture: simple whip grafting (with an oblique cut without a tongue), tongue-and-groove grafting (with an oblique cut with a tongue), cleft grafting, side grafting, chip budding, budding, etc. The tongue-and-groove grafting method—using an oblique cut with a tongue—has gained the widest distribution in industrial viticulture for the production of grafted planting material. It ensures a fairly tight connection and good union of the grafted components. With this grafting method, oblique cuts on the rootstock and scion are made in such a way that its obtuse angle falls on the ventral or dorsal, most developed side.

Grafting is carried out from mid-March to the end of April. To extend the grafting period, it is started in January–February in a number of regions, followed by the storage of grafted cuttings.

The sequence of grafting depends on the timing of bud burst in the scion cultivars. Earlier, the rootstock Berlandieri x Riparia Kober 5BB, Riparia Gloire de Montpellier, and scion cultivars with a long bud burst period are used for grafting — Cabernet Sauvignon, Sauvignon, Merlot, Muscat Blanc, Karaburnu, Hamburg Muscat, Italia, Rkatsiteli, Cardinal; in the mid-term — Rhine Riesling, Italian Riesling, Aligoté, Chasselas groups, Tavriz, Pinot Gris, Muscat Ottonel; and later — Galan, Pearl of Csaba, Traminer Rose, Queen of the Vineyards, Saperavi Severny.

Grafting operations are organized as follows. In the grafting workshop, scion and rootstock cuttings that have undergone pre-planting preparation and sorting by diameter are regularly brought to the grafters' workstations. The grafter matches single-bud scion cuttings and longer rootstock cuttings of the same diameter by eye, uses a grafting knife to make oblique cuts on them, the length of which must be identical and approximately 1.5 times the diameter of the cutting. Tongues are cut on the sections, which are used to connect the scion to the rootstock.

The surface of the oblique cuts on the rootstock and scion must be even and smooth, and the length of the copulation cuts must be identical. The tongues are cut so that they start above the pith, reach its base at a slight angle, and are equal to 1/3 of the cut length. To meet these requirements, it is important that the grafting knife is sharp and the oblique cuts are made in one continuous movement of the knife. The tongue slot should run almost parallel to the plane of the oblique cut. The tongue should not be too short or thick, otherwise, the connection points of the tongues will be weak and break. To make it easier to join the components, the tongues are slightly bent with a knife, and then the scion tongue is inserted behind the rootstock tongue, taking care not to bend them.

It is important that the finished grafted cuttings have no gaps at the connection point between the scion and the rootstock, and that the scion bark tightly adheres to the rootstock bark. If these conditions are met, binding of the grafted cuttings is not required. Experienced grafters perform 800–1000 grafts per working day. The grafts made

Fig. 34. Manual grape grafting by oblique cut with a tongue (whip-and-tongue grafting):

/ — 1 scion; 2 — rootstock; 3 — cutting of oblique sections; 4 — cutting of tongues; 5 — oblique cuts with tongues on the rootstock and scion; 6 — finished grafted cuttings. by each worker are checked by an inspector. If there are gaps at the tongue connection points or the copulation cuts do not match, the grafted cuttings are rejected and returned for re-grafting.

Cleanliness must be maintained in the grafting workshop; tables must be regularly washed with hot water and soda, and knives must be periodically disinfected in a 0.5% solution of quinosol or formalin. Grafters must wash their hands periodically.

Mechanized grafting. Due to the fact that manual grafting accounts for about 20% of all labor costs for the production of nursery plants, requiring highly qualified workers, and the optimal timing for grafting is very limited (30–35 days), ways to improve grafting methods are currently being sought. In nursery farms in Moldova, Ukraine, Georgia, and the RSFSR, mechanized grape grafting on a stepped tenon is being widely introduced. Using a machine, the rootstock and scion shoots are cut into cuttings of a specified length and simultaneously sorted by the diameter of the upper section into 6 groups: 6–7; 7–8; 8–9; 9–10; 10–11; 11–12 mm. Then, using an MP–7A machine, a 1.5 mm thick and 7 mm high tenon and a groove are made on the rootstock and scion cuttings, after which the grafters manually select the components and connect them. Cuttings grafted in this way must not have gaps at the connection point, burns, or fraying of the cuts. In Ukraine, a reconstructed Bulgarian grafting machine has become widespread, with the help of which the grafted components are connected on an omega-shaped tenon. The productivity of these machines is 2 thousand grafts per

Fig. 35. Mechanized grafting:

/ — connection on 1 tenon; 2 — on 2 tenons; 3 — shaped tenon and groove of the Bulgarian grafting method. shift, or 2 times more than manually. With mechanized grafting, the interval between cutting the rootstock and scion cuttings and joining them must be no more than 1 hour, otherwise, good fusion of the components will not occur.

Mechanization of grafting and protection of the graft union

For large work volumes, manual labor is replaced by machinery. For this purpose, semi-automatic grafting complexes are used. One such complex consists of three machines: the first removes buds on the rootstock, the second cuts and calibrates the scions, and the third performs the grafting onto a single common thorn. The machine refreshes the cut surfaces of the components and joins them. For medium volumes, another semi-automatic machine, operated by a single worker, is suitable. It simultaneously makes slanted cuts on the rootstock and scion of the same diameter, cuts tongues, and joins the components.

Immediately after grafting, the union site must be protected from drying out. Without this, the tissues of the scion and rootstock will not fuse. Grafted scions are either placed in moist sawdust for stratification or immediately covered with paraffin or another plasticizer. In some farms, waxing is performed after stratification, immediately before planting in the nursery.

Waxing solves several tasks at once: it retains moisture in the cut zone, strengthens the mechanical connection of the components, and protects the buds from fungal disease. In addition, the film retards premature development of the bud and shoot. Before treatment, the tops of the scions are dipped in clean water or a solution of chinozol. The liquid fills the micro-gaps between the components and prevents the paraffin from penetrating into the joint, which could block fusion.

• Capacity of the grafting complex — up to 10 thousand grafts per shift
• Capacity of the single-component semi-automatic machine — up to 2 thousand grafts per shift
• Concentration of chinozol solution for joint protection — 0.5%
• Preliminary dipping time for scions — 1–2 s
• Immersion depth in paraffin — 16–18 cm (1/3 of the length)

Recipes for protective mixtures and film bandages

Special compounds are used for this work. A classic mixture consists of technical-grade paraffin (mark "D") with the addition of 2% bitumen and 3% rosin or wax for better elasticity. A formula of 94% technical paraffin, 3% bitumen, and 3% rosin is also used. A more modern and heat-resistant composition is "Viticol," based on paraffin, low-molecular-weight polyisobutylene, and rosin ester. Polyisobutylene makes the coating resistant to melting in the sun.

Component of the "Viticol" mixture	Mass for the first preparation stage, kg
Paraffin (first portion)	2
Polyisobutylene	0.5
Glycerol ester of tall oil rosin	0.3

1. Heat the components from the table at a temperature of 110 °C until the mixture has completely melted.
2. Pour the remaining 7.2 kg of previously melted paraffin into the resulting mass.
3. Stir the mixture thoroughly and cool it to a working temperature of 80–85 °C before processing the scions.

An alternative protection method is using a bandage made of thin polyethylene film. A film sleeve 25–40 µm thick and 13–15 cm long is placed over the union site. Its width must correspond to the thickness of the grafted scion. Material consumption is 30–40 kg per 100 thousand grafted scions.

Scions with the sleeve applied are sent to a conveyor, where they are treated with a stream of hot air at a temperature of 350–400 °C in a heater. Under the influence of heat, the film shrinks and hermetically tightens the joint. The scion tissues themselves only heat up to a safe 36–38 °C, which does not harm the plant.

Applying the bandage and preparing grafts for planting

Bandaging with a film sleeve protects the scion-rootstock union site and creates optimal conditions for callus formation regardless of air humidity. The film retards bud development, and after it sprouts, the shoot enters the dry air of the stratification chamber immediately, which prevents mold infection. The technology allows for storing non-stratified grafts in refrigerators at a temperature of 2–6 °C for up to 1.5–2 months, significantly extending the grafting campaign period. At the same time, the formation of roots on the scion and the development of gray rot on the growth are completely excluded.

Sleeve assembly is performed on a special banding machine, to which a double-layer polyethylene film is fed. The scions are placed between the layers of film, after which the operator starts the mechanism's working unit by pressing a pedal. The entire process consists of several simple sequential actions:

1. Place the grafted cuttings between two layers of polyethylene film on the workbench.
2. Press the bandaging machine pedal to lower the pressure plate, which aligns both film sheets.
3. Trim and seal the film using an electrically heated chrome wire.

The finished sleeve should extend 1.5–2 cm beyond the tip of the scion. The bandaging wire is heated by a safe voltage ranging from 6 to 36 V. This technology is easily mechanized and does not require a major restructuring of the grafting complex's operations.

• Bandaging line productivity — 25,000–30,000 cuttings per shift
• Storage temperature before stratification — 2–6 °C
• Hardening period before planting — 5–6 days
• Temperature during hardening — 10–20 °C
• Air humidity during hardening — no more than 80%
• Diameter of the bandaging chrome wire — 0.4–0.5 mm

Thanks to the protective properties of the film, the grafts do not require long-term hardening before planting. It is sufficient to keep the cuttings for five to six days on a layer of damp sawdust under a canopy or film. Such material is planted in the nursery without hilling, which reduces manual labor costs. Furthermore, the bandage reliably protects the plants from damage by wireworms and cockchafer larvae, and also blocks the development of surface roots, eliminating the need for root pruning.

Modes and methods of stratification for grafted cuttings

Stratification is a mandatory preparation stage, during which callus forms on the cuts. Without this wound tissue, biological union of the lignified components is impossible. During stratification, cells differentiate, connecting cambial zones, vascular bundles, and other elements of the rootstock and scion. By the end of the process, the scion buds swell and begin to grow, and root primordia nodules appear on the heel of the rootstock.

For successful union, the cuttings are kept for 12–14 days in special chambers. They maintain a differentiated temperature regime: higher temperature in the graft zone and lower at the base of the rootstock, with high air humidity. In practice, two main methods of stratification are used, the choice of which depends on the technical equipment of the farm:

• with moisture-retaining material using general or local electric heating;
• without moisture-retaining material, using water or a nutrient solution in climate-controlled chambers.

For stratification with a moisture-retaining substrate, the grafted cuttings are placed in wooden slatted crates after waxing. Standard crate dimensions are 65–70 cm in length, 45–50 cm in width, and 60 cm in height. They are made using slats 5–7 cm wide and 1.5 cm thick. One of the side walls of the crate must be removable for ease of loading and unloading.

The cuttings are packed tightly, layered with damp, pre-steamed sawdust. One standard crate holds between 750 and 900 prepared grafted cuttings. Such packing ensures uniform heating of the graft zone and maintains the necessary level of humidity. This allows for obtaining a high-quality circular callus around the entire perimeter of the graft cut.

Substrate preparation and packing cuttings into crates

For graft stratification, sawdust from spruce, pine, linden, or alder is used. Before use, the substrate must be screened and steamed. This is necessary to destroy pathogens that cause rot in the callus and young shoots.

Sawdust steaming regime: in steam units at a temperature of 100–130 °C for 30 minutes, with the addition of chinozol at a rate of 100 g of the product per 1000 l of water. The humidity of the finished substrate should be 55–60% of the absolutely dry matter. You can check this by simply squeezing the sawdust in your fist — moisture should appear between the fingers, but not drip. A substrate that is too wet will block air access to the cuts, while one that is too dry will cause the cuttings to wither.

The grafted cuttings are packed in the following sequence:

1. Remove the side wall of the crate, place it on a rack with the open side facing up, and pour a 5–7 cm layer of prepared sawdust onto the bottom.
2. Carefully lay the grafted cuttings in a single layer, starting from the left and aligning their tops at the same level. Place the outermost cuttings 5–8 cm from the side walls of the crate.
3. Cover the laid row with a thin layer (3–5 cm) of damp sawdust. Repeat the procedure layer by layer.
4. When there is 5 cm left to the top edge of the crate, stop laying, fill the remaining space with sawdust, and slide the side wall back into place.
5. Place the crate vertically and cover the cuttings from above with a 7–8 cm layer of damp sawdust.

Each filled box must be labeled. It should indicate a number, which is also recorded in the logbook, the cultivars of the scion and rootstock, the number of grafts, and the date of placement. Additionally, the name of the grafter is recorded.

Stratification Regimes and Application of Local Electric Heating

After labeling, the boxes are moved to greenhouses, stratification chambers, or heated ventilated rooms. In the stratification zone, it is necessary to strictly maintain the specified microclimate parameters. Deviations from the recommended regime can lead to the death of the scions.

Parameter	Recommended value
Temperature in the graft union zone	24–26 °C
Temperature at the base of the rootstock	15–18 °C
Air humidity	85–90 %

The boxes are placed on shelves in one or two tiers. Every two days they are swapped: moved from the upper tier to the lower one, and from the lower to the upper. After 6–8 days, the boxes are lowered to the concrete floor to cool the bases of the cuttings to 15–16 °C. For this purpose, the floor is flooded with cold water so that it moistens the bottom part of the box by 5–6 cm, but does not come into direct contact with the bases of the rootstocks.

To prevent the development of mold, the room is ventilated 2–3 times a day for 10–15 minutes. If the top layer of sawdust dries out, it is replaced with a moister one. 2–3 days before the end of the process, the layer of sawdust over the cuttings is reduced by 3–4 cm to prevent shoot stretching.

A more technologically advanced method is stratification with local electric heating using UES–6 and ESU–2M units. Boxes with placed cuttings are arranged in a single row, covered from above with a layer of sawdust 7–8 cm thick, and covered with polyethylene film with a 10–12 cm overhang on the sides. Heating elements are placed on top, covered with film again, and filled with a 7–8 cm layer of dry sawdust for thermal insulation. If a heating mat with sewn-in elements is used, additional film is not required.

Control zone	Temperature during electric heating
Graft union zone	25–26 °C
Lower ends of the cuttings	15–16 °C

Such heating ensures uniform heat distribution in the graft union zone and reduces moisture loss. The process can be carried out even in unheated rooms or outdoors under a canopy in the spring. Local heating significantly increases the survival rate of grafts and the yield of ready-to-plant nursery plants from the nursery.

• Sawdust humidity during placement — 55–60%
• Stratification period — 14–16 days
• Readiness criterion (circular callus) — 70% of grafts
• Electric unit power — 2.5 kW
• Capacity of one unit — 72 boxes

The Moldavian Research Institute of Viticulture and Winemaking has developed a bulk method of stratification for grafted cuttings using a thermal screen, which is widely used in nursery farms in Moldova, Ukraine, and at the V. I. Lenin state farm in the Anapa district of the Krasnodar Territory of the RSFSR. This stratification method consists of placing the grafted cuttings not in stratification boxes, but horizontally in stacks with the scions facing inward.

The loading process includes the following stages:

• A thermal screen is installed between the stacks at a distance of 1.5–2 cm from the top of the grafted cuttings, ensuring a uniform temperature regime.
• The first row is placed on a 10–15 cm layer of moist sawdust; subsequent rows are layered with a 3–4 cm layer of sawdust.
• 6–7 thousand grafted cuttings are placed in 1 stack on each side of the screen.

In the room where the stratification of grafted cuttings using a thermal screen is carried out, the temperature is maintained at no higher than 15°C, and in the graft union zone — at a level of 24–26°C. At the same time, it is very important that the base of the rootstock does not dry out. This stratification method allows for the abandonment of boxes, reduces the farms' need for moisture-retaining material (sawdust) by half, increases the capacity of stratification rooms by 2–3 times, reduces electricity consumption by 30%, and significantly (by 60 man-days) reduces labor costs. Experimental studies by L. M. Maltabar (1983) showed the greatest efficiency of this method when stratifying grafted cuttings with a rootstock length of 100—17.0 cm for growing nursery plants with a ready-made trunk in non-covering viticulture regions.

Stratification of grafted cuttings in water. This method is the simplest and most accessible for all nursery farms, especially for those that do not have specially equipped chambers for stratification. It consists of the following. The tops of the grafted cuttings, carefully checked by an inspector, are waxed for 16–18 cm at a paraffin temperature of 100–105°C and ventilated until the bark dries. If the bark is not dried, a thick layer of waxed film forms on the grafted cuttings, which falls off, and the graft union becomes exposed. Then, the grafted cuttings are placed in boxes with wooden or metal pallets 1.6–1.8 m wide and 0.1–0.12 m high at the side. The length of the box can be arbitrary, depending on the length of the room chamber where the stratification will be carried out. The pallets have a slight slope for water drainage. The bottom and side walls of the pallets at a height of 10–12 cm are pre-lined with waterproof synthetic film. For better aeration of the rootstock base, a false bottom made of a wooden grate or slate sheets is set up at the bottom of the pallet at the water level. Grafted cuttings are placed on the bottom of the pallet so that the base of the rootstock touches the bottom.

Boxes filled with grafted cuttings are transferred to stratification chambers or regular greenhouses with general heating and set tightly together in a battery, placing up to 3,000 grafted cuttings per 1 m2 of usable area. The pallets of the boxes are filled with clean, warm, non-mineralized water or the nutrient solution by V. A. Chesnokov and E. N. Bazyrina so that the base of the rootstock heel is submerged in water by 3–5 cm. The battery of 12–16 boxes is covered from the top and sides with polyethylene film, arranged so that one side is slightly higher than the other, allowing droplets forming on the inner side of the film to run off without falling onto the grafted cuttings. Do not place boxes on a cement floor, as this causes water evaporation and cooling of the grafted cuttings. During stratification in chambers and other premises adapted for stratification, a constant temperature is maintained within 28–30°C and a relative humidity of the air" of at least 95%. Grafted cuttings are aired 1–2 times a day by removing the film from the boxes for 7–10 minutes. When the shoots reach 1.5–2 cm, the film is removed from the boxes to prevent rot on the young growth.

For prevention, as well as in the event of mold appearing on young shoots, the grafted cuttings are sprayed with a 0.1% solution of chinozol. To prevent shoots from stretching due to lack of light, they are supplemented with light (3000 lx) using DRL-400 lamps, placing one lamp for every 10 m2. The lamps are a source not only of light but also of heat, as well as ultraviolet radiation, which inhibits mold development.

During stratification, monitor to ensure that the water or nutrient solution in the containers with grafted cuttings is always at the same level, and that the temperature at the graft union is within 25–26°C, the water in the pallets is 23–24°C, and the irradiance is 40–50 W/m2 (12–14 hours per day). Under these conditions, stratification lasts 12–20 days, until 90–95% of the grafted cuttings in the union zone have formed a uniform, dense, greenish-white callus around the entire circumference and thick, unstretched sprouts with three to four leaves on the scion. Root primordia appear at the lower ends of the rootstock. In this state, the grafted cuttings are planted into the nursery immediately after stratification or 2–3 days later, which contributes to the preservation of nutrients in the cuttings and their good rooting.

Stratification of grafted cuttings without water-retaining material under conditions of intensive moisture: The method was developed by the K. A. Amiradjibi Georgian Research Institute of Mechanization and Electrification of Agriculture together with the Georgian Research Institute of Horticulture, Viticulture and Winemaking. The grafted cuttings are stratified in thermally insulated and moisture-proof premises—chambers constructed within greenhouses. The capacity of each chamber is up to 200,000 grafted cuttings. In each greenhouse, there are 6–10 windowless chambers, 10 m long, 6 m wide, and 4.5 m high. Three-tiered metal racks are placed in 2 rows in the chamber, set 0.9–1 m away from the walls, which facilitates the care of the grafted cuttings during their stratification and reduces the influence of temperature fluctuations from the chamber walls. A metal walkway with a stand is arranged between the rows of racks for placing grafted cuttings on the upper tiers.

T e c h n o l o g i c a l p r o c e s s A i r h u m i d i t y, % F i l l i n g t h e s t r a t i f i c a t i o n c h a m b e r w i t h g r a f t e d c u t t i n g s 9 0 – 9 3 I n i t i a l s t r a t i f i c a t i o n p e r i o d F i n a l s t r a t i f i c a t i o n p e r i o d 9 5 H a r d e n i n g o f g r a f t e d c u t t i n g s 9 0 – 9 2 U n l o a d i n g t h e c h a m b e r A c c l i m a t i z a t i o n o f g r a f t e d c u t t i n g s 8 8 – 9 0

Stratification and hardening regime for grafted cuttings under conditions of intensive moisture (according to Kuchava, 1976)

Under the chambers on the floor are metal tubs filled with water heated to 38–40°C using coils from an EPZ–100 type electric heater located in the greenhouse utility room. The chambers are saturated with humidity due to water evaporation from the tubs located under the shelving. The greenhouses are aerated using supply and exhaust ventilation systems. Air ducts for both systems are installed in each chamber. They are positioned so that fresh air is supplied to the chambers from the bottom up.

Immediately after grafting, the cuttings are necessarily waxed and placed vertically into frames—trays 65 cm long, 45 cm wide, and 30 cm high, made of 10 mm thick reinforcing iron. Their bottom is a low (3–5 cm) metal tray with holes for draining the accumulated water. Each such frame holds 1.5–1.6 thousand grafted cuttings. The frames filled with cuttings are transported along the paths and placed in the chambers on the shelving of all tiers, starting from the bottom one. In each chamber, the microclimate is automatically regulated in accordance with the parameters of temperature, humidity, aeration, and light required for the stratification of cuttings (see Table 5).

With this method of stratification, just as with water stratification, mold development is observed on the cuttings. To eliminate it, the chambers are aired more frequently, and centers of disease are washed off with a strong jet of water from a hose. The stratification of grafted cuttings and their hardening lasts up to 12–15 days. It is used in nursery farms in Georgia, Armenia, and the Crimean region of the Ukrainian SSR.

The method was proposed by the V. E. Tairov Ukrainian Research Institute of Viticulture and Winemaking. It is based on the principle of stratification of grafted grape cuttings in water under conditions of intensive air humidity with the automation of all production processes for grafted planting material. In this case, the grafted cuttings are also not layered with moisture-retaining substrate; their tops are intensively illuminated, and water or a hydroponic solution is supplied to the base of the rootstock (heel). The supply of conditioned air and the regulation of the set regime of temperature, humidity, and air aeration in the stratification chambers are automated.

The process of stratification of grafted cuttings using this method, according to V. G. Nikolenko (1980), takes place in 3 stages.

The duration of the first stage is 7 days, from placing the grafted cuttings into the trays until the buds swell and the first callus protuberances appear at the junction of the components. Environmental conditions:

• Air temperature at the graft union: 26–28°C.
• Temperature at the base of the rootstock (heel): 20–24°C.
• Relative air humidity: 100%.
• Irradiance: not less than 25–30 W/m² (14–16 hours per day).

During the first 2 days, the surface of the grafted cuttings must be moist. The water in the trays is changed daily. To avoid rotting of the grafted cuttings, the film is removed 4–6 times a day, and the room is aired for 3–4 minutes.

The duration of the second stage is 8 days. During this time, callus outgrowths appear on the grafted cuttings and the buds open. The temperature is maintained within the same limits, the air humidity is reduced to 90–88%, and the irradiance is increased to 50–70 W/m² (12–14 hours per day). It is not recommended to illuminate the grafted cuttings from 11 p.m. to 7 a.m. During this stage, the room is aired 8–10 times every 1.5–2 hours for 3–5 minutes. It is advisable to supply a hydroponic solution to the base of the rootstock every 3–4 hours for 3–5 minutes; its composition includes (g per 1 ton of water):

Potassium nitrate	500
Ammonium nitrate	200
Superphosphate	400
Magnesium sulfate	300
Ferric chloride	6
Boric acid	0.72
Manganese sulfate	0.45
Zinc sulfate	0.02
Copper sulfate	0.02

The second stage ends at the moment when 75–80% of the grafted cuttings have formed a circular callus outgrowth at the junction of the components at the base of the rootstock.

Finalization of stratification: third-phase regime and protection against rot

In the third stage of stratification, the physiological fusion of the grape graft components is completed. During this period, the outer callus outgrowths become suberized, a common vascular-conducting system is formed inside the graft union, and a shoot with two to three leaves develops on the scion. To ensure these processes are successful, it is necessary to transfer the grafts to a special light and temperature regime.

• Duration of the third stage — 5 days
• Scion temperature — 24–26 °C
• Rootstock temperature — 24 °C
• Irradiance of cuttings — from 90–100 W/m²
• Air humidity — 75–80%
• Total stratification period — 20 days

To prevent the appearance of mold, the air humidity in the room is reduced, and the chamber itself is aired every 1.5 hours for 6–8 minutes. At the same time, the hydroponic nutrient solution continues to be supplied to the base of the rootstock. The described technology ensures a high yield of high-quality grafts only when work is carried out during optimal calendar periods — from March 25 to April 25.