Propagation serves to spread and maintain species, vines and rootstocks over time. We can distinguish two propagation methods:
- Propagation by seed or gamic: limited today only to genetic improvement, it consists in the normal process of sexual reproduction which involves the sexual organs;
- Agamic propagation: the reproduction of the plant does not take place through the intervention of the sexual organs and clones are obtained, that is, of the plants genetically equal to the mother plant; there are various techniques of agamic reproduction (cutting, grafting ...).
Most European vines are not resistant to phylloxera attacks, therefore the propagation of these vines has long been linked to the use of the American foot graft.
Currently, the most requested material for the creation of new plants are grafted cuttings. They consist of a scion (that is, the part that will constitute the aerial apparatus of the plant) and a rootstock (the part of the plant that will constitute the root apparatus): it is therefore necessary to provide for the obtaining of wood to produce the rootstocks and the scions; then the grafting proceeds. Franks are also available on the market, that is, rooted rootstocks.
The propagation material, both for rootstocks and for scions, is placed on the market with an identification label, which contains the elements that identify the material and the producer (Marenghi, 2007). We distinguish three types of labels (Marenghi, 2007):
Bianca: "basic" category, material produced by the breeders or by the premultiplying nuclei, intended for nurserymen for the creation of mother plant fields, from which propagation material belonging to the "certified" category will be taken;
Azzurra: category "certified", ie produced by nurserymen for vine growers for the planting of vineyards, with guarantees on genetic origin and guarantees on health status;
Orange: standard category, or material without health guarantees; used for the multiplication of minor vines, for which clonal selections are not available.
The mother plants of the portinnessti can be raised on the ground or on supports no higher than one meter (rearing on the ground allows to avoid the inconvenience of the twisting of the shoots around the wires, as the shoots freely spread on the ground). The wood to produce the rootstocks is taken at the time of winter pruning (January-February): the shoots must be well formed and rich in starch; they are subsequently packaged in bundles of two to three meters in length and stored in an environment at controlled temperature and humidity (T = 2-3 ° C and R.H. 85%), avoiding their drying out and fungal attacks (Marenghi, 2007).
The wood for the scions is taken during the winter pruning from the mother plants and packaged and stored in the same way as the wood for the rootstocks. At the time of grafting, either for certified or standard material, a portion of wood of one year is taken, well lignified, with at least one intact gem and without vigorous female (Marenghi, 2007).
A few days before carrying out the grafting (March), the rootstock and scion grafts are brought to room temperature and partially immersed in water; subsequently the moon is operated by means of a table graft, generally of the omega type (there are also other types of graft, less used). At the level of the graft, waxes and paraffins are applied, in order to avoid perspiration, the ingress of light and pathogens (Marenghi, 2007).
Then follows the forcing phase, which is necessary to allow a good weld between the two blondes at the coupling point. The grafts-cutting are inserted in boxes and covered with sand or sawdust (the boxes are then placed in a position that respects the polarity of the plant). In the first two-days of forcing, the temperature goes from 20 ° C to 26-28 ° C, remains unchanged for about ten days and then gradually returns to 20 ° C; relative humidity always remains high (80%). At this stage, neither the release of roots nor the release of sprouts are important (Marenghi, 2007).
Once the forcing is finished and a selection of the best cuttings is made, the graft-cuttings are placed in the caterpillar in mid-April: a second waxing is necessary at the tip of the graft-cuttings to prevent dehydration. The cuttings remain in the cuttings throughout the season; once unpaved, the best sorting is carried out, the shoots are pruned (so as to leave only two buds) and the roots are reduced to 10-15 cm (to allow a better radical proliferation at the time of planting); a third waxing is also carried out, which protects them until commercialization and planting in the vineyard. The cuttings thus treated are grouped in bundles of 25, with folders and ready for marketing (Marenghi, 2007).
Example of grafted rooted vine (source: www.vivairauscedo.com)
Fact sheet by Enrico Ruzzene