Stock and graft

After the phylloxera invasion, the roots of local vineyards were seriously damaged and it was necessary to consider reconstruction. Use was made of vines typical in phylloxera prone areas. If this pest came from North America, the solution also came from that country, where vines and disease live together in harmony. The European vines were reconstructed on an American root which was resistant to phylloxera; the upper part being capable of producing European grapes, the grape of the American vine is inappropiate. In this way, almost all existing vineyards have a "foot" or stock of the American vine with a graft of traditional vines from the Rioja.

Another circumstance influences the grafting operation. This involves a chemical reaction of the American vine root. This vine does not stand up as well as the European vine to the so-called active limestone in the soil, which in the Rioja can be plentiful.

Therefore, faced with the phylloxera attack, vinegrowers sought American vine roots resistant to the limestone present in their vineyards. But other factors, in addition to limestone, are taken into consideration when choosing a stock, such as:

• Depth of the arable soil
• Variety of European vine which is to be grafted
• Dryness of the area
• The desired production
• The salinity of the soil

What happens if the vinegrower does not graft? If the vinegrower plants a vine without grafting, he might do this with European vines which are susceptible to attack by phylloxera; their roots would not resist the attacks of this insect. Its productive life would only reach twenty years. But if he does not graft, we can also suppose he will plant American vines, in which case the vine lives a long time but produces inadequate grapes for wine-making. They will be rejected by the market due to a colour component called "malvina".

The European variety of vine, from which we obtain our wines has the scientific name of Vitis vinífera, while the American vines, from which come the phylloxera-resistant stocks, are of the following species:

Vitis rupestris, Vitis riparia, Vitis labrusca, Vitis berlandieri.

From experimental crosses of these American species, numerous stocks have developed. The most common of these, as used in the Rioja, are as follows:

Popular name	Origin of cross	Resistance to active limestone up to
3.309	Riparia x Rupestris	0-11%
Rupestris de Lot	Rupestris variedad of Lot	0-14%
99 R	(Richter) Berlandieri x Rupestris of Lot	0-17%
110 R	(Richter) Berlandieri x Rupestris	17%
161-49	Riparia x Berlandieri	0-25%
41-B	Chasselas (V. vinífera) x Berlandieri	0-50%

The grafting operation consists of joining recent cuts of the stock and graft. The cut is usually clean and oblique although it can be made with split mesh or with a scion. After a year in the soil, this grafting operation can be carried out where the stock is planted. This is the traditional system in La Rioja. In addition, it is possible to operate with the "taller" or "workshop" graft, this is the joining of the stock and graft in the nursery before planting in the vineyard. In this way a year is gained in the process of preparing the vineyard. Recently, the "pote" or "pot" system has been used, whereby grafts made in nurseries and rooted there are later transplanted to the vineyard with some earth which envelops the roots in a small perforated tub which afterwards decomposes in the soil.