The rootstock is an important factor for the control of the vigor and the balance between production and quality. It is not, however, the only factor that the winegrower may encounter. The density of the plantation, the system of irrigation and the force of the buds will interact with the rootstock. The level of mineral fertilization, as well as the watering, affect not only the vigor and production but also the quality.
To choose the rootstock correctly, you must take into consideration the following factors
— Spring frosts
• Soil characteristics
— Possible Phylloxera attack
— Presence of nematodes
— Active limestone and iron that can be assimilated
— Salinity of the soil and irrigation water (where relevant)
— Content of mineral elements
• Characteristics of the variety to be grafted
— Vegetative cycle and ripening season
— Productivity, quality of production and destination
• Conditions of cultivation
— Dry, watered or supporting irrigation
— Formation system
— Plantation structure
Considering all these factors, we must find the rootstock that best adapts to them.
In table number 1 we see the relation between the most important rootstocks and the main characteristics we should consider when making the choice.
We have seen that for the right choice of a rootstock, we have to take into account the climate, the soil type, the variety to be grafted and the system of cultivation.
The research on rootstocks conducted by the Departamento de Viticultura y Enología of CRIA and the viticulture experts of the OCAs cannot demonstrate conclusive results with the available data, since more years of production are needed. However, based on the these experiences and the results of other trials carried out in conditions similar to ours, we may reach conclusions about the rootstocks traditionally used in this region and other rootstocks that may be of interest:
• Rupestris Lot This has shown itself to be the most vigorous of all the rootstocks tested. In the trial, the rootstock with the Italia variety has been the least productive, giving loose bunches with less weight and an average grape size. Dominga, on the other hand, has been the most productive, with a larger size of both bunches and grapes, the highest sugar content and a compactness similar to the other standards. We do not believe it is advisable to use this rootstock in rainfed plantations because it has a low resistance to drought. However, irrigation should be used with caution, because the vigor of this rootstock is excessive and tends to cause coulure with most varieties.
• 41-B This is the rootstock with the lowest sugar content in all the trials, showing very compact bunches with reasonable colour, small grapes and little vigor. In production, it performed very well with the Italia variety but very poorly with Graciano. We recommend it in soils with a high risk of chlorosis.
• 161-49 This stock has adapted well in all the trials, and is most productive with the Graciano variety. It confers vigor to all the varieties, a good size of grape and an acceptable sugar content. It has a low resistance to drought and so is not suited to rainfed vineyards.
• 110-R This stock has had an acceptable performance in all the trials, both in production and in vigor, grape size, sugar content, colour and compactness of the bunches. We can say that it is a very safe rootstock, which is also, owing to its high drought resistance, adequate for rainfed vineyards.
• 1103-P This stock is very interesting, because of its great vigor, coupled with a high resistance to nematodes, salinity and drought. In the trial with the Italia vine we have seen that it performed very well over three years of production. In winemaking varieties, even though we lack our own data, we know that it is used in the South of Italy in conditions very similar to our own with good results. It should not be planted in soils with more that 17% of active limestone.
• 140-Ru This stock has very similar characteristics, but is more resistant to active limestone (20%). It may present problems of incompatibility with some varieties, although in the trials with Italia, Napoleón and Dominga grafts it has shown none so far.