The vine that produces the grapes, whether it comes from clonal or massal selection, is referred to as the scion. Because of the phylloxera root louse in the vast majority of the world’s vineyards, it has become necessary to graft this fruiting variety to a rootstock resistant to the pest. There are several types of grafts, but the essential distinction is between types of bench grafts, where the vines are done in the nursery during the winter and planted out in the spring, or the field grafts, which are done in the vineyard the year before. Field grafts are less expensive and quicker, but they are also less reliable.
Since grafting is necessary to combat phylloxera, it is important to choose the correct combination of rootstock and scion. There are considerations other than phylloxera resistance that help determine the proper match. Vigor is one important consideration, because some rootstocks tend to produce more foliage. This can shade the fruit, and draw the vine’s resources away from ripening the fruit, slowing the ripening process. Rupestris and 110R are examples of rootstocks with good phylloxera resistance but excessive vigor.
Tolerance of alkalinity in the soil is another factor. This is quite important in the vineyards of Champagne, because the chalk is very alkaline. Some rootstocks absorb iron less well in alkaline soils, interfering with the vines ability to conduct photosynthesis (an effect called chlorosis). Fercal 41B and 333 EM are resistant to this effect. Other varieties, such as 5 BB, are better adapted to heavy clay soils that can provide too much water to others. In spite of the largely positive benefits of widespread grafting, it has also led to increase in viral diseases (such as leaf roll virus).
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