Choice of rootstocks

(especially against soil-borne pathogens)

Grafting, i.e. grafting a susceptible scion of the desired cultivar, onto a resistant or a robust rootstock (e.g. wild form), increases the resistance of the cultivar. The choice of rootstock balances soil type (lime intolerance of the scion, pH requirements), water demand, vigor and stability, and controls budbreak (early/late). In orchards and vineyards, in particular, less vigorous varieties are desirable because they provide better aeration and thus lower susceptibility to fungi even with less foliage work.

In fruit growing, standard rootstocks are available against various diseases:

• M9 and Genovese in pome fruit against fire blight.
• Docera 6, a hypersensitive rootstock in stone fruit. In plum, enhanced resistance to scab is achieved in combination with scab-resistant varieties.

In addition, in orchards, intermediate grafting is possible with trunk formers to 60-70 cm height. In currant, tall stems are grafted onto Ribes aurorum to obtain upright, stable stems that promote faster drying of leaves and fruit.

The former standard rootstock St. Julian GF6 552, since organic farming and ESFY (European Stone Fruit Yellows) is occurring, is no longer used because it develops stem shoots. This is a disadvantage in the transmission of ESFY by leaf suckers, which suck especially on stem shoots.

If the scion is susceptible to soil-borne pathogens and grows poorly, the use of an insusceptible rootstock variety is recommended (tomato on potato rootstock; cucumber and melon on pumpkin rootstock against Fusarium, Verticillium).