METHODS IN SELECTION AND TESTING OF APPLE ROOTSTOCKS IN THE GDR

In apple rootstock breeding it is necessary to use effective early selection methods because of the long duration of the work in order to limit expenditure.

Analysing the selection sections

• testing of seedling plants

• stoolbed testing

• testing in the nursery

• testing in the field

we took into consideration all possibilities for the rootstoock breeding as well as for the breeding of apple varieties on national and international levels.

As seedlings the plants were tested for resistance to scab, fireblight and collar rot /artificial infection/. Stoolbed testing is connected with the examination of resistance to mildew and winter frosts.
Additionally it is possible to utilize the propagation of softwood cuttings as a broader base for tests in the norsery and in the field.

In the nursery the budded rootstocks are tested for graft compatibility and vigour by measuring the one year old trees.
The elimination effectivity of this method is about 70 %. At this stage the rootstocks are tested for natural infestation with woolly apple aphid.

At the stage of pomological testing with as little pruning as possible after 4 harvesting periods the evaluation of cropping capacity of rootstocks in combination with varieties is possible.
The most important criterion is the specific yield /kg/cm² cross-section surface of the stem or kg/m³ crown volume/ supported by the yield per tree and the vigour /crown volume or/and stem diameter/. Promising rootstock clones are quickly multiplied by in vitro propagation.

Fruit Breeding

M. Fischer

https://doi.org/10.17660/ActaHortic.1988.224.42