P. Burmeister
It was possible to determine proliferation disease with some reliability in artificially infected apple rootstocks-mother plants by grafting strong layers of the infected stocks to the indicator Golden Delicious one year after the inoculation, and placing them in the greenhouse. When used, weaker layers tended to die before developing symptoms of proliferation; when stronger material was used, approximately 73% of the plants developed definite symptoms of proliferation, about 7% of the plants died.

When rooted layers of mother plants and the layer - indicator combination were sectioned into scions from base to tip, and each scion was grafted with the indicator Golden Delicious, in order to determine in which parts of the plant the disease could be detected, the results were inconsistent. In the case of the layers, sometimes only the root part developed symptoms, and otherwise the disease could be detected even in areas above the mid-section of the sectioned shoot. However, even four years after the infection of the mother plants, the disease could not be detected in all layers.

In some plants it was possible to detect proliferation in almost all sections from base to tip by indexing the rootstock - indicator combination.

Burmeister, P. (1976). INDEXING FOR APPLE PROLIFERATION IN ROOTSTOCKS. Acta Hortic. 67, 279-286
DOI: 10.17660/ActaHortic.1976.67.37

Acta Horticulturae