Term for cancerous, scabby and elongated deformities (tuberous = tumor-like), the formation of which is affected by the phylloxera is induced on the old (2 to 3 year old) roots. You are against that Nodositäten (Knots only on young roots) much more dangerous. The tuberosity penetrates the European grape varieties of the species Vitis vinifera (but not everyone else resistant Species) through the medullary canals of the root to the central vascular system. Either as a result of this or through later penetration of secondary pathogens such as bacteria or mushrooms the root is damaged so badly that it dies within one to two years from the point of infection. The result is a considerable reduction in the root mass and consequently a reduced one Nutrient- and water intake. In the early stages, this leads to growth of the ailments and later to death vine, Only a few vines can lead to dramatic damage in vineyards due to the devastating consequences of this infestation.
By the rebel-tolerant, American species Vitis cinerea var. Helleri (Vitis berlandieri), Vitis riparia and Vitis rupestris Due to a closer arrangement of the medullary rays, descendant rootstocks do not penetrate as deep into the root, they remain more superficial and are also completely sealed off by the plant with a protective cork tissue. Since the growths to the central vascular system do not break out, or at most only in exceptional cases, the roots survive such an infection almost undamaged, and there are no dramatic consequences as with the European Vitis vinifera grape varieties. Many American wild forms and crosses between them are able to tolerate phylloxera very well. They are therefore preferred for the breeding of resistant ones documents used. Of Vitis cinerea and Vitis rotundifolia descendant varieties even have a perfect one resistance against both types of phylloxera-induced root growth.
The left picture shows a microscopic section through a phylloxera attack on an older one Europeans-Rebwurzel with tuberosity thereby formed, with a hole-like depression penetrating far into the interior of the root. The right picture shows a microscopic section through a tuberosity on one American vine, The phylloxera tapping point was sealed off by corking. The worldwide solution to phylloxera is that finishing practiced at an American lower part a European scion is grafted on.
Source: Phylloxera - WIKIPEDIA German edition
Root Reblice: By Joachim Schmid, Geisenheim, - Self-photographed, CC BY 3.0 de , Link 1 and Link 2
European and American vines: J. Schmid, F. Manty, B. Lindner, ISBN 978-3-934742-56-7 , GFDL 1.2 , Link 1 and Link 2
Tuberosities: LWG Bayern