Name for cancerous, scurfy and elongated deformities (tuberous = tuberous), their formation in infestation by the phylloxera is induced on the old (2 to 3 year old) roots. They are opposite the Nodositäten (Knots only on young roots) much more dangerous. The tuberosities invade the European grape varieties of the species Vitis vinifera (but not everyone else either resistant Species) through the marrow channels of the root to the central vasculature. Either already by it or by later penetrating secondary exciters like bacteria or mushrooms The root is so severely damaged that it dies within one to two years from the point of infestation. The consequence is a considerable reduction of the root mass and consequently a diminished one Nutrient- and water intake. This leads in the initial stage to stunted growth and later to the death of the vine, Already few phylloxera can cause dramatic damage in vineyards because of the devastating consequences of this infestation.
By the rebel tolerant, American species Vitis cinerea var. Helleri (Vitis berlandieri), Vitis riparia and Vitis rupestris As a result of a narrower arrangement of the medullary rays, the tuberosities do not penetrate so deeply into the root, they remain more superficial and are completely sealed off by the plant by a protective cork tissue. Since there is no or at most in exceptional cases to break through the growths to the central vascular system, the roots survive such an attack almost unscathed, and there are no dramatic consequences as in the European Vitis vinifera grape varieties. Many American wild species and crosses between them are thus able to tolerate phylloxera infection very well. They are therefore preferred for the breeding of resistant documents used. From Vitis cinerea and Vitis rotundifolia descending varieties even have a perfect one resistance against both types of red blood-induced root proliferations.
The left picture shows a microscopic section of a phylloxera sting on an older one Europeans-Rebwurzel with tuberosity formed thereby, with a hole-like depression penetrating far into the interior of the root. The right image shows a microscopic section through a tuberosity on one American vine, The Anstichstelle the phylloxera was sealed off by Korkgewebebildung. As a solution against phylloxera today is the world finishing practiced while on an american lower part a European scion grafted on.
Source: phylloxera - WIKIPEDIA German edition
Root phylloxera: 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 Bavaria