Resistance of a living organism against damage, in particular through infections and intoxications, but also environmental conditions (in contrast, immunity means a complete defense mechanism or insensitivity). In viticulture, there are four main points where (depending on location and climate ) a resistance of varieties are very important, that is mushrooms. frost. phylloxera and dryness (see under drought and water stress ). Often, in this context, the term tolerance is used instead. Plants often develop natural resistance to their enemies in very long periods of time to several millions of years, a good example is the resistance of certain American grape varieties to phylloxera, which is multi-stage, or against both species mildew, The picture shows the difference between a nonresistant and resistant vine when it comes to pruning a phylloxera sheet, Left a bag-like bile with therein phylloxera and eggs laid by it and on the right a weak reaction without bile formation. In extremely resistant vines occurs at a puncture no reaction at all.
On the one hand, resistance depends on whether pathogens like bacteria or virus, Poisons or even living things find the necessary living conditions, and on the other hand of defensive devices or by automatically taking place immediately after the infestation defense mechanisms of the organism concerned. It can be perfect or weak. Fungus tolerance refers to the fact that the fungal pathogen can multiply on the host plant, but does not or only slightly damages it. The cause is glucanases and chitinases These are parts of the complex defense mechanism of plants. They cleave the cell wall building blocks glucan and chitin, which occur in many fungal cell walls and inhibit or prevent thereby the mushroom growth. A similar effect have the so-called phytoalexins, which in infestation by microorganisms like mushrooms or bacteria are formed by the vine itself as a defense reaction.
In the breeding new grape varieties or documents Among other things, great value is attached to a high resistance to fungi and viral strains, to pests (especially in the case of rootstock grapevines phylloxera ) and frost resistance. The picture shows the difference between EU citizens, and Amerikanerrebe at the onset of a phylloxera at the root. In the completely resistant American vines no swelling ( Nodositäten or tuberosities ) and thus deprived of phylloxera food. Rather, a protective cork fabric is formed and thereby the penetration of moisture and microorganisms prevented.
Mushroom-resistant grape varieties are particularly in the Organic (organic) viticulture asked and become as PIWI varieties designated. New opportunities opened up Genetic Engineering, For example, successful trials were carried out, the variety Riesling to plant two genes of the barley and thus to confer fungal resistance. In addition to the large savings in Rebschutz expenditures by not necessary fight with pesticides and reduced working hours are the achievable positive environmental benefits to highlight. See also a complete listing of all pests and diseases below Vine enemies,
Sheet : By Joachim Schmid, Geisenheim - Self-photographed , CC BY 3.0 de , Link
Root : Von Abesadze, Makarevskaja and Zchakaja, Georgia 1930 - from Joachim Schmid, Frank Manty, Bettina Lindner: Geisenheim grape varieties and clones, Geisenheimer Berichte 67, 2009, ISBN 978-3-934742-56-7 , GFDL 1.2 , Link and Link