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 a natural resistance to their enemies in very long periods to several millions of years, a good example is the resistance of certain American grape varieties against phylloxera, which is multi-stage, or against both types of mildew,
On the one hand, resistance depends on whether or not pathogens are involved 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 are found in many fungal cell walls and inhibit or inhibit fungal growth. A similar effect have the so-called phytoalexins, which in infestation by microorganisms how 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. Mushroom-resistant grape varieties are particularly in the Organic (organic) viticulture asked and are considered PIWI varieties designated. New possibilities are opening 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 emphasize. See also a complete listing of all pests and diseases below Vine enemies,