Zur Auswirkung von Resistenzreaktionen auf Pflanzenwachstum und Ertrag in inkompatiblen Wirt‐Parasit‐Systemen

Effects of defense reactions on plant growth and yield in incompatible host‐parasite‐systems Investigations in incompatible host‐parasite‐systems (barley – Erysiphe graminis and lettuce – Bremia lactucae ) were carried out to prove, whether the induction of defense reactions leads to measurable effects on the yield performance of plants. Permanent or frequent inoculations with avirulent races decreased yield of barley and lettuce remarkably, expressed in reduced fresh weight and drym, atter. Less grains were produced and their contents of carbohydrates and amino acids were diminished significantly. In young plants a reduction in sugar content was evident already after a single inoculation. In barley as in lettuce this effect was shown, not only for inoculated, but also for plant parts not present at the time of inoculation. There, in addition especially aromatic amino acids increased, while glutamate, aspartate and their amides diminished. The consequences of a permanent maintenance of postinfectional resistance mechanisms either of a hypersensitive or non‐hypersensitive reaction type for growth and yield performance are discussed with regard to an increased consumption of energy and carbohydrates.