Induced resistance: criteria, mechanisms, practical application and estimation
1993
Schoenbeck, F. (Hannover Univ. (Germany). Inst. fuer Pflanzenkrankheiten und Pflanzenschutz) | Steiner, U. | Kraska, T.
Conceptually, induced resistance describes the improvement of natural resistance of a plant without alterations of the genom. This definition includes besides efficacy on the reduction of parasite infestation the yield response of the plants, meaning that induced resistance may not only reduce disease incidence, but additionally the damaging impact of the remaining pathogens on plant yield. The following criteria contribute to the verification of induced resistance: absence of toxic effects of the inducing agents to the parasite, necessity of a time interval between application of the inducers and the onset of effects in the plant, suppression by specific inhibitors affecting the gene expression of the plant, and the absence of a significant dosage-response correlation. Examples of different methods of induction with different plant and fungus species illustrate the considerable potential of induced resistance, regarding both, the efficiency of disease control and yield increase. The basic mechanisms leading to the effects observed have not been investigated to a satisfactory extent, although the following more or less well founded hypotheses are being discussed: the existence of a sequence of signals, alterations in gene regulation and expression as well as in enzyme activities, cell wall modifications, an impaired fungal nutrition, and altered sink-source relationships. Finally, the induced resistance is evaluated regarding the possibilities of application in practical plant protection
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