Contribution to the mode of action of aluminium ethyl posphite in the parasite-host-interaction Bremia lactucae-lettuce
1986
Dercks, W. (Bonn Univ. (Germany, F.R.). Inst. fuer Pflanzenkrankheiten) | Buchenauer, H. | Crueger, G.
German. In greenhouse studies 5000 mg per kg aluminium ethyl phosphite exhibited a high preventive and curative effect against Bremia lactucae in lettuce plants. It could be shown that timely curative treatments with the fungicide can yield better results than preventive routine applications. It could be demonstrated that intercellular fluids obtained from fungicide-treated plants reduced distinctly the germination of Bremia lactucae conidia in vitro. The existence of a phenomenon in lettuce was found which could be interpreted as induced resistance. This appeared independently of treatment with aluminium ethyl phosphite. The chemical had an immediate influence on pathogenesis of Bremia lactucae; growth respectively development of all fungal organs and structures (germination, germ tube, appressorium, primary and secondary visicle, intercellular mycelium, haustoria) was prevented or inhibited dependent on application time of 5000 mg per kg, the concentration used for control of lettuce mildew in practical horticulture. Thus, the effect was at least partly direct and not specific concerning certain stages of the infection process. It could be demonstrated that the substance glyphosate and alpha-aminooxyacetic acid affected the expression of symptoms and did not counteract the fungicidal effect of aluminium ethyl phosphite; alpha-aminooxyacetic acid acted even fungitoxic itself. The results of the investigations indicate that a stimulation of natural defence mechanisms in plants is the consequence or a side effect and not the cause of the fungicidal efficiency of aluminium ethyl phosphite
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