Browsing by Subject "Obstbau"

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    Feuerbrand : Charakterisierung und Bekämpfungsmaßnahmen
    (2012) Bantleon, Georg; Vögele, Ralf
    This work provides new scientific findings on control agents for fire blight after hail and during bloom, on fire blight susceptibility of modern apple cultivars and on fire blight pathogenesis of blossom infection and of internal stem movement. Experiments were conducted in the laboratory, greenhouse and field. Leaf damages after hail are points of entry for new infections. Until now, there has been no method established for testing control agents after hail injury. In the method developed, plants were damaged and sprayed with a suspension of Erwinia amylovora. Control agents were applied 4 h after inoculation. The visual symptoms were scored. Streptomycin showed high effectivity. Of 13 agents tested, 3 showed an effectivity sufficient for practical use (Juglon, LMA und Myco-Sin). Flowers are the main point of entry for Erwinia amylovora. Control agents for fire blight were tested according to EPPO standard PP 1/166(3). The goal was to identify alternatives to the antibiotic streptomycin which won?t be available in fruit-growing in the future. Out of 20 agents tested, streptomycin always showed high effectivity as well as spray strategies involving streptomycin. Three agents were found to be potential substitutes for streptomycin (Antinfek, Juglon und LMA). Eight modern apple cultivars were tested for their fire blight susceptibility in flower tests in the climate chamber and in the field. Rewena showed low, Mairac and Pinova medium, Diwa, Gala Greenstar and Kanzi high and Wellant very high susceptibility. The results of the climate chamber and results from field trials correspond. A clear relation between the density of the inoculation suspension and symptom development in flower and shoot was found in pathogenesis experiments. All concentrations led to infections. Higher concentrations led to more severe symptoms. In another pathogenesis experiment bacteria were injected into the stems of apple trees. Stem tissue was analyzed for Erwinia amylovora using real-time PCR. Bacteria could only be found below the point of injection what favors the idea of phloem migration.
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    Die Hypersensibilität der Europäischen Pflaume (Prunus domestica L.) gegenüber dem Scharkavirus (Plum pox virus)
    (2005) Neumüller, Michael; Wünsche, Jens Norbert
    In terms of economic damage, Sharka is the most important virus disease in stone fruit crops. The causative agent of this disease is the Plum pox virus (PPV). Some genotypes of European plum (Prunus domstica L.) show a hypersensitive response when infected with PPV. Results about the inheritance of this type of resistance mediated by hypersensitivity and different types of symptoms characteristic for the hypersensitive defence response in the interavtion PPV/Prunus domestica are presented. From the biochemichal point of view, it is shown that the defence response is indeed a hypersensitive response. A strategy for the development of DNA markers for hypersensitivity to PPV in European plum is developed. The potential use of hypersensitivity for solving the Sharka problem is discussed.