Browsing by Subject "Induced systemic resistance"

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    Pathogenitätsfaktoren und induzierte Resistenz in der Interaktion von Orobanche ramosa L. und Nicotiana tabacum L.
    (2005) Gonsior, Guido; Sauerborn, Joachim
    Parasitic weeds of the genus Orobanche, cause severe damage to vegetables, legumes and sunflower in Europe, the Middle East and North Africa. Recently there is evidence for increasing occurrence of branched broomrape (Orobanche ramosa L.) in rape and tobacco cultivars in France and Germany. This research concerns on biology and pathogenicity of O. ramosa with special focus on the interactions with the host plant. In addition mechanisms of induced resistance of the host plant against the parasite were considered. The results showed genetic differences between the populations of O. ramosa in Germany, which partially parasitize different hosts. As possible factors of pathogenicity the accumulation of reactive oxygen species and a high peroxidase activity together with a high antioxidative capacity caused by the phenylpropanoids Verbascosid and Oraposid were identified. The control of branched broomrape was possible by application of agents, which are described to induce disease resistance. Control of branched broomrape could be based on systemic acquired resistance (SAR) as well as on induced systemic resistance (ISR). As defense mechanisms in tobacco roots against O. ramosa the biosynthesis of the hydroxycoumarin scopoletin and a significant increase of soluble and bound phenolics was discussed. This is underlined by a high activity and an increased expression of phenylalanine ammonia-lyase (PAL) the key enzyme of the phenylpropanoid pathway. Beside phytoalexin production we recognized an increased activity of peroxidases in Orobanche ramosa infected tobacco roots. Further it could be shown that the plant hormone Ethylene as well as the regulation of the sugar metabolism have importance for the resistance of the host plant.