HISTOCHEMICAL ANALYSES OF SILICON-INDUCED RESISTANCE IN THE INTERACTION OF TOMATO (SOLANUM LYCOPERSICUM L.) AND RALSTONIA SOLANACEARUM. T. Schacht and K. Wydra.
Leibniz Universität Hannover, Institute of Plant Diseases and Plant Protection, Herrenhäuser Str. 2. 30149 Hannover, Germany. wydra@ipp.unihannover.de

Abstract: Silicon-induced resistance has been studied on molecular genetic and immuno-histochemical level and revealed an increase in expression of genes involved in the basal resistance reaction and of signalling genes belonging mainly to the jasmonic acid pathway. To further characterize and localize the reaction on histochemical level, various biochemical parameters linked to resistance in different pathosystems, such as tylosis formation, hydrogen peroxide accumulation, lignification and callose deposition were studied microscopically at different times after inoculation. Tomato genotype King Kong 2 showed significantly increased tylosis formation in vessels of the midstem in silicon-treated and R. solanacearum-inoculated plants compared to non-inoculated plants of the same treatment at eight days post inoculation (dpi), and an elevated tylosis formation compared to inoculated and noninoculated plants of the non-silicon treatment. At 12 dpi an increased tylosis formation was additionally observed in silicon-treated inoculated plants compared to all other treatments. Further investigations for differences in lignification, hydrogenperoxide accumulation and callose deposition revealed that these mechanisms are apparently not involved in the silicon-induced resistance of tomato to R. solanacearum.