PHENOTYPIC AND BIOCHEMICAL ANALYSES OF SILICON – INDUCED RESISTANCE AGAINST RALSTONIA SOLANACEARUM IN POTATO GENOTYPES. D. Sadikaj and K. Wydra Institute of Plant Diseases and Plant Protection, Leibniz Universität Hannover, Herrenhäuser Str. 2, 30419 Hannover, Germany. wydra@ipp.uni-hannover.de

Abstract: Treatment of potato genotypes Desirée, moderately resistant, Saxon, susceptible, and Estima, highly susceptible to bacterial wilt, with silicon identified potato as Si-non-accumulator (less than 0.13% Si in roots). Silicon treatment in form of monosilicic acid and silicon dioxide reduced disease severity and incidence in genotype Desirée by 35% and 25%, respectively, while for genotype Saxon the influence of silicon was variable, and no effect was observed in Estima. Silicon amendment reduced the colonisation of roots and stems in the three genotypes. No significant differences in PAL activity and soluble phenols were found across treatments in genotypes Desirée and Saxon. In genotype Saxon PAL activity was tendenciously suppressed in the Rastonia solanacearum infected plants, regardless of the Si amendment and plant organ tested, root or stem. No significant differences were found between treatments and genotypes in PAL activity and total soluble phenols. Probing cell walls of mid-stem xylem vessels with the anti-arabinogalactan protein (AGP) antibody LM2 revealed higher accumulation of AGPs due to R. solanacearum infection in genotype Desirée. The induction was stronger in the R. solanacearum-infected, siliconamended treatment, whereas un-inoculated treatments showed no increased fluorescence. No differences were found in genotypes Saxon and Estima. The results of this study indicate that Si nutrition can induce resistance mechanism in a non-accumulator plant species, in a genotype-dependent interaction, as we similarly observed in here not presented studies with eggplant and geranium.