PHENOLIC-COMPOUNDS HISTOLOCALISATION IN P LANT-PARASITE INTERACTIONS IN SUNFLOWER AND GRAPEVINE

Some phenolic compounds were studied histochemically before and after infection during two kinds of interactions : Helianthus resinosus / Sc lerotinia sclerotiorum and Vitis spp. / Plasmopara viticola. H. resino sus is a wild sunflower species chosen for its high tolerance to S. sc lerotiorum. For grapevine, three species of different susceptibilities were analysed. Microscopical observations after marking of cross-sect ions by different coloured or fluorescent probes showed presence of ph enolic compounds pre-existent to infection in resistant species (hydro xycinnamic and gallic derivatives). After infection occured accumulati on of different phenolic compounds, (caffeic derivatives and flavonoid s) more rapidly in resistant species which certainly avoid parasite ex tension.