Apparition de substances de type phenolamide lors de l'interaction Dianthus caryophyllus L. var. scania-Phytophthora parasitica dastur

Lorsque des sections basales de boutures d’oeillet (Dianthus caryophyllus L. var. « Scania ») deviennent résistantes à Phytophthora parasitica Dastur, il apparaît des substances très fluorescentes parmi lesquelles un groupe (taches chromatographiques 6-6’) semble plus spécifiquement marquer l’état de résistance lorsqu’elles s’accumulent considérablement in situ. Tous ces composés fluorescents ont une nature aminée et possèdent un spectre d’absorption ultra-violet de type hydroxycinnamique. Nous proposons que ces molécules nouvelles, de type phénolamides, puissent servir de marqueurs physiologiques chez l’oeillet, en particulier de la résistance à P. parasitica. Leur purification en vue d’une identification est en cours.Previous research on the resistance of carnation cuttings to Phytophthora parasitica Dastur has shown that a water-soluble elicitor from P. parasitica, can induce either resistance of the basal tissues of carnation (cuttings) or biosynthesis, in these tissues, of two fungitoxic phytoalexins. The present work was performed on three kinds of carnation cuttings (table 1) B.F. : freshly sectioned cuttings, B.R. : B.F. cuttings (rooting) in a perlite substrate for 7 days, B.E. : B.F. cuttings in an elicitor suspension (homogenized mycelium of P. parasitica carnation strain 26 in distilled water) for 24 hours. When Dianthus caryophyllus L. var. « Scania » becomes resistant to P. parasitica strain 26 (B.E.) we usually observe in the resistant tissues a number of new and highly fluorescent compounds (table 2 and fig. 1). These include a group of substances (chromatographic spots 6-6’) which are almost absent from B.R. cuttings, susceptible to P. parasitica carnation strain 26. Another group of substances (chromatographic spots 5-5’) always accumulates in B.R. cuttings (cf. table 2), and so are considered as good indicators of rhizogenesis. All these compounds have some of the properties of neutral phenolamides : U.V. spectra, amine constitution (table 3), solubility in organic solvent, fluorescence. The correlation between 6-6’ accumulation and resistance to P. parasitica carnation strain 26 (table 4) suggests that 6-6’ are directly involved in resistance in vivo. Purification of these compounds (for identification) is almost achieved and results will be given in a further communication