Changes in phenolic metabolites of Scots‐pine phloem induced by <i>Ophiostoma brunneo‐ciliatum,</i> a bark‐beetle‐associated fungus

Abstract

Summary Changes in soluble phenol contents of Scots‐pine ( Pinus sylvestris ) phloem were studied after inoculation with Ophiostoma brunneo‐ciliatum , a fungus associated with Ips sexdentatus . They were compared to the length of the fungus‐induced reaction zone of the phloem, taken as an estimation for the trees' response efficiency against aggression. Five clones consisting of 14 trees were studied, and eight soluble phenolic metabolites were analysed in detail in reaction zones and in unwounded phloem sampled 3 weeks after inoculation. The stilbenes pinosylvin and pinosylvin monomethylether, and the flavonoid pinocembrin, were detected in reaction zones only. Concentrations of two p‐coumaric‐acid esters and an acetophenone glycoside decreased after inoculation. Variations of the flavonoids taxifolin and 3' taxifolin glucoside were inconsistent. One tree had longer reaction zones and a phenolic content different from the others. In unwounded phloem, concentrations of some phenolic compounds and in particular the ratio between the two p‐coumaric‐acid esters could be markers for trees' response efficiency. In the reaction zone, markers could be the ratios between concentrations of certain preformed compounds and concentrations of newly synthesized pinosylvin and pinocembrin.