INDUCED RESPONSES IN PHENOLIC METABOLISM IN 2 NORWAY SPRUCE CLONES AFTER WOUNDING AND INOCULATIONS WITH OPHIOSTOMA-POLONICUM, A BARK BEETLE-ASSOCIATED FUNGUS

Two Norway spruce (Picea abies Karst.) clones, one resistant and the o ther susceptible to mass inoculation with Ophiostoma polonicum Siem., were compared with regard to their phenolic compositions and chalcone synthase (CHS) and stilbene synthase activities of their phloem before and at 6 and 12 d after artificial inoculation with sterile malt agar or O. polonicum. In unwounded phloem, the resistant clone differed fr om the susceptible clone by the presence of taxifolin glycoside, lower concentrations of stilbene glycosides, and higher CHS activity. After inoculation, (+)-catechin concentration and CHS activity dramatically increased around the wound, particularly in the resistant clone. Stil bene synthase activity also increased, but more slowly and to a lower level, whereas the concentrations of stilbenes remained stable. Tannin g ability decreased in the susceptible done, whereas it remained stabl e in the resistant one. It is proposed that the induced phenolic respo nse of Norway spruce phloem consists of an activation of the phenolic pathway, finally leading to tannins and insoluble polymers. It is sugg ested that resistance to O. polonicum depends on the ability of the tr ee to easily activate the flavonoid pathway.