Induced resistance of Norway spruce, variation of phenolic compounds and their effects on fungal pathogens

Three clones of Norway spruce (Picea abies) were studied for their response to mass-inoculation with the blue-stain fungus Ceratocystis polonica. The effect of different pretreatments (fungal inoculation and wounding) before mass-inoculation was investigated for their possible role in an acquired re sistance reaction. Pretreated trees showed enhanced resistance to the subse quent mass-inoculation relative to control trees that received no pretreatm ent. Furthermore, the fungal colonization of inoculated trees was less than that of wounded trees. The phenolic content of the bark, analysed by RP-HP LC, was compared in trees receiving different treatments. Trees inoculated with C. polonica had higher average concentration of (+)-catechin, taxifoli n and trans-resveratrol than wounded trees. Both inoculated and wounded tre es had higher average concentrations of these compounds than control trees. The effect of the phenolic extract of Norway spruce bark on the growth of the root rot fungus Heterobasidion annosum and the blue-stain fungi C, polo nica and Ophiostoma penicillatum were investigated in vitro. Heterobasidion annosum was not negatively affected, and the extracts had fungistatic effe cts on the blue-stain fungi. The growth of O. penicillatum was more inhibit ed than the growth of the more aggressive C. polonica.