PHENOLIC PREDICTORS FOR NORWAY SPRUCE RESISTANCE TO THE BARK BEETLE IPS-TYPOGRAPHUS (COLEOPTERA, SCOLYTIDAE) AND AN ASSOCIATED FUNGUS, CERATOCYSTIS-POLONICA

Changes in phloem phenolic content of Norway spruce (Picea abies (L.) Karst.) clones were followed during the first 12 days of the reaction induced by phloem artificial inoculation with Ceratocystis polonica Si em., a bark beetle (Ips typographus L.) associated fungus. The aim was to confirm our previous results concerning the mechanisms of this rea ction and the possible predictors of Norway spruce resistance to bark beetles and their associated fungi. The induced reaction was character ized by a slight decrease of tanning ability and an increase of (+)-ca techin concentration, which confirmed our previous observations. The r elative resistance of the clones was first predicted using the predict ors previously proposed. In addition, the first axis of the principal component analysis describing the phenolic content of all clones was u sed as a synthetic predictor (resistance axis). Related variables were also tested as predictors. Actual resistance of each clone was then m easured, using mass inoculations of C. polonica, and was compared with the predictions. Four predictors were so validated: the resistance ax is, tanning ability and isorhapontin concentration in uninoculated phl oem, and (+)-catechin concentration in the phloem 6 days after its ino culation. Phloem phenolic composition could thus be used to predict No rway spruce resistance to bark beetles and their associated fungi.