The influence of preformed defences on the dynamic wound response in Spruce bark

1. Two of the principal defences in conifer bark against attack by bark beetles and associated fungi, the flow of preformed resin and the dynamic wound response (DWR), are commonly regarded as separate, sequential responses to attack. In this paper the concentration of three preformed defences (resin, total polyphenols and lignified stone cell masses) was measured at different heights on the stem of Norway and Sitka Spruce to determine their effect on the size of lesions formed during the DWR to inoculation with three facultatively pathogenic fungi ( Phacidium coniferarum, Ophiostoma piceae and Cryptosporiopsis sp.) inoculated during the dormant season.
2. There was considerable within-tree variation in concentration of lignin and there was a dose-dependent negative effect of lignin on lesion size. The form of the relationship, however, was influenced by fungal and tree species and for some fungi, also by an individual tree effect.
3. Results suggest that resistance of conifer bark to pests and pathogens depends on an interaction between preformed and induced defences.