Testing the systemic induced resistance hypothesis with Austrian pine and Diplodia sapinea

Systemic induction of defenses (e.g. phenolic metabolites) is considered vital in conifer resistance to pathogens and insects, and forms the mechanistic basis of the systemic induced resistance hypothesis (SIRH). In this study, the SIRH was tested on juvenile Austrian pine. Main stems expressed SIR in a manner that was consistent with the SIRH, while shoots became uniformly more susceptible to subsequent inoculations, demonstrating clear organ specificity in the tree's response. The majority of phenolic metabolites were poorly correlated with phenotype. Thus, the defensive system of Austrian pine is highly plastic and organ specific, and cannot be predicted by phenolic profiles alone.