Soluble and cell wall-bound phenolics and lignin in Ascocalyx abietina infected Norway spruces

This study was conducted to identify the defence-related alterations in phenylpropanoid pathway in Norway spruce trees naturally infected with Ascocalyx abietina (Lagerberg). The results show differences in accumulation of soluble and cell wall-bound phenolics, contents of lignin and total peroxidase activities in the bark collected from three distinct regions of infected branches. The sites of the A. abietina infection, the browning reaction zones, were characterised by significantly higher levels of free and cell wall-bound phenolic acids, higher amount of lignin and lower peroxidase activities when compared with zones localised 20–30 mm from the margin of browning area and regions of infected branches that were not in contact with the pathogen. On the rise of phenolic contents in the reaction zones participated predominately derivatives of cinnamic acid, in particular p-coumaric acid, content of which increased by about 2.3- and 3.0-fold compared to the controls grown on two different stands in Karlův vrch and Velká Deštná. Pronounced accumulation of ester- and glycoside-bound benzoic acid derivatives (namely p-hydroxybenzoic and protocatechuic acids) was observed in regions of infected branches that were not in contact with the pathogen. The induction of biochemical response in these healthy looking zones of branches from infected trees might represent a systemic induction of phenylpropanoid accumulation in A. abietina infected Norway spruces.