Biodegradation of thujaplicins in living western red cedar

The role of three common fungal isolates from the heartwood of mature coastal western red cedar (Thujaplicata Donn) in the detoxification of thujaplicins was investigated. A Sporothrix species, Kirschsteiniellathujina (Peck) Pomerleau & Etheridge, and a Phialophora species are shown to form a succession of fungi, in that order, which invade red cedar heartwood from within and cause discolouration of the heartwood from light straw to red and various shades of brown. Thujin, a recently described lactone compound in red cedar heartwood extractives, is shown to be present in discoloured wood only. It is formed by the oxidative dimerization and isomerization of thujaplicins by the Sporothrix isolate. The other two fungi may play a minor role in thujaplicin degradation. Thujin is shown to lack toxicity to Poriarivulosa (B. & C.) Cooke, the common decay fungus of coastal western red cedar.