The “dry-rot” wood decay fungus Meruliporia incrassata has recently attracted attention, primarily in the western coastal United States, as a particularly destructive pest of building material. Recently, the US Environmental Protection Agency (EPA) has accepted a voluntary withdrawal of the historically effective chromated-copper arsenate (CCA) as a preservative for wood used in residential settings. As the new generation of copper-based preservatives appear to be less effective against this fungus, it is becoming increasingly important to new countermeasures against M. incrassata. Oxalic acid and the oxalate-catabolizing enzyme, oxalate decarboxylase, are produced by all wood-decaying basidiomycetous fungi and have often been implicated in many aspects of the decay process. The purpose of this study was to gain a better understanding of the variability among different isolates of M. incrassata through the characterization of the oxalate/oxalate decarboxylase system. Four field isolates of M. incrassata obtained from wood in California were tested, as well as one ATCC isolate from Virginia, and one isolate of the similar European fungus Serpula lacrymans for comparison. All fungal isolates displayed a remarkably uniform production of both oxalate and oxalate decarboxylase, as well as a very rapid wood decay rate in standardized tests. The uniformity of this particular system may make it an effective target for non-specific preservatives; fungicides developed against this system have a greater chance of being more broadly effective across species and genera.

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