Quantitative analyses of distribution of the heart rot fungus Serpula himantioides in living Chamaecyparis pisifera using real-time polymerase chain reaction

Serpula himantioides is a widely distributed wood rot fungus that causes heart rot in various tree species. In Japan, heart rot associated with S. himantioides occurs in Chamaecyparis pisifera; however, its distribution within living trees and changes in its abundance as decay progresses remain unclear. In this study, we used a real-time polymerase chain reaction (real-time PCR) assay to specifically detect and quantify S. himantioides in wood. This allowed us to determine the distribution of S. himantioides in living C. pisifera and to monitor changes in its abundance as decay progressed. In addition, the mode of decay progression was characterized using nonhierarchical clustering. Serpula himantioides was detected from both decayed and undecayed heartwood and at sites as high as 12 m in the trunk, suggesting that it was widely distributed in the heartwood. The clustering analysis grouped samples into three clusters corresponding to the incipient, intermediate and advanced stages of decay. The abundance of S. himantioides increased from the incipient stage to the intermediate stage of decay and decreased at the advanced stage. The results quantitatively showed that intermediate stage decay moved up the trunk and replaced the part corresponding to the incipient stage as decay progressed. These results will be useful for devising methods for the early detection of heart rot caused by S. himantioides and to understand the progress of decay caused by wood rot fungi in living trees.