Combination of non-specific DNA amplification by Phi29 DNA polymerase and specific amplification of the internal transcribed spacer(ITS)regions of ribosomal DNA(rDNA)by polymerase chain reaction(PCR)is a useful method to identify basidiomycotal species inhabiting in decayed wood. In this study, we examined these DNA amplification conditions for quantitative assessment of basidiomycotal flora. DNA samples from the white-rot fungus Phanerochaete chrysosporium and the brown-rot fungus Postia placenta were equally mixed and subjected to the combined DNA amplification under various conditions. The ratio of DNA from the two species retained almost the original level during non-specific DNA amplification by Phi29 DNA polymerase. On the other hand, increase of PCR cycles caused to bias the ratio of DNA from the two species. On the basis of these results, to conduct quantitative assessment of basidiomycotal flora, the number of PCR cycles should be minimized within the exponential phase of amplification.

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