Comparison of general fungal and basidiomycete-specific ITS primers for identification of wood decay fungi

The identity of the fungi associated with and responsible for wood decay could lead to the development of more environmentally benign wood preservative systems. In this study we have reconstructed the phylogenetic tree of a select group of basidiomycete fungi using nucleotide sequences of the internal transcribed spacer (ITS) region. We then compared this to trees generated from restriction fragment length polymorphism (RFLP) analysis using two different primers to see if the latter procedures can correctly identify multiple isolates of select wood decay fungi. The phylogenetic tree using maximum likelihood analysis revealed three well-supported genera, Trametes, Phanerochaete, and Gloeophyllum, with bootstrap values of 75 or greater. Trametes and Phanerochaete were sister taxa, and Gloeophyllum was a sister taxon to the Trametes/Phanerochaete clade. Neither set of RFLP data could resolve the three genera into monophyletic groups. The RFLP tree based on general fungal primers also did not resolve species, while the basidiomycete-specific data could resolve species. In the basidiomycete-specific tree, all isolates of both G. striatum and G. trabeum comprised monophyletic groups. Eight of nine T. versicolor isolates, 10 of 11 G. sepiarium isolates, and nine of 10 T. hirsuta isolates comprised monophyletic groups. Phanerochaete could not be consistently resolved into monophyletic groups at either the generic or specific level. Our studies indicate that RFLP analysis using general fungal primers are not likely to be useful in identifying species or reconstructing phylogenetic relationships. RFLP analysis using basidiomycete-specific primers may be useful in identifying some species but not in reconstructing phylogenetic relationships although it is a simpler procedure than sequencing. More than 95 percent of the 1.5 million homes constructed in the United States each year are framed with wood (Smith and Wu 2005) and wood composite panels, such as OSB and plywood, which are the most common wall siding materials. Wood frequently exposed to moisture will be degraded by insects and microorganisms, thereby losing its strength and ability to serve as a construction material. In the United States, homeowners spend more than 5 billion dollars annually in replacement costs not including labor (Dost and Botsai 1990). Traditional methods to protect wood from decay have focused on the use of chemical preservatives as nonspecific, broad spectrum pesticides (Eaton and Hale 1993). Effective wood preservatives often generate environmental concerns, and many have been banned or their use restricted after they have been in service for a number of years because of unintended consequences to nontarget organisms, including humans. Wood preservatives that affect only organisms responsible for wood decay have the potential to be both more environmentally innocuous and effective in the long run. Basidiomycete fungi are the principle microbial decomposers of The authors are, respectively, Assistant Research Professor and Associate Professor, Dept. of Forest Products, Mississippi State Univ., Mississippi State, Mississippi ([email protected]; [email protected]); Assistant Professor, Kennesaw State Univ., Kennesaw, Georgia ([email protected]); and Professor, Mississippi State Univ., Mississippi State, Mississippi ([email protected]). This work was funded by grants from the USDA/Wood Utilization Research and the Life Sciences and Biotechnology Inst. (LSBI) Mississippi State Univ. This paper has been approved as FWRC 404. This paper was received for publication in February 2007. Article No. 10312. ✳Forest Products Society Member. ©Forest Products Society 2008. Forest Prod. J. 58(4):66-71.