Ph.D. Dissertation

Characterization of Fungal Communities in Selected Wood Species by Field Exposure Tests

Advisors: Jeff Morrell and Jeff Stone.

Fungi are the primary biological agents of wood deterioration and cause major economic losses of wood products globally. Wood in outdoor applications tends to remain wet for extended time periods, making it susceptible to fungal attack. Understanding the factors involved in fungal colonization of wood is important for developing improved methods for preventing decay, but the process is complicated. Several fungal species can occur simultaneously on the substrate, and many of these fungi cannot be isolated by traditional culturing methods. There is the need to use multiple approaches to study fungal communities in exposure conditions that simulate real life scenarios.

In this study, fungal communities colonizing red alder, Douglas-fir and western red cedar exposed in stake and lap-joint field tests were characterized at the early stages of exposure. Samples installed at the Starker Post Farm (Corvallis, Oregon, USA) were collected at various time points over a two-year period. Fungal identification was conducted using culture-based isolation followed by sequencing of the Internal Transcribed Spacer (ITS) region of ribosomal DNA of the isolated fungi, and culture-independent high-throughput Illumina sequencing of the ITS of rDNA. Combinations of approaches including identification techniques, wood types, exposure conditions, and time points increased the ability to detect greater diversity of fungal communities colonizing wood in outdoor conditions.

Dissertation Chapters:

1. INCIDENCE OF FUNGAL COLONIZATION ON UNTREATED WOOD IN ABOVE-GROUND EXPOSURE USING A LAP-JOINT TEST.

2. FUNGAL COLONIZATION OF WOOD IN GROUND CONTACT EXPOSURE DETERMINED BY CULTURE-DEPENDENT METHODS.

3. DIVERSITY OF WOOD-INHABITING FUNGI IN GROUND CONTACT EXPOSURE DETERMINED BY ILLUMINA SEQUENCING.

4. COMPARISON BETWEEN HIGH-THROUGHPUT-ILLUMINA SEQUENCING AND CULTURE-BASED ITS rDNA.