Plant-fungal mycorrhizal symbioses play an important role in the health of forest trees and the functioning of forest communities and ecosystems. Tree species composing the forest community shift through time, and along with them, their mycorrhizal fungal symbionts. Therefore, understanding the makeup of both the tree and fungal members of a community can be important in understanding forest succession. The focus of my research is the eastern hemlock (Tsuga canadensis), a foundation tree species of our eastern forests that is presently experiencing a range reduction due to insect herbivory and climate warming. My hypothesis is that remaining hemlock trees will associate with a somewhat altered mycorrhizal fungal community due to isolation in predominantly oak hardwood forests, and that this will have a bearing on the health of the trees.
Figure 1-Locations for rDNA and cDNA primers (a and b), primer sequences and amplicon lengths (c) and a photomicrograph of a mycorrhizal root tip (d).
Figure 2-2% agarose gel of DNA amplified from four hemlock root tips (1-4) and two different species of oak (5 and 6). Actual length of tree cDNA amplicons are in parentheses along with the common names.
Figure 3-2% agarose gel of both plant and fungal DNA amplified from single root tips of seven known potted trees. Double bands were excised and separated for sequencing. Actual length of tree cDNA amplicons are in parentheses along with the common names.
Both aims of this study were achieved. First, tree and fungal species were identified using DNA sequencing and comparison with published GenBank sequences. Sequence homologies were 100% for the plant species (except for Quercus prinus (97%), which is not yet in GenBank), and 95-100% for the various fungal species. Second, hemlock DNA bands can be easily distinguished from oak, birch and beech bands by their greater migration distance on a gel (figures 2 and 3). The technique presented here can conceivably be adapted to any target species or forest community.
I would like to thank Dr. Berish Rubin for his insight and guidance, and for keeping the project focused. I would like to offer extra special thanks to Bo Liu and Leleesha Samaraweera, who made themselves available for countless questions, kept me supplied with necessary materials and gave much valuable advice.
|This document was last modified 05/11/2009.|
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