Date of Graduation

Spring 5-11-2019

Document Type

Thesis

Degree Name

Master of Science in Biology

College/School

College of Arts and Sciences

Department/Program

Biology

First Advisor

Dr. Naupaka Zimmerman

Second Advisor

Dr. Jen Dever

Third Advisor

Dr. John Paul

Abstract

Endophytes are microbes that live within plants without causing detectable illness. These microorganisms can emit volatile organic compounds (VOCs), airborne signaling molecules that can significantly affect plant growth. Despite the prevalence of endophytes and their VOCs, little is known about these factors important to plant health. With this in mind I isolated fungal endophytes from leaves of Populus trichocarpa and Populus fremontii, tree species with economic and environmental uses, to determine if endophyte communities are reserved between the closely related tree species and over seasons. Surface sterilized leaf fragments were plated onto malt extract agar and the resulting fungi were DNA sequenced and vouchered once significant biomass grew. I sequenced the ITS region of rDNA to determine fungal and tree species. Ultimately, I found that the host species had a slight effect on endophyte community composition during the summer. I also found that there was no significant seasonal difference in foliar endophyte communities of P. fremontii during the summer and fall. Taxa of interest included Penicillium, Mycosphaerella, Cladosporium, and Marssonina. Following endophyte isolation, I assayed the VOC profiles of the aforementioned taxa. The microbial VOC profiles were assessed using solid phase microextraction (SPME) and GCMS techniques. SPME fibers were inserted airtight tubes containing malt extract agar and two weeks of fungal growth for an hour. Fibers were then subjected to a GCMS run where absorbed VOCs were desorbed into the GCMS to be identified via the NIST molecular library. Penicillium and Cladosporium released styrene, a compound known for its antimicrobial effects. Marssonina and Mycosphaerella emitted phenylethyl alcohol, a compound with multiple industrial uses. Marssonina also released aristolochene and valencene, known precursors to mycotoxins. Through this work, I have shown that poplar foliar microbiomes are influenced by hosts and that foliar microbes can produce volatile compounds with economic and botanical significance.

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