Characterization of Secondary Metabolites from Douglas-Fir Endophytes to Guide the Development of Applications Reducing Swiss Needle Cast

Abstract

Douglas-fir (Pseudotsuga menziesii) is one of the most economically important softwood trees grown worldwide, although the past several decades have seen a decline in productivity due to infection of the endemic fungus Nothophaeocryptopus gaeumannii which causes the disease Swiss needle cast. Conifer endophytes have previously been shown to produce toxins in planta capable of mitigating herbivory and other pathogens. A bioassay was developed to assess the antifungal properties of culture filtrate extracts from 59 Douglas-fir endophytes against N. gaeumannii.Twenty-six strains that significantly inhibited the growth of N. gaeumannii were identified. In addition, 17 metabolites from Douglas-fir endophytes, including Xylaria hypoxylon, Rhabdocline parkeri, and Coleophoma sp. were isolated, including a new class of tetronates from R. parkeri.The aim of this study was to identify biologically active Douglas-fir endophyte extracts to direct future investigations profiling bioactive natural products. Endophytes that inhibit N. gaeumannii will be prioritized for future studies to determine their potential in forest management applications. I would like to first thank my supervisors Dr. David McMullin and Dr. Joey Tanney for providing me the opportunity to conduct this research and introducing me to the field of natural product chemistry. Your combined enthusiasm, kindness and knowledge has been invaluable and has taught me much about the importance of collaboration in research. While it's true that nothing's easy, I do feel that much of the challenge of the past two years has been alleviated by your expertise. I would like to specifically thank Joey Tanney for his work in collecting and identifying the fungal species included in this thesis, and David McMullin for knowing just the right amount to push. Thank you to Dr. Tyler Avis for being generous with his time to give advice regarding bioassays, statistical analysis, or anything else that I had a question about. Thank you to Dr. Mark Sumarah and Dr. Justin Renauld at Agriculture and Agri-food Canada for the acquisition of HRMS data. Thank you to Dr. Véronic Bezaire for inviting me to get involved in multiple opportunities to teach that I would not have considered otherwise. Much of what I have learned about effective scientific communication and the joy of being an educator has come from you. And thank you to Prof. David Miller for taking the time to provide advice and share what I'm sure is only a fraction of his mastery of toxicology and fungal secondary metabolites. Thank you for continually demonstrating the importance of considering the impact of a scientist's work beyond the laboratory. Thank you to Irbaz Rehman, Emily Marion, and Marin Netterfield for their extremely valuable technical assistance that contributed to this work. I appreciate all of you understanding when my brain simply had no thoughts.