Natural Product Discovery and Mycotoxin Analysis of Agricultural Endophytes and Pathogens
Abstract
This thesis focuses on the application of fungal natural product chemistry for the use of agriculture fungal pathogenesis research. The research in this work uses many analytical chemistry techniques and instruments such as HPLC, LC-MS/MS and NMR. In Chapter 2, a diagnostic fragmentation module was developed for the identification of compound classes in crude fungal extracts. This module identified the classes cytochalasins and chaetoglobosins from extracts of Penicillium, Chaetomium, and Xylaria. From these extracts a new chaetoglobosin was discovered and the module was implemented into the open-source software package MZmine 2.0. Chapter 3 discusses analytical chemistry techniques with the quantification of mycotoxin exposure in an at-risk population of Rwandan women through biofluid screening. The quantitated mycotoxins include deoxynivalenol, aflatoxin, zearalenone, fumonisin, and ochratoxin in addition to their derivatives. In total, 11 mycotoxins were quantified using isotopically labelled internal standards, with this chapter also overviewing their simplified synthesis. This study revealed the importance of mycotoxin screening and control in these at-risk populations. Chapters 4 – 6 of this thesis is focused on Ilyonectria mors-panacis and its pathogenicity as root rot on American ginseng. In Canada it is expected at time of harvest to lose about 20-30% of total crop yield to root rot with extreme cases experiencing severe loss of 80-100%. Ilyonectria root rot is also a major factor in the longer-term issue of replant disease, preventing subsequent plantings of ginseng in the same field for decades after initial planting. The work included in these chapters focuses on discovering new natural products from Ilyonectria mors-panacis and identifying virulence factors. Overall this pathogen produced a large number of resorcylic acid lactones, of which nine were isolated and identified, including a new natural product, Radicicol E. Additionally, an iron-chelating siderophore – N,N’,N”-Triacetylfusarinine C – was identified as a virulence factor and was pursued as a potential treatment method for root rot using enzymatic degradation. This treatment showed promising results for targeted treatment of ginseng root rot, however, application methods would need to be improved for practical use. Overall, this thesis explores a variety of disciplines which are required of a natural product chemist and demonstrates applications of natural product discovery.