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Characterizing the changes in host tree chemistry after cutting and revisiting the nutritional role of fungi in the novel mountain pine beetle host jack pine
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- Author / Creator
- Guevara Rozo, Sydne G
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Studies with conifer-infesting bark beetles commonly use tree bolts to evaluate the effects of host tree quality on various aspects of insect biology. Yet, whether host quality changes between live trees and bolts cut from these trees has not been assessed. Particularly, changes in concentrations of defense chemicals and nutrients have not been compared between live trees and their cut bolts. To determine whether monoterpene and nutrient concentrations differ after cutting, jack pine trees in Lac La Biche (Alberta) were selected and sampled for phloem tissue. Then, these trees were harvested into two bolts per tree and stored at 4°C. Phloem from one bolt was sampled after three months of storage and from the second bolt six months after cutting. I found that major monoterpenes of jack pine were higher in phloem from bolts than live trees. Storage time did not affect the results. Furthermore, some nutrients including nitrogen were also higher in bolts and varied between storage times. I conclude that researchers should be aware of the observed changes in the host quality which may have positive or negative effects on the development of bark beetles.
In addition, to determine how they change host quality in bolts, I evaluated the nutritional benefits that were provided by fungi associated with the mountain pine beetle. Mountain pine beetle is commonly associated with three symbiotic fungi: Grosmannia clavigera, Ophiostoma montium, and Leptographium longiclavatum. These fungi are an important source of nitrogen and ergosterol for beetles as plant tissues are low in nitrogen, and ergosterol cannot be synthesized by insects. In lodgepole pine, it has been reported that both nitrogen and ergosterol concentrations increase in the presence of these fungi; however, the relative contribution of each species is unknown. I investigated the nutritional benefits of the three fungi in terms of their ability to concentrate nitrogen and to produce ergosterol in the jack pine phloem. Eighty jack pine trees occurring in two forest stands in Alberta were inoculated with live culture plugs of each of the three fungi or non-colonized media (mock inoculation, control) (n=20 trees per trt). Six weeks later, phloem samples were collected from within and outside of the lesions caused by fungal infections. A single tissue of mock inoculated trees was also collected. Nitrogen and ergosterol concentrations were determined, and results indicated that total nitrogen in lesions varied with fungal species, being higher in control trees and O. montium lesions. Furthermore, ergosterol incidence was significantly higher in lesions compared to the samples from outside lesions. I found a higher ergosterol concentration in lesion sampled from O. montium than from G. clavigera and L. longiclavatum. My results indicate that O. montium may provide an advantage in terms of ergosterol availability during the development of the mountain pine beetle larvae. -
- Subjects / Keywords
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- Graduation date
- Fall 2018
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- Type of Item
- Thesis
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- Degree
- Master of Science
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- License
- Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.