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Breaking the wall of silence of trees Mining metabolomics to describe hybridization and predict performance in the Populus – Sphaerulina musiva pathosystem Open Access


Other title
machine learning
Sphaerulina musiva
benzoic acid derivatives
Type of item
Degree grantor
University of Alberta
Author or creator
Najar, Ahmed
Supervisor and department
Nadir Erbilgin (Renewable Resources)
Barbara Thomas (Renewable Resources)
Examining committee member and department
Andreas Hamann (Renewable Resources)
Stephen Strelkov (AFNS)
Tariq Siddique (Renewable Resources)
Peter Constable (University of Victoria)
Department of Renewable Resources
Forest Biology and Management
Date accepted
Graduation date
2017-11:Fall 2017
Doctor of Philosophy
Degree level
Stem canker diseases in poplars caused by the fungal pathogen Sphaerulina musiva Peck. remain some of the least understood forest diseases despite causing considerable damage, particularly in hybrid poplar plantations. S. musiva is endemic to eastern Canada in provinces including the Maritimes, Quebec, and Ontario. Although these provinces contain poplar species such as Populus deltoides (Bartr.) Marsh and P. balsamifera L., they are purported to be resistant to the Septoria canker in their eastern range. The Northwestern range (Alberta and British Columbia) mainly home to P. balsamifera and P. trichocarpa Torr. and Gray., the pathogen is found sporadically in shelterbelts, nurseries, and plantations. Anthropogenic crosses among native species of poplars in North America or with exotic species have been undertaken to produce clones with ‘hybrid vigour’ which combine high growth rates with ease of propagation and disease resistance. While vigour of hybrid trees can be modeled and predicted, it is still challenging to predict disease performance in anthropogenic crosses. In the present work metabolic phenotyping was successfully used as a way of predicting performance in various cross types in response to S. musiva. In its native range, P. balsamifera in Alberta has shown high susceptibility to stem canker, unlike its eastern counterpart. Selected genotypes with variable introgression levels with P. trichocarpa and covering the spectrum from P. trichocarpa to P. balsamifera were inoculated with a fungal spray mixture of S. musiva and their phenomics measured both visually (infection estimates) and phytochemically. Susceptibility in P. balsamifera was linked to two parameters: (1) the level of admixture with P. trichocarpa; and (2) their evolutionary history. Metabolic phenotyping identified metabolites involved in the genotypic responses to S. musiva and other metabolites describe hybridization between different species. Using genetic characterization along with phenomic data provides predictive tools to inform tree breeding programs, shape management decisions, and sheds light on the poorly understood Populus – S. musiva pathosystem.
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