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Metabolite variation in ecologically diverse black cottonwood, Populus trichocarpa Torr. & A. Gray Fayed, Manal A.


Black cottonwood (Populus trichocarpa Torr. & A. Gray) is mass productive tree species native to the Pacific Northwest of North America. Gas chromatography - mass spectrometry was used to study the metabolic profiling of leaves from multiple genotypes to investigate the presence of clinal trends in metabolite levels and to determine if relationships with geo-climatic variables and date of bud set exist. In the late summer (September 3rd) of 2008, young leaves were collected from the species’ range and represented by 106 clones grown in a common garden established in Vancouver, British Columbia, Canada. The results validity was verified through the use of two independent canonical correlation analyses (CCA) that were performed on the intensity of the detected 104 compounds, including 40 known metabolites. Principle Component Analysis (PCA) was performed for original variables reduction and to determine the principle components accounting for most of the variation (the first ten PCAs accounted for 63% of the variation). The first analysis utilized the metabolites associated with the first ten principal components to determine the relationship between the original metabolites and geography, climate and date of bud set, while the second was based on the first ten principal components themselves. Both analyses yielded strong to moderate trends but the correlations (ranging from 0.45 to 0.97) were not statistically significant most likely due to the small sample size used. Based on the analyses conducted, it appears that P. trichocarpa ecotypes are preconditioned to suite their location-origin and the observed differences in metabolites reflected the genotypic variability among the studied trees.

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