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Wood quality and growth characterization across intra- and inter-specific aspen hybrid clones Hart, James Foster


Trembling aspen (Populus tremuloides Michx) is Canada’s most abundant poplar species; it is native, found nationwide, and is an ecologically and economically important hardwood species. As the demand for raw material continues to rapidly increase, there is an incentive to improve tree quality and growth rates through breeding, particularly in fast-growing species suitable for the Canadian landscape. Hybridization is considered one of the best options to accelerate tree productivity and improve wood quality. Two aspen species showing particular promise for hybridization with trembling aspen are European aspen (P. tremula) and Chinese aspen (P. davidiana) because their native climates are similar to that of western Canada. In 2003, poplar clones were planted in Athabasca, Alberta from the following species crosses: open pollinated (OP) P. tremuloides (NN), OP P. davidiana (CC), P. tremula × P. tremula (EE), P. tremula × P. tremuloides (EN), and P. tremuloides × P. davidiana (CN). In, November 2010, growth measurements and core samples were taken from the clones. Productivity was quantified through analysis of stem volume. Wood quality attributes were quantified via an assessment of fibre length, fibre width, coarseness, wood density, microfibril angle, total cell wall carbohydrate and lignin content, and lignin composition. Comparisons of the mean values for each attribute were made between crosses using generalized linear model least squares means tests. The NN cross had lower volume growth than the CC and EE crosses. The EN and CN crosses had greater volume than the NN cross. The NN cross had shorter fibre length, but greater syringyl-guaiacyl ratio (S:G) relative to the CC cross. It also had lower density and S:G compared to the EE cross. The EN cross had longer, wider fibres and a greater carbohydrate concentration compared to the NN cross. The CN cross had greater fibre length and lignin concentration, but lower S:G compared to the NN cross. The results indicated that the inter-specific crosses were more desirable wood sources than the pure P. tremuloides cross. Specifically, the P. tremula x P. tremuloides cross showed the best potential to improve future generations of aspen on the Canadian landscape.

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