Genetic control of wood physicochemical properties, growth, and phenology in hybrid aspen clones

To better understand the genetic control of wood chemical and fibre properties in hybrid aspen, genetic relationship of these with growth and phenological traits were examined. In all, 18 hybrid aspen clones were sampled in the 13- and 14-year-old clone trials in Sweden. Strong clone within family effects were present for growth and wood properties. The repeatability estimates across two sites were 0.85, 0.65, 0.56, 0.54, and 0.65 for alkali soluble lignin content, arithmetic average fibre length, coarseness, diameter, and height, respectively. Genetic correlations generally exceeded the corresponding phenotypic correlations. The phenotypic and genetic correlations were negative between fibre count and height growth (-0.64 and -0.65, respectively) and between fibre count and length of growth period. The result suggests that the length of the growth period could be a good predictor of clone differences in fibre count. The estimated correlations were unfavourable, in the sense that clonal selection directed at increasing the fibre count is expected to produce an indirect genetic decline in growth. Intersite genetic correlations indicated that wood characters were more stable than growth traits.