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

To better understand the genetic control of wood chemical and fibre propert ies in hybrid aspen, genetic relationship of these with growth and phenolog ical traits were examined. In all, 18 hybrid aspen clones were sampled in t he 13- and 14-year-old clone trials in Sweden. Strong clone within family e ffects were present for growth and wood properties. The repeatability estim ates across two sites were 0.85. 0.65. 0.56, 0.54, and 0.65 for alkali solu ble lignin content, arithmetic average fibre length, coarseness, diameter, and height, respectively. Genetic correlations generally exceeded the corre sponding phenotypic correlations. The phenotypic and genetic correlations w ere negative between fibre count and height growth (-0.64 and -0.65. respec tively) and between fibre count and length of growth period. The result sug gests that the length of the growth period could be a good predictor of clo ne 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 ge netic correlations indicated that wood characters were more stable than gro wth traits.