This study represents the second in a series investigating the additive genetic variance operating within an unselected population of Sitka Spruce trees of known single origin. The first study presented by SAMUEL and JOHNSTONE (1979) looked at height between 1 and 6 years from planting. This study looks at the additive genetic control of growth traits at just one site up to 23 years from planting. Basic genetic statistics for each individual trait are presented along with the genetic relationship between each trait and the optimum ages of selection relative to mature ages of 23 years and 40 years. Analysis was carried out at both the individual tree and family-mean level. The optimum individual tree and family mean selection ages in terms of generation efficiency were 9 year height and 23 year diameter respectively. When selection was based on genetic gain per year, the optimum ages were again 9 year height at the individual tree level, but fell to 5-year height at the family-mean level. There was very little difference in optimum selection ages depending on the age of the mature trait. Efficiencies could be improved and selection ages reduced if the delay necessary to bring juvenile selections to flower could be reduced to just 3 years or 5 years.
|Number of pages||11|
|Publication status||Published - 2002|
- Picea sitchensis genetic correlations phenotypic correlations heritability indirect selection juvenile-mature correlations information britain