Determination of Optimum Selection Ages: A Simulation Approach

Prediction models of growth (height and stem volume), phenotypic variation, heritability, and age-to-age correlations provided an integrated framework for predicting optimum selection ages in a breeding program of fixed duration. The risks of early selection were assessed by computing a minimum significant gain ratio of juvenile selection; only gain ratios exceeding this minimum were permissible options for juvenile selections. Optimum selection ages were either very low (usually below one-sixth of the rotation age) or equal to the rotation age itself. Although intermediate selection ages promised more gain per unit time than selection at rotation age, the gain did not outweigh the associated risk. Slow growth (high rotation) made juvenile selection more attractive than it was in the fast growth scenarios. Minor changes in model parameters often had dramatic impacts on the age of optimum gain ratio. The simulation approach to estimation of optimum selection ages provides an useful tool for sensitivity analyses of a gain expression with many interrelated parameters.

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Author(s): Steen Magnussen

Publication: Tree Improvement and Genetics - Southern Forest Tree Improvement Conference - 1989

Section: Concurrent Session 1B