Study of early selection in tree breeding - 3. A case study using early information to enhance selection efficiency in late trait in lodgepole pine (Pinus contorta spp. Latifolia)

We present a selection procedure that combines early performance from retro spective study and late performance from field testing into an index design ed for enhancing the selection efficiency of the late performance. The prer equisite is that early performance from retrospective study and late perfor mance from field testing must correlate genetically. This selection index p rocedure is particularly applicable when practical considerations make seed ling selection of early traits preferable. An example is the study of bioma ss partitioning where young trees could offer a solution for large stale ev aluation and serve as a useful first approximation to what might be expecte d in older trees. To numerically illustrate this selection procedure, we pr esent a case study of retrospective early selection in 110 open-pollinated families from Alberta lodgepole pine (Pinus contorta spp. latifolia). Twent y-eight glasshouse traits in seedlings and the 9-year tree height of their siblings on four sites were conceived as the early and late traits, respect ively. Five greenhouse traits having highest genetic correlations with over all held performance were selected and indices of one and two traits from t hese five glasshouse traits with 9-year tree height averaged 3.0% and 6% mo re efficient, respectively, relative to selection based on 9-year tree heig ht alone. 24 seedling traits which had highest correlations with the field site height were selected for combination with 9-year tree height of one si te. Their efficiencies, relative to selection based on 9-year tree height a lone, for indices of one and two of glasshouse traits averaged 40% and 55% greater, respectively, than selection based on 9-year tree height alone. Th is demonstrates the potential of early retrospective genetic study to enhan ce later mature selection.