Genetic parameters of morphological and physiological characteristics of containerized white spruce (Picea glauca [Moench.] Voss) seedlings

The root systems of containerized seedlings must be sufficiently developed and have adequate root plug cohesion to permit handling and the planting of the seedlings with minimal root damage. Genetic variability in morphological and physiological seedling characteristics of 75 open-pollinated white spruce families was estimated to determine whether genetic selection for improved seedling root systems is possible. Seedlings were grown for 2 years under standard cultural practices in a forest nursery. Gas exchange measurements and seedling morphological characteristics (height, diameter, shoot and root dry mass, root to shoot ratio) were measured at the end of the two growing seasons whereas seedling mineral (N, P, and K) status was assessed at the end of the first growing season. Genetic parameters (heritabilities—h ²—and genetic correlations) were estimated for every seedling characteristic and a strong genetic control associated with a large genetic variation was observed at both family (0.20 ≤ h_f² h_f^2  ≤ 0.88) and individual (0.21 ≤ h_i² h_i^2  ≤ 0.97) levels. A single, late-season measurement of physiological characteristics did not reveal physiological basis for family variability in seedling root growth. Nevertheless, the family variation was large enough to permit genetic improvement of 2-year-old seedling juvenile morphological characteristics. Strong, positive genetic correlations enable us to foresee using root collar diameter as an effective method for indirectly selecting white spruce families with heavier root systems.