Heritability and Correlations for Biomass Production and Allocation in White Spruce Seedlings

Tree growth is a multidimensional trait and families vary for components of growth such as height, diameter, foliage and roots. Therefore, variation in tree growth is better studied by analysing biomass production and allocation than simple traits. In addition, biomass is better linked to products such as pulp and wood energy than simple traits. We analysed biomass of 3-year old open-pollinated greenhouse seedlings of white spruce to determine (1) heritability for biomass production and allocation to shoot and root components, (2) correlations between biomass traits, and biomass traits with primary traits, and (3) correlation between biomass production in the greenhouse and height growth for the same families in the field. The study had a randomised complete block design with single-tree plots, 30 blocks and 58 open-pollinated families. Individual-tree heritability (h_i² ) and family mean heritability (h_f² ) ranged from 0.200 to 0.333 and 0.374 to 0.516 for green weight, respectively. Likewise, h_i² and h_i² ranged from 0.186 to 0.359 and 0.352 to 0.536 for dry weight, respectively. Genetic correlation (r_a) between green and dry weight ranged from 0.943 to 1.015, while r_a between shoot and root dry weight ranged from 0.947 to 0.955. In contrast, r_a between biomass traits and field height ranged from -0.403 to -0.124. Thus, we conclude (1) variation in biomass production and allocation exhibited low genetic basis, (2) testing and selection for green or dry weight should lead to similar genotypes, (3) biomass allocation may not be easily altered by selection and breeding, and (4) indirect early selection based on seedling biomass