Genetic Parameters for Bud Flushing and Growth Characteristics of White Spruce Seedlings

We estimated heritabilities and correlations for bud flushing and growth traits of white spruce seedlings, and the correlations of seedling traits with 10- and 11- year height of the same families in the field. The seedling greenhouse experiment had a randomized complete block design with 30 replications, 58 open-pollinated families and single-tree plots. Individual tree heritability (h_i²) was 0.78 and 0.54 for 18 (H18) and 36 (H36)-week total height, respectively. The corresponding heritabilities for family means (h_f²) were 0.91 and 0.82. For root collar diameter, hi 2 were respectively, 0.61 and 0.22 at 24 and 54 weeks from germination. The corresponding h_f² were 0.87 and 0.55. Heritability for bud flushing ranged from 0.13 to 0.46 (h_i²) and 0.44 to 0.83 (hf 2). The genetic correlation (r_a) between H18 and H36 was 0.70 and that of D24 and D54 was 0.89, indicating a substantial change in family ranking in one growing season. The type B genetic correlation for H18 with field heights ranged from 0.22 to 0.30. Type B genetic correlations of field height with all other seedling traits were very low and largely negative. It can be concluded that: (1) age-age correlation of seedling height can be expected to decline drastically even in a stable environment of the greenhouse, (2) heritability for growth potential is meaningful when estimated on cumulative growth not on individual annual growth increments that are susceptible to short-term environmental variation, (3) dates of bud flushing did not influence variation in height and root collar diameter, and (4) field growth potential is better predicted by greenhouse growth potential than other morphological and shoot phenological traits.