Genetic variation of height growth and expected gain from selection in a Minnesota population of black spruce (Picea mariana): Field evaluations and their correlation with greenhouse and nursery data

Black spruce (Picea mariana (Mill.) B.S.P.) is a quality species for pulp and solid wood products, but its slow growth rate limits its use in plantation forestry in Minnesota. A breeding project was initiated in 1974 with a goal of improving the growth rate of black spruce. The objectives of this dissertation were (i) to estimate the additive genetic and non-additive genetic variance components of height growth and the expected gain from alternative selection methods, (ii) evaluate the effect that these selection methods have on inbreeding levels in the rogued seedling seed orchards, (iii) estimate age-age genetic and non-genetic correlations and evaluate the potential of early selection, (iv) investigate the effects of divergent selection on genetic variance and selection response, (v) evaluate the effect of inter-provenance hybridization, and (vi) estimate the dominance genetic variance of height growth. Data from four wind-pollinated family tests were analyzed to meet the first three objectives. Three controlled pollination experiments were initiated to meet the final three objectives. Additive genetic variance was relatively small and accounted for 8, 10 and 11 percent of the total phenotypic variance at ages 7, 10 and 12 years from seed, respectively. Family by location interaction variance was significant and appeared to be increasing with time. Under a random mating model and an assumption of a 10 percent loss in mean height per.10 increase in average inbreeding level, the theoretically most efficient selection method (index, family plus individual) was also most efficient. Age-age genetic correlations between greenhouse or nursery and field measured heights were positive but in all cases less than.20. Phenotypic and error correlations were also positive and generally twice as large. Early selection based on height does not appear useful until four or more years of field-growth have occurred. Divergent selection for age 10 height did not result in a significant effect on greenhouse height, supporting the above conclusion on early selection. Inter-provenance (Newfoundland, New England, Ontario, Alberta and Minnesota sources) crosses were significantly taller in the greenhouse than intra-provenance crosses. Dominance genetic variance of greenhouse height was not significant when estimated from four disconnected factorial matings.