Genetic parameters and performance stability of white spruce somatic seedlings in clonal tests.

Abstract: The commercial use of white spruce varieties produced by somatic embryogenesis (SE) permits increased forest productivity compared to other reproductive technologies. However, the use of SE in clonal forestry requires an accurate assessment of genetic parameters and the performance stability of clones in plantations. For these reasons, two clonal tests were established of 52 white spruce somatic clones. In each clonal tests, we measured survival, bud dormancy, stem form, growth and branching characteristics of clones 4years after outplanting. There was a large variability among clones for characteristics related to growth and branching. At this juvenile stage, the clonal heritability estimates for all characteristics remained low. Of all the characteristics studied, height had the highest heritability. The selection of the top 20 clones (38% of the clones) provided a genotypic gain in height of about 4% for the two planting sites, which is reasonable for such a low selection intensity. High genotypic correlations were observed between growth and branching characteristics. Although a significant site effect was observed for most characteristics, the genotype×site (G×E) interaction was low and consequently the correlation between the two sites for the same characteristic was high. The performance stability of the somatic clones at both sites indicates that opportunities exist for selection of clones that adapt and perform well over different ecological regions, permitting a tangible increase in forest productivity. [Copyright &y& Elsevier]