Mainly high phenotypic stability of black spruce clones for growth and wood traits in contrasted environments within the current breeding zones and multitrait selection in Québec's seed and breeding zones

Selected trees from various progeny trials cannot be directly compared. As parents of clonal seed orchards and components of the next breeding cycle, it is crucial to verify their stability in different soil and climatic conditions and to rank them for multiple traits. A subset of the best trees selected for height at 10 or 15 years was cloned to establish 2 clone trials per population for 4 breeding populations, covering different bioclimatic domains of Québec. Between 80 and 119 clones per population were compared for height, diameter at breast height, indirect measure of wood density (Pilodyn 6J Forest device) and acoustic velocity (Fiber-gen Hitman ST300). Linear mixed models were used to estimate various genetic parameters, including genotypic values, using the Best Linear Unbiased Prediction (BLUP) method. With the genotypic values at 15 or 16 years for acoustic velocity and height, a selection index was calculated for ranking the clones. Clonal variances are significant for all growth and wood traits. Clonal heritabilities are low for growth traits with 1 exception (0.11-0.30) and range mainly from moderate to high for wood traits (0.29-0.70). Genotype × environment (G × E) interactions for growth traits are low for 2 populations (0.87-1) and mainly moderate for the 2 others (0.53-0.92). For wood traits, G × E interactions are low to almost nil and are mostly moderate for 1 population (0.69-1). In general, clones exhibit high stability (2 BLUP-based stability indexes) for growth and wood traits in contrasting soil and climatic conditions, except for the growth traits of 2 populations.