Genetic parameters of growth characters in Salix viminalis grown in Sweden

Forty families of Salixviminalis L. from an eight by eight factorial crossing were planted in contrasting environments to estimate genetic additive, dominance, and epistatic variances and to estimate the impact of genotype–environment interaction. From each family, 14 seed plants were vegetatively propagated. The material was planted in two contrasting soils, heavy clay soil and sandy soil, and in two contrasting nutrient availabilities, high and low. The nutrient experiment was harvested annually for 3 years. The clay–sand experiment was harvested in the 1st, 4th, and 6th year. Height, diameter, weight, and number of shoots were measured. Additive genetic variance was found, but there were large standard deviations in many of the estimates, especially in the nutrient experiment. Dominance and epistatic variances of greater significance were found for weight characters in the clay–sand experiment. Narrow-sense heritability estimates varied, with the highest estimate being 0.34. Genotype–environment interaction seems to be of greatest importance in the establishment years in the soil contrast but of increasing importance in the nutrient contrast. Breeding strategies in connection with these findings are discussed.