Genetic parameters for spiral grain in Scots pine and Norway spruce

Genetic parameters were estimated for grain angle, growth and exterior quality traits in two 18-year-old Scots pine ( Pinus sylvestris L.) progeny trials and for grain angle and growth traits in two 12-year-old clonal trials of Norway spruce ( Picea abies L. Karst.). Mean grain angles ranged 1.4 to 2.0 degrees and 2.1 to 2.6 degrees in the Scots pine and Norway spruce trials, respectively. Heritabilities for grain angle were high in Scots pine ( h 2 >0.40) and moderate in Norway spruce ( H 2 >0.30). The genetic standard deviations were around or slightly below one degree. In general, grain angle was genetically and phenotypically uncorrelated with the growth and exterior quality traits. All traits showed low amount of genotype by environment interaction and there was no tendency of grain angle being a more stable traits than the other traits studied. A newly developed measurement device for grain angle where the grain angle is revealed by a wedge that is pushed through the bark into the wood and follows the inclination of the tracheids was tested and found suitable for measurements in genetic tests.