Phenotyping a Pinus radiata breeding population for resin canal traits

Resin defects can substantially decrease timber value in Pinus radiata , a commercial forest plantation species known for its good machinability. Tree breeding is a common approach to improve economic viability and product quality in commercial forestry. This study evaluated resin canal features in a P. radiata breeding population at two sites. Phenotypic resin canal features close to the pith differed significantly between the sites. The study estimated heritabilities for resin canal size, area, and density in 2-year-old trees as h 2 = 0.25, 0.42 and 0.23, respectively. The corresponding coefficients of genetic variations were 7.7%, 22.6% and 15.2%. Furthermore, resin canal features were assessed along radial cores of 6-year-old trees. Resin canal size increased with cambial age, while resin canal density and area showed minima 4 cm from the pith. Radial changes were accompanied with increased variation between families. While heritability and genetic variation would allow for selection at age 2-year-old, increased variation further from the pith could allow more accurate selections when trees are older. Genetic correlations between resin canal traits indicate that genotypes with larger resin canals tended to have fewer canals, larger trees having bigger but fewer resin canals and stiffer trees having less resin canal area.