Influence of progeny and initial stand density on growth and quality traits of 21 year old half-sib Scots pine (Pinus sylvestris L.)

Forest tree breeding aims to identify genotypes whose offspring will grow well in operational plantations. However, relatively little is known about the competitive environment and how it affects the performance of genotypes. In this study we compared differences in growth (height, diameter, and volume) and external quality traits (diameter of thickest branch, stem straightness, branch angle, occurrence of spike knots and double stem) between (1) 10 half-sib Scots pine (Pinus sylvestris L.) families planted in plots with different genetic compositions and (2) 30 half-sib Scots pine families planted at three different densities. The results indicated that families performed differently depending on the genetic composition of the trees in their surroundings. Most of the traits showed low correlations between families in different genetic contexts and, occasionally, this had a large effect on rankings. Although these results are only from one trial, breeding programs may have to take this into consideration when designing field experiments. Furthermore, family performance also differed depending on planting density. This was especially true for quantitative traits: all such traits exhibited significant spacing × genetic entry interactions.

► We studied how competition affect performance of Scots pine families. ► Family performance in growth and quality was affected by the family of neighbors. ► Family performance in growth was affected by planting density. ► Family performance differed depending on the competitive environment.