Inheritance of growth and solid wood quality traits in a large Norway spruce population tested at two locations in southern Sweden

Abstract

Unfavorable genetic correlations between growth and wood quality traits are one of the biggest challenges in advanced conifer breeding programs. To examine and deal with such correlation, increment cores were sampled at breast height from 5,618 trees in 524 open-pollinated families in two 21-year-old Norway spruce progeny trials in southern Sweden, and age trends of genetic variation, genetic correlation, and efficiency of selection were investigated. Wood quality traits were measured on 12-mm increment cores using SilviScan. Heritability was moderate (~0.4-0.5) for wood density and modulus of elasticity (MOE) but low (~0.2) for microfibril angle (MFA). Different age trends were observed for wood density, MFA, and MOE, and the lower heritability of MFA relative to wood density and MOE in Norway spruce contrasted with general trends of the three wood quality traits in pine. Genetic correlations among growth, wood density, MFA, and MOE increased to a considerably high value from pith to bark with unfavorable genetic correlations (−0.6 between growth and wood density, −0.74 between growth and MOE). Age-age genetic correlations reached 0.9 after ring 4 for diameter at breast height (DBH), wood density, MFA, and MOE traits. Early selections at ring 10 for diameter and at ring 6 or 7 for wood quality traits had similar effectiveness as selection conducted at reference ring 15. Selection based on diameter alone produced 19.0 % genetic gain in diameter but resulted in 4.8 % decrease in wood density, 9.4 % decrease in MOE, and 8.0 % increase in MFA. Index selection with a restriction of no change in wood density, MOE, and MFA, respectively, produced relatively lower genetic gains in diameter (16.4, 12.2, and 14.1 %, respectively), indicating such index selection could be implemented to maintain current wood density. Index selection using economic weights is, however, recommended for maximum economic efficiency.

Estimating solid wood properties using Pilodyn and acoustic velocity on standing trees of Norway spruce

“…In this study, the CV A of acoustic MOE was similar to benchmark MOE calculated on data from all rings but lower than the benchmark as estimated excluding the outermost rings (>ring 15) (Chen et al 2014). The heritabilities of the acoustic MOE (0.28-0.31) were slightly lower than those of the benchmark MOE calculated on all rings (0.33), which was however lower than the benchmark MOE for rings 1-15 (0.38).…”

“…A randomized incomplete block design using single-tree plot was used in both trials. Detailed descriptions about field design, soil type, and climate condition were given in the previously published paper (Chen et al 2014). The current study is based on a subset of 524 families.…”

“…The details of sampling for increment cores, measurements of density, MFA, and MOE with SilviScan and calculations of area-weighted averages representing cross sections were shown in the paper (Chen et al 2014). In the current work, area-weighted mean wood properties of density, MOE, and MFA for each increment cores were calculated based on all rings of the increment cores, 24 % of the cores having 15 or less rings, 65 % having 16-17 rings, and about 11 % having 18 to 19 rings.…”

“…In the current work, area-weighted mean wood properties of density, MOE, and MFA for each increment cores were calculated based on all rings of the increment cores, 24 % of the cores having 15 or less rings, 65 % having 16-17 rings, and about 11 % having 18 to 19 rings. In Chen et al (2014), however, all calculations were based on area-weighted averages for 15 rings for consistency and as the outermost rings are sometimes influenced by the sampling. This resulted in higher heritabilities of 0.52, 0.23, and 0.38 for wood density, MFA, and MOE, respectively.…”

“…These two heritabilities were also similar to the heritability of the benchmark MOE 21 (0.33). This may also be compared to the heritability of 0.38 obtained for benchmark MOE based on annual rings 1-15 (Chen et al 2014), indicating that calculation with data of the same age for all trees and exclusion of rings where data may have been influenced by sampling provides higher heritability. A similar pattern was observed for MFA.…”