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Doctoral thesis, 2020

Quantitative genetics of wood quality traits in Scots pine

Fundova, Irena


Wood quality of commercial tree species is important for many wood processing
industries and thus should be considered for inclusion in forest tree improvement
programs. This thesis evaluated the suitability of various proxy methods for rapid and
non-destructive assessment of wood quality traits on standing trees of Scots pine and the
potential for genetic improvement of different wood quality traits through recurrent
selective breeding.

Penetrometer Pilodyn and micro-drill Resistograph were tested for non-destructive
assessment of wood density (DENPIL and DENRES, respectively), using SilviScan density
(DENSILV) as a benchmark. A strong additive genetic correlation was observed between
DENSILV and DENRES (rA = 0.96), whilst the correlation with DENPIL was substantially
lower (rA = 0.74). Furthermore, SilviScan stiffness (MOESILV) was used as a benchmark
for evaluation of several approaches of calculating the dynamic modulus of elasticity
(MOE) from standing-tree acoustic velocity (VELTREE). The combination of VELTREE
and adjusted DENRES provided the most accurate estimate of MOETREE (rA = 0.91).
Additionally, non-destructive acoustic sensing tools were tested at different stages of
wood processing (on standing trees, felled logs and sawn boards) using destructively
measured sawn-board stiffness (static modulus of elasticity, MOES) and strength
(modulus of rupture, MOR) as benchmarks. They proved to be capable of accurately
predicting MOES (rA ≈ 0.8) while VELTREE, adjusted DENRES and MOETREE well
reflected MOR (rA ≈ 0.9). Genetic variation of shape stability of sawn boards (bow, crook
and twist) was also investigated. Under-bark grain angle (GRA) was found to be a good
predictor of sawn-board twisting and crooking (rA = 0.84 and 0.62, respectively). The
chemical composition of juvenile wood (proportion of cellulose, hemicelluloses, lignin
and extractives) was predicted from Fourier transform infrared (FTIR) spectra using
partial least squares regression (PLSR) modeling. Individual-tree narrow-sense
heritabilities (ℎi2) for all of the studied wood quality traits varied from low to moderate.

Genetic improvement of sawn-board DEN, MOES and MOR as the target traits could
be achieved through selective breeding for MOETREE, DENRES, stem straightness (STR)
or GRA. Selection focusing on GRA would also result in lower bow, crook and twist.
Despite the negative genetic correlations between growth and wood quality traits, a
possibility of their simultaneous improvement was identified. An index combining stem
diameter (DBH) and MOETREE provided the best compromise.


Density; stiffness; strength; shape stability; chemical composition; non-destructive testing; genetic correlation; heritability; breeding; genetic improvement

Published in

Acta Universitatis Agriculturae Sueciae
2020, number: 2020:9
ISBN: 978-91-7760-536-2, eISBN: 978-91-7760-537-9
Publisher: Department of forest genetics and plant physiology, Swedish university of agricultural sciences