Age trends in genotypic variation of wood density and its intra-ring components in young poplar hybrid crosses

Abstract

-Age related dynamics of genotypic, phenotypic, and environmental variation, clonal repeatability, and genotypic correlations for wood density and its intra-ring components were analyzed in four poplar hybrid crosses, Populus deltoidesˆP. nigra, P. trichocarpaˆP. deltoides, P. maximowicziiˆP. balsamifera, and P. balsamiferaˆP. nigra, as well as P. deltoides. Using X-ray densitometry, measurements were taken on increment cores sampled in four clonal trials at 10 and 12 years of age from ramets of 19 clones. Wood density of all hybrid crosses was highest at the pith and decreased with increasing cambial age. The significance of the hybrid cross effect increased with age for mean wood density, dry fiber weight, and ring width. The coefficient of genotypic variation of cumulated mean wood density was rather stable over the 10-year period at all three sites, and ranged from 4.8-6.8%. Clonal repeatability increased with age from 0.46 to 0.79, mainly because of decreasing random variation. Corresponding genotypic parameters for individual rings varied greatly with age and across sites. Significance of the site effect on wood density tended to decrease with age. Significant negative genotypic correlations between ring width and wood density were found at only two of the four sites and they weakened with age. Age-age genotypic correlations between wood densities at ages 10 and younger were strong and significant from age 6 and over. This trend suggests that selection before this age would be unreliable. poplar hybrids / clones / wood density / radial growth / age trend / genotypic variation / repeatability / genotypic correlation Résumé -Variabilité génotypique inter-annuelle de la densité du bois et de ses composantes intra-cerne chez de jeunes peupliers hybrides. La dynamique inter-annuelle de la variabilité génotypique, phénotypique et environnementale, de la répétabilité clonale et des corrélations génotypiques entre paramètres de densité du bois ont été analysées pour quatre hybrides de peuplier : Populus deltoidesˆP. nigra, P. trichocarpaˆP. deltoides, P. maximowicziiˆP. balsamifera, and P. balsamiferaˆP. nigra, ainsi que pour P. deltoides. Les mesures ont été effectuées par microdensitométrie à rayon X sur des carottes échantillonnées à partir des ramets de 19 clones issus de quatre tests clonaux (âge : 10 et 12 ans). Les résultats montrent que la densité du bois de tous les hybrides est la plus élevée près de la moëlle puis qu'elle diminue avec l'âge cambial. L'effet statistique du type d'hybrides augmente avec l'âge pour la densité moyenne, le poids sec des fibres et la largeur de cernes. Les coefficients de variation génotypique pour la densité moyenne du bois sont stables au cours des 10 ans sur 3 sites et s'élèvent à 4.8-6.8 %. La répétabilité clonale augmente avec l'âge de 0.46 à 0.79. Les paramètres génotypiques pour les caractéristiques individuelles des cernes varient fortement avec l'âge et les sites. Le degré de signification de l'effet site tend à décroître avec l'âge pour la densité du bois. ...

Genotypic variation and heritability of growth and adaptive traits, and adaptation of young poplar hybrids at northern margins of natural distribution of Populus nigra in Europe

“…Because of mismatching between test locations and deployment zones, G  E interaction, if improperly accounted for, can result in bias of estimates and thus in decrease of genetic gain. The hybrid  site interaction for dry biomass production was found to be significant in our previous study [44,42] while it was not significant in other study in which only two sites and fewer hybrids were investigated [43]. The interaction may be related to differences between hybrids in adaptability to unfavourable or stressful site conditions.…”

“…Tree conditions and survival rates in the Dubrava site were lower, possibly due to damage to tree stems by rodents. Strongly significant site effects were obtained for growth traits, stem volume and dry fibre biomass in previous studies of hybrid poplars tested in southern Quebec in Canada on four sites [44,42] and on eight sites [50]. The large site effect was found in yield, on the most productive site being as high as 22.4 m 3 ha À1 y À1 and on the poorest site as low as 1.1 m 3 ha À1 year À1 [50].…”

Genetic correlations between wood quality traits of Pinus pinaster Ait

“…Nevertheless, variations in wood density can be difficult to understand, since this complex trait is not a single property but a complex of several intra-ring components, including minimum and maximum wood densities, early and late wood densities, proportion of latewood etc (Pliura et al, 2006). Another important wood property is the spiral grain, a term applied to the helical orientation of the tracheids in a tree stem.…”

Prediction of wood density breeding values of Pinus taeda elite parents from unbalanced data: A method for adjustment of site and age effects using common checklots

“…Age-age correlations of wood density need to be explored for fast growing elite families to study possible undue effect on growth traits. In the literature, strong age-age correlations were reported for wood density in hybrid poplar clones (Pliura et al, 2006). Wu et al (2007) reported stable wood density values from ages 11-15 to rotation-age in Pinus radiata, which is encouraging.…”