Age trends of microfibril angle inheritance and their genetic and environmental correlations with growth, density and chemical properties in Eucalyptus urophylla S.T. Blake wood

Context The genetic and environmental control of microfibril angle (MFA) and its genetic correlations with other wood and growth traits are still not well established in Eucalyptus sp. & Aims To determine the narrow-sense heritability estimates (h2) of MFA, wood density (D), Klason lignin (KL) content, syringyl to guaiacyl (S/G) ratio and growth traits, their variation from pith to cambium and their genetic correlations. & Methods Heritability and correlations were assessed in 340 control-pollinated progenies of 14-year-Eucalyptus urophylla S.T. Blake using near infrared spectroscopic models. & Results Moderate to high heritability were found for MFA (h200.43), D (h200.61), S/G (h200.71) and LK (h200.76). The genetic control of D andMFA and the genetic and residual correlation between chemical and growth traits varied with age. The genetic correlation C×D was always strongly negative (r<?0.80) while the correlation D×MFA remained constant and positive in the juvenile wood (r00.7), before disappearing in the mature wood. These results could be explained by gene pleiotropic effect, low microfibril angle compensating for low wood density and fast growth or by linkage disequilibrium induced by sampling. Variations in MFA and KL in the mature wood were also genetically controlled. & Conclusions These findings provide the opportunity for developing breeding strategies for pulpwood, fuelwood and sawntimber production in Eucalyptus sp. (Résumé d'auteur