Résumé
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. To determine the narrow-sense heritability estimates (h (2)) 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. Heritability and correlations were assessed in 340 control-pollinated progenies of 14-year-Eucalyptus urophylla S.T. Blake using near infrared spectroscopic models. Moderate to high heritability were found for MFA (h (2) = 0.43), D (h (2) = 0.61), S/G (h (2) = 0.71) and LK (h (2) = 0.76). The genetic control of D and MFA and the genetic and residual correlation between chemical and growth traits varied with age. The genetic correlation C x D was always strongly negative (r < -0.80) while the correlation D x MFA remained constant and positive in the juvenile wood (r = 0.7), 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. These findings provide the opportunity for developing breeding strategies for pulpwood, fuelwood and sawntimber production in Eucalyptus sp.