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Genetic parameters for lignin, extractives and decay in Eucalyptus globulus

http://dx.doi.org/10.1051/forest:2006080

ABSTRACT Eucalyptus globulus is grown in temperate regions of the world for pulp production. The chemical and physical properties of its wood make it highly suited to this purpose. This study analysed genetic variation in lignin content, extractives content and decay, for nine localities of E. globulus. Heritability estimates were also obtained, and the relationships between these traits and physical wood traits and growth were examined. Significant genetic variation was found between localities for lignin content (Klason lignin and acid-soluble lignin contents) and decay. The only trait for which significant variation between families within locality was detected was acid-soluble lignin content, which resulted in this trait also having the highest narrow-sense heritability ($0.51 \pm 0.26$). However, family means heritabilities were high for lignin content, extractives content and decay (0.42–0.64). The chemical wood traits were strongly correlated with each other both phenotypically and genetically, with important correlations found with density and microfibril angle. Correlations suggested that during selection for the breeding objective traits, it is likely that favourable states in the chemical wood traits, decay resistance and fibre properties are concurrently being selected, whereas growth may be selected for independently. This initial study provides a stepping stone for future studies where particular localities of the breeding population may be characterised further. Paramètres génétiques pour la lignine, les extractibles et la pourriture chez Eucalyptus globulus. Eucalyptus globulus est cultivé dans de nombreuses régions tempérées pour la production de pâte à papier. Les propriétés physiques et chimiques de ce bois en font un matériau très apprécié pour cette utilisation. Cette étude analyse les variations génétiques de la teneur en lignine, en composés extractibles et de la sensibilité à la décomposition du bois de neuf provenances de Eucalyptus globulus. L'héritabilité de ces propriétés ainsi que leurs relations avec les caractéristiques physiques du bois et la croissance ont été examinées. Des différences inter-provenances significatives ont été détectées pour les teneurs en lignine (lignines dosées par la méthode de Klason, ou lignines soluble en solution acide) et la vitesse de décomposition. Le seul caractère qui a présenté une variation significative entre familles dans les provenances a été la teneur en lignines solubles en solution acide. De ce fait, une forte héritabilité (au sens strict) a été détectée pour ce caractère ($0,51 \pm 0,26$). Cependant, les héritabilités moyennes dans les familles étaient élevées pour la teneur en lignine, les teneurs en composés extractibles et la vitesse de décomposition (0,42–0,64). Les caractéristiques chimiques du bois étaient fortement inter-corrélées au niveau phénotypique et génétique, avec des corrélations importantes également avec la densité et l'angle des microfibrilles. Les corrélations suggèrent que durant la sélection de caractères objectifs d'amélioration, des traits favorables associant caractéristiques chimiques du bois, résistance à la décomposition et propriétés des fibres puissent être sélectionnés simultanément, alors que la croissance doit faire l'objet d'une sélection indépendante. Cette étude constitue une base pour de futurs travaux permettant une caractérisation plus fine de provenances particulières dans cette population de sélection.

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