Abstract
BackgroundEucalyptus is an important genus in industrial plantations throughout the world and is grown for use as timber, pulp, paper and charcoal. Several breeding programmes have been launched worldwide to concomitantly improve growth performance and wood properties (WPs). In this study, an interspecific cross between Eucalyptus urophylla and E. grandis was used to identify major genomic regions (Quantitative Trait Loci, QTL) controlling the variability of WPs.ResultsLinkage maps were generated for both parent species. A total of 117 QTLs were detected for a series of wood and end-use related traits, including chemical, technological, physical, mechanical and anatomical properties. The QTLs were mainly clustered into five linkage groups. In terms of distribution of QTL effects, our result agrees with the typical L-shape reported in most QTL studies, i.e. most WP QTLs had limited effects and only a few (13) had major effects (phenotypic variance explained > 15%). The co-locations of QTLs for different WPs as well as QTLs and candidate genes are discussed in terms of phenotypic correlations between traits, and of the function of the candidate genes. The major wood property QTL harbours a gene encoding a Cinnamoyl CoA reductase (CCR), a structural enzyme of the monolignol-specific biosynthesis pathway.ConclusionsGiven the number of traits analysed, this study provides a comprehensive understanding of the genetic architecture of wood properties in this Eucalyptus full-sib pedigree. At the dawn of Eucalyptus genome sequence, it will provide a framework to identify the nature of genes underlying these important quantitative traits.
Highlights
Eucalyptus is an important genus in industrial plantations throughout the world and is grown for use as timber, pulp, paper and charcoal
wood properties (WPs) vary greatly between species, within species and within a tree and change with age. They can be classified in five categories: i) mechanical properties in response to applied forces, ii) technological characteristics, which are the consequences of the mechanical state of the tree, iii) physical characteristics, corresponding to the natural characteristics of wood which affect mechanical properties, iv) anatomical characteristics, and v) traits related to chemical composition
Variability and correlation between wood properties A total of 201 full-sibs of an interspecific hybrid progeny between E. urophylla and E. grandis were felled at 59 months and used to dissect wood properties
Summary
Eucalyptus is an important genus in industrial plantations throughout the world and is grown for use as timber, pulp, paper and charcoal. WPs vary greatly between species, within species and within a tree (reviewed by Plomion et al [3]) and change with age (reviewed by Raymond [4]) They can be classified in five categories: i) mechanical properties in response to applied forces (e.g. longitudinal growth strain, modulus of elasticity, strength), ii) technological characteristics, which are the consequences of the mechanical state of the tree (e.g. splitting index), iii) physical characteristics, corresponding to the natural characteristics of wood which affect mechanical properties (e.g. wood density, shrinkage), iv) anatomical characteristics (e.g. fibre length, fibre thickness, coarseness), and v) traits related to chemical composition (e.g. cellulose and lignin content, lignin composition). The release of growth stresses during cross-cutting may cause radial cracks at the log end This “end-splitting” phenomenon increases with time according to an asymptotic curve. Lignin content has been reported to be negatively correlated with longitudinal growth strain in Eucalyptus hybrids [8], suggesting a relationship between micro (chemical composition) and macro (mechanical properties) characteristics of wood
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