QTL influencing growth and wood properties in Eucalyptus globulus

Abstract

Regions of the genome affecting physical and chemical wood properties (quantitative trait loci (QTL)), as well as growth, were identified using a clonally replicated, outbred F 2 family (112 genotypes, each with two ramets) of Eucalyptus globulus, planted in a field trial in north-west Tasmania. Traits studied were growth (assessed by stem diameter), wood density, cellulose content, pulp yield and lignin content. These traits are important in breeding for pulpwood, and will be important in breeding for carbon sequestration and biofuel production. Between one and four QTL were located for each trait, with each QTL explaining between 4% and 12% of the phenotypic variation. Several QTL for chemical wood properties were co-located, consistent with their high phenotypic correlations, and may reflect pleiotropic effects of the same genes. In contrast, QTL for density and lignin content with overlapping confidence intervals were considered to be due to independent genes, since the QTL effects were inherited from different parents. The inclusion of fully informative microsatellites on the linkage map allowed the determination of homology at the linkage group level between QTL and candidate genes in different pedigrees of E. globulus and different eucalypt species. None of the candidate genes mapped in comparable studies co-located with our major QTL for wood chemical properties, arguing that there are important candidate genes yet to be discovered.

Quantitative trait locus analysis of leaf morphological characters, yield-related traits, and secondary metabolite contents in Eucommia ulmoides

“…Furthermore, the clustering of QTLs controlling height and basal diameter has been observed in the same mapping population of E. ulmoides (Li et al, 2014c). In most cases, no clear patterns among phenotypic correlations have been found to coincide with the co-locating QTLs (Tsarouhas et al, 2002;Gailing, 2008;Freeman et al, 2009;Thumma et al, 2010;Li et al, 2014c). In the present study, we found that 16 QTLs were unique to specific traits (Figure 2).…”

“…Previous QTL studies on main crops have frequently detected regions of the genome that contain clusters of QTLs for highly correlative traits (Zeng et al, 2009;Avia et al, 2013;Bian et al, 2013). Clusters of QTLs were also observed for growth traits and various leaf traits in poplar (Bradshaw and Stettler, 1995;Wu et al, 1997), for wood properties and growth traits in the genus Eucalyptus (Verhaegen et al, 1997;Freeman et al, 2009;Thumma et al, 2010), for growth traits in Salix (Tsarouhas et al, 2002;Ronnberg-Wastljung et al, 2005), for leaf morphological characters in European beech (Scalfi et al, 2004) and oak (Gailing, 2008;Gailing et al, 2013), and for chemical compositions in peach (Eduardo et al, 2013) and oil palm (Montoya et al, 2013). Furthermore, the clustering of QTLs controlling height and basal diameter has been observed in the same mapping population of E. ulmoides (Li et al, 2014c).…”

“…The genetic information acquired by QTL analysis, including the number, location, and magnitude of effects of genetic regions associated with a trait, also contributes to our understanding of the genetic basis of economically important traits. In tree species, QTL analyses have been reported for leaf traits and chemical constituents in European beech (Scalfi et al, 2004), oak (Gailing et al, 2013), Eucalyptus (Freeman et al, 2009), peach (Eduardo et al, 2013), and oil palm (Montoya et al, 2013). In contrast, QTLs affecting leaf morphology characters, yield-related traits, and secondary metabolite contents have not been reported in E. ulmoides.…”

Lineage-specific mapping of quantitative trait loci

“…It is mainly applied to gene sequences and gene products (Fitch, 2000;Petsko, 2001). Homology of QTL has been classically defined as QTL that map to the same position in different populations or species (for example, see Freeman et al, 2009). In lineage-specific QTL mapping, we can subdivided homology into 'orthology of QTL' , as QTLs that share common ancestry (share the same mutational event of an ancestor), and 'paralogy of QTL' , as QTLs that have different mutations in the same region of the genetic map, but which arise independently.…”

Transferability of microsatellite markers located in candidate genes for wood properties between Eucalyptus species

“…However, only few studies in most widely cultivated species of Eucalyptus have analyzed CGs underlying wood quality traits using QTL approaches (Freeman et al, 2009;Thumma et al, 2010;Gion et al, 2000Gion et al, , 2011. The use of already well-established variable markers present in CGs for wood quality is an interesting approach for mapping purposes and functional diversity studies.…”