Comparative QTL mapping of DBH and wood basic density at four years of age in the E. grandis , E. urophylla and F
hybrid parents of the F
backcross families. Location of putative QTLs associated with DBH (white box) and wood density (black) on linkage group 9 and 10. A major QTL for wood density was found on chromosome 9 in the F1 hybrid in the E. urophylla BC family. Variation in transcript abundance of genes located in the QTL interval, which were also correlated with wood density (Table 4), were explained in part by the presence of shared trans-eQTLs, which co-localized with the wood density QTL on linkage group 10 (white boxes with cross hashing), in addition (for some genes) cis-eQTLs co-locating with the wood density QTL on LG 9 (white boxes with hashing). The backcross and F1 hybrid parental maps are connected by dotted lines through the physical position of the DArT marker fragments in the E. grandis genome sequence (V1.0 assembly, http://www.phytozome.net/). Map positions in centiMorgan (cM Kosambi) and megabase-pair (Mbp) are shown for the genetic and physical maps, respectively. The F1 hybrid maps constructed for the two backcross families are connected through shared testcross markers that segregated in both backcrosses. The position (solid bars, 95% CI; lines, 90% CI) of QTLs detected using composite interval mapping (CIM) are projected onto the genetic maps.