The objective of this study was to determine the genetic location and effec
ts of genomic regions controlling wood density at three stages, i.e., rings
corresponding to ages 1-5 (WD1-5), rings corresponding to ages 6-10 (WD6-1
0), and outer wood density (WD14) in a full-sib pedigree (850.055x850.096)
of Pinus radiata . The number of offspring measured at these three stages w
ere 80, 93 and 93, respectively. Only a single linkage group of the parent
850.55 was considered for mapping quantitative trait loci (QTLs). A multipl
e-marker least-squares approach was employed for mapping QTLs for each of t
he three traits, using a single-QTL model. Logistic regression was used for
multiple-trait QTL mapping. Critical values for test-statistic were calcul
ated empirically by 'shuffling' the data. A putative QTL with large effect
on WD1-5 appears to be segregating at the 73 cM position (experimentwise P<
0.01). The width of the 95% bootstrap confidence interval for this putative
QTL was 40 cM (i.e. 56-96 cM). The effect of this QTL on the expression of
wood density at later stages was diminished. From multiple-trait analysis,
two marker locations (at 66 cM and 91 cM) were found to be significantly a
ssociated (experimentwise P <0.05) with the expression of wood density at d
ifferent ages. These results are encouraging for the application of marker
information to early selection in order to increase juvenile wood density,
although the putative QTLs detected in this study need to be verified in an
independent population.