Wood basic density is among the selection
criteria for many fast-grown tree species, including
Pinus radiata D. Don in New Zealand. Basic density
was assessed in 23,330 stem cores from 18 trials to
study the heritability, the relevance of environmental
effects and the magnitude of genotype-by-environment
(GxE) interaction. Site differences in annual average
temperature dominated variability in this dataset, with
lower latitude and altitude (i.e. warmer) sites displaying
higher average density. Between highest- and lowestdensity
sites there was an 18% difference (302.7 vs.
358.4 kg m-3) for the linear mean for cores of rings 1–5
and a 39% difference (329.7 vs. 459.1 kg m-3) for the
linear mean of rings 6–10. The estimated heritabilities
fluctuated between 0.28 and 0.94 (mean, 0.6); however,
basic density displayed little within-site variability
(phenotypic coefficient of variation, <8%). Bivariate
analyses were used to estimate between-site genetic
correlations as an indication of GxE interaction. Only
57 out of the 153 pairs of trials contained enough
information to estimate the between-site genetic correlations
and, out of those, 15 estimates were not
statistically significant. Moderate to high (0.46–0.96)
significant genetic correlation estimates indicated that
there was little interaction for basic density, suggesting
no need to modify the breeding strategy to account for
differential performance in this trait. Poor connectedness
between trials could be depressing estimates of
genetic correlations. This situation should be considered
when designing genetic testing schemes, particularly
when purposely inducing imbalance as in rolling
front strategies
