Clonal stability in Pinus radiata across New Zealand and Australia. I. Growth and form traits

To investigate genotype by environment interaction (GxE) for clones of radiata pine (Pinus radiata), clonal stability was evaluated for growth and form traits from three trials in New Zealand and three trials in Australia. There were 215-245 clones in common between pairs of New Zealand trials, 17-26 clones in common among Australian trials, while 32-52 clones were in common between New Zealand and Australian sites. Clonal repeatability ((H) over cap (2)) and type-B genetic correlations were estimated. The general trend across the six trials for clonal repeatability was that (H) over cap (2) was greatest for height (HGT) followed by diameter at breast height (DBH), stem straightness (STR), and branch quality score (BRQ). Within New Zealand trials, there was little evidence of GxE for growth traits, but more for form traits. For DBH the average type-B genetic correlation within New Zealand was 0.82; and for HGT, the average type-B genetic correlation within New Zealand was 0.76. Within Australia, there was only one statistically significant type-B genetic correlation for DBH and this estimate was high indicating that clonal ranks were similar on these two trials. Additionally, within Australia and between regions type-B genetic correlations were generally high for form traits, at least for STR. One Australian trial (Trial 5) showed relatively high clonal stability with the three trials in New Zealand indicating that the ranks of these clones were relatively stable in both regions. From a clonal testing standpoint, these results suggest that stable clones can be identified that perform well in both New Zealand and Australia. Improvements in both growth and form traits can be expected when radiata pine clones are transferred between Australia and New Zealand within regions similar to those sampled in this trial series.