Effect of genotype by spacing interaction on radiata pine genetic parameters for height and diameter growth

Abstract

Effect of genotype by spacing interaction on radiata pine (Pinus radiata D. Don) height and diameter at breast height (DBH) growth was studied using three spacings (1×1m, 1×2m and 2×3m) and 55 half-sib families in a long-term progeny trial. Examined were the effect of spacing and family on early tree height and diameter growth up to 10years, and on annual ring width (RW) and accumulated DBH of the surviving trees up to age 28years. The effects of spacing on heritability, and age–age genetic correlations were also studied using multiple-year measurements. Spacing had little or limited impact on tree height growth, but a highly significant effect on diameter growth. Spacing also had no significant effect on heritability for tree height, but a very significant effect on the patterns and values of heritability for diameter and DBH growth. Closer spacing was found to depress heritability estimates for DBH. Spacing was also observed to have a significant impact on age–age genetic correlation, and the higher competition level at closer spacing treatment distorted the age–age genetic correlation patterns for DBH due to higher mortality. The spacing effect on heritability was more apparent from early growth measurements due to relatively small mortality compared with the late age measurements. Our current study for the first time revealed significant and useful genotype by spacing interactions in radiata pine for DBH growth. The significant genotype by spacing interactions were mainly caused by a few well-performing families reacting more to spacing changes. Therefore, matching genotype with spacing has the potential to increase productivity of radiata pine plantations.