Efficiency of early selection for rotation-aged growth and wood density traits in 'Pinus radiata'

Abstract

A total of 1097 cross-sectional wood disks from breast height were sampled from two rotation-aged (27 and 31 years from planting) genetic trials of radiata pine ('Pinus radiata' D. Don) in Australia to estimate the genetic correlation between early and rotation-aged growth and wood quality traits and the efficiency of early selection. Annual growth-ring width and density, diameter at breast height (DBH), and area-weighted density (AD) from 30 open-pollinated families were measured using X-ray densitometry. Genotype × site interactions were not significant for density and growth traits. Ring density increased steadily from the pith to cambial age 14, and then density had little change in the following years. For AD, the family and individual heritability estimates were about 0.60 and 0.30 after the first 2 years. For DBH, family and individual narrow-sense heritability estimates increased steadily after the first 4 years, and family heritability increased to 0.7 at a cambial age of 11 and had little change thereafter. Individual heritability estimate increased to 0.4 at cambial age 14 and was similar for the later ages. Beyond a cambial age of 5 years, there were strong negative genetic correlations of around –0.80 between AD and DBH. Age–age genetic correlations for AD were high and reached 0.80 and above after cambial age 3. Age–age genetic correlations for DBH were similar to AD, except the first two years. The most efficient early selection year was between ages 4 and 6 years after planting for AD, and between ages 8 and 11 years for DBH.