Genetic parameters for growth, wood density and pulp yield in Eucalyptus globulus |
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Authors: | João Costa e Silva Nuno M G Borralho José A Araújo René E Vaillancourt Brad M Potts |
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Institution: | 1. Centro de Matemática e Aplica??es, Departamento de Matemática, Instituto Superior Técnico, Universidade Técnica de Lisboa, Avenida Rovisco Pais, 1049-001, Lisboa, Portugal 2. Centro de Estudos Florestais, Departamento de Engenharia Florestal, Instituto Superior de Agronomia, Universidade Técnica de Lisboa, Tapada da Ajuda, 1349-017, Lisboa, Portugal 3. RAIZ Forest and Paper Research Institute, Quinta de S. Francisco, Apartado 15, 3801-50, Eixo, Portugal 4. School of Plant Science and Cooperative Research Centre for Forestry, University of Tasmania, Private Bag 55, Hobart, Tas. 7001, Australia
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Abstract: | Genetic variation and co-variation among the key pulpwood selection traits for Eucalyptus globulus were estimated for a range of sites in Portugal, with the aim of improving genetic parameters used to predict breeding values
and correlated response to selection. The trials comprised clonally replicated full-sib families (eight trials) and unrelated
clones (17 trials), and exhibited varying levels of pedigree connectivity. The traits studied were stem diameter at breast
height, Pilodyn penetration (an indirect measure of wood basic density) and near infrared reflectance predicted pulp yield.
Univariate and multivariate linear mixed models were fitted within and across sites, and estimates of additive genetic, total
genetic, environmental and phenotypic variances and covariances were obtained. All traits studied exhibited significant levels
of additive genetic variation. The average estimated within-site narrow-sense heritability was 0.19 ± 0.03 for diameter and
0.29 ± 0.03 for Pilodyn penetration, and the pooled estimate for predicted pulp yield was 0.42 ± 0.14. When they could be
tested, dominance and epistatic effects were generally not statistically significant, although broad-sense heritability estimates
were slightly higher than narrow-sense heritability estimates. Averaged across trials, positive additive (0.64 ± 0.08), total
genetic (0.58 ± 0.04), environmental (0.38 ± 0.03) and phenotypic (0.43 ± 0.02) correlation estimates were consistently obtained
between diameter and Pilodyn penetration. This data argues for at least some form of pleiotropic relationship between these
two traits and that selection for fast growth will adversely affect wood density in this population. Estimates of the across-site
genetic correlations for diameter and Pilodyn penetration were high, indicating that the genotype by environment interaction
is low across the range of sites tested. This result supports the use of single aggregated selection criteria for growth and
wood density across planting environments in Portugal, as opposed to having to select for performance in different environments. |
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Keywords: | Eucalyptus globulus Additive genetic variance Dominance Epistasis Heritability Genetic correlation Linear mixed models |
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