Bayesian analysis of growth, stem straightness and branching quality in full-sib families of Eucalyptus globulus

Freddy Mora,Paulina Ballesta,Nicolle Serra

doi:10.1590/1678-4499.20180317

Abstract

Eucalyptus globulus is one of the most commonly planted hardwood species for industrial use in various temperate regions around the world. The present study aimed to evaluate 62 full-sib families of E. globulus in one of the southernmost progeny trials of the species in the south of Chile. Estimates of genetic parameters for stem straightness, branching quality and growth traits were based on a Bayesian modelling approach using Gibbs sampling. A Bayes Factor (BF) analysis supported the hypothesis of significant additive genetic variation for all traits under study. Conversely, the BF supported a model with significant dominance effects for the diameter at breast height and stem volume, which explained up to 25% of the phenotypic variation. The greatest narrow-sense heritability estimates were found for the tree height and stem straightness, which were 0.15 (0.08 to 0.26) and 0.18 (0.10 to 0.28), respectively (mean of posterior distributions and 90% credible sets). In turn, the branching quality had a low heritability (narrow-sense) that varied from 0.05 to 0.10 (90% Bayesian credible region). The mean posterior estimate of genetic correlation between both quality traits was 0.22 (0.01 to 0.63, 90% credible set from a bi-trait threshold model), which indicates that stem straightness is positively related to branching quality. Our findings reveal that the study population responds to common patterns of breeding populations of E. globulus. This information is valuable for the development of improved seeds in the southern zone of Chile.

Highlights

Trees of the genus Eucalyptus L’Hér. are recognized for their high biomass production, rapid growth rate, good adaptation to diverse environmental conditions and excellent wood quality for the production of paper and products derived from solid wood (Schmit et al 2015; Mora and Arriagada 2016)
E. globulus has been positively grown in a widespread range of environmental conditions that are adverse for plant establishment (Dutkowski and Potts 1999; Tibbits et al 2006)
The mean posterior estimate of genetic correlation between both timber quality traits was 0.22 (0.01 to 0.63, 90% credible set for the threshold model), which indicates that stem straightness is positively related to branching quality

Summary

Introduction

Trees of the genus Eucalyptus L’Hér. are recognized for their high biomass production, rapid growth rate, good adaptation to diverse environmental conditions and excellent wood quality for the production of paper and products derived from solid wood (Schmit et al 2015; Mora and Arriagada 2016). E. grandis, E. urophylla and E. globulus are the most commonly planted hardwood species for industrial uses in tropical (or subtropical) and temperate zones, respectively (Carocha et al 2015; Quang et al 2010). They stand out as the targets of multiple breeding programs and silvicultural management (Rosado et al 2010; Carocha et al 2015; Carbonari et al 2016). In Chile, several studies have been focused on the mechanisms through which E. globulus trees respond to abiotic stresses (e.g. Navarrete-Campos et al 2013; 2017; Aguayo et al 2016)

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Results

Conclusion