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

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.

摘要 蓝桉（Eucalyptus globulus）是全球众多温带地区最常用于工业用材的阔叶树种之一。本研究旨在智利南部该物种最南端的子代测定试验之一中，评估62个蓝桉全同胞家系。针对树干通直度、分枝品质及生长性状的遗传参数估计，采用基于吉布斯抽样的贝叶斯建模方法开展。贝叶斯因子（BF）分析证实，所有受试性状均存在显著的加性遗传变异。与之相反，贝叶斯因子支持胸径和材积存在显著显性效应的模型，该效应可解释高达25%的表型变异。树高和树干通直度的狭义遗传力估计值最高，分别为0.15（90%可信集：0.08~0.26）与0.18（90%可信集：0.10~0.28），均为后验分布均值。分枝品质的狭义遗传力较低，介于0.05~0.10之间（90%贝叶斯可信集）。通过双性状阈值模型得到的两类品质性状间遗传相关的后验均值估计值为0.22（90%可信集：0.01~0.63），表明树干通直度与分枝品质呈正相关。本研究结果表明，试验群体符合蓝桉育种群体的普遍规律。该研究成果对智利南部地区的林木改良种子培育具有重要参考价值。