Abstract
The aim of this study was to determine genetic parameters for straightness of the trunk of Eucalyptus cladocalyx, with a view to the selection of straight trees, while keeping the impact on growth minimal. The tests were conducted at two locations in the semi-arid region of Chile, using a randomized block design, with 30 replications and 49 half-sib families. The parameters were estimated by a bi-character model of individual trees, using Bayesian inference by Gibbs algorithm. The heritability for stem straightness was shown to be moderate, with h2=0.40 [0.29-0.57]. Heritabilities for diameter and height were moderate: 0.30 [0.24-0.38] and 0.30 [0.22-0.44]. Genetic correlations between straightness and growth were statistically not different from zero. The genotype-environment interaction was not significant (p>0.05) for the traits. The moderate degree of genetic control allows significant genetic gains in environments under water stress.
Highlights
The genus Eucalyptus, with over 700 species, is native to Australia and adapted to various ecosystems, from tropical regions with abundant rainfall to semi-arid areas with prolonged dry periods, demonstrating the potential for cultivation under different environmental conditions (Ladiges et al 2003, Grattapaglia and Kirst 2008)
Significant differences were found between populations for the traits stem straightness and growth (Table 1)
The best stem straightness was found in a population from Illapel, Chile; followed by Wirrabara (2.24) and Remarkable (2.17)
Summary
The genus Eucalyptus, with over 700 species, is native to Australia and adapted to various ecosystems, from tropical regions with abundant rainfall to semi-arid areas with prolonged dry periods, demonstrating the potential for cultivation under different environmental conditions (Ladiges et al 2003, Grattapaglia and Kirst 2008) In this sense, Eucalyptus cladocalyx is a species that grows naturally in the semi-arid zone of South Australia, in the regions of Kangaroo Island, Flinders Ranges and Eyre Peninsula (Brooker and Kleinig 1999, Mcdonald et al 2003), and is adapted to average rainfall levels of 400 to 600 mm per year (Blakemore 2004, Callister et al 2008). The wood of sugar gum has extraordinary resistance, durability and high density (Blakemore 2004, Callister et al 2008) This product is result of the selection of trees with improved growth traits (e.g., straightness), to produce poles for agriculture (Mora et al 2009, Bush et al 2011). The conservation of the genetic diversity and heterozygosity in allogamous species such as Eucalyptus can maintain the possibility of permanent genetic gains over time (Danusevicius and Lindgren 2002)
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