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Abstract

Eucalyptus nitens is a hardwood plantation species used in cool-temperate regions
of the world. It is mainly used for pulp and paper, although there is increasing
interest in using this species for producing high quality appearance and structural
timber products. Therefore breeding programs need to consider the requirements
of different markets and breed for a variety of end-uses.
The aim of this thesis is to study the genetic control of E. nitens wood properties.
The focus is on three different product groupings which are pulp and paper,
appearance grade timber, and structural grade timber. Pulp and paper traits
studied were wood density, cellulose content, fibre length and fibre coarseness;
appearance grade timber traits were collapse, checking and decay; and structural
grade timber traits were stiffness and microfibril angle.
Genetic parameters and potential genetic gains were estimated using data from 12
year old E. nitens progeny trials grown on three sites. Wood properties were
sampled using 12 mm cores taken at a height of approximately 1 metre.
Relationships between whole tree wood density and core wood density, and whole
tree pulp yield and core cellulose content were investigated. For both traits core
samples were good predictors of whole tree values. Methods were developed to
assess wood collapse and decay using wood cores.
All wood properties except fibre coarseness had significant genetic variation, with
heritabilities ranging from 0.38 to 0.56. The heritability for stem diameter was
0.39. Genetic correlations between traits were mostly significant and reasonably
high. Adverse correlations occurred between diameter and density, diameter and
collapse, diameter and stiffness, and between density and cellulose. Favourable
correlations occurred between diameter and cellulose, density and collapse and
between density and stiffness. Genotype by environment interactions were
sometimes present but were always small.
Genetic selection can significantly improve the quality of wood produced for pulp
and paper, appearance grade timber and structural grade timber. Of particular
importance are the potential gains in collapse (or checking) and stiffness, where
genetic selection can potentially lift the quality grades of appearance and
structural products. Selecting a deployment population for high decay resistance
may minimise the risk of value loss on sites known to have severe decay
problems. Breeding goals for all product groupings are reasonably well correlated
and improved product quality can be achieved in all product groupings without
the need for specialised breeds. Selecting for wood density, as well as growth
rate, is a minimum requirement if high grades of timber are to be produced.

Item Type:	Thesis - PhD
Authors/Creators:	Kube, Peter Denis
Keywords:	Eucalyptus, Eucalyptus
Copyright Holders:	The Author
Copyright Information:	Copyright 2005 the Author - The University is continuing to endeavour to trace the copyright owner(s) and in the meantime this item has been reproduced here in good faith. We would be pleased to hear from the copyright owner(s).
Additional Information:	Thesis (Ph.D.)--University of Tasmania, 2005. Includes bibliographical references
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