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The application of molecular markers to Eucalyptus globulus tree improvement


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Freeman, Jules Simon 2006 , 'The application of molecular markers to Eucalyptus globulus tree improvement', PhD thesis, University of Tasmania.

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Molecular markers are being applied increasingly to various aspects of tree
improvement. This thesis reports two such applications. The first involves tracing the
natural origins and assessing the genetic diversity of the Portuguese Landrace of E.
globulus, which is a core component of the Portuguese breeding program. In order to
achieve this, variation in chloroplast DNA (cpDNA) sequence and microsatellite
allele frequency in 47 individuals of the Portuguese Landrace were compared with
native stand material. The native gene pool of E. globulus is genetically diverse, with
substantial geographically structured genetic variation in molecular markers, which
makes it possible to trace the origin of germplasm of unknown pedigree, such as the
Portuguese Landrace. Similar affinities suggested by the two independent marker
systems provided strong evidence that the Portuguese Landrace was predominantly
derived from south-eastern Tasmania and to a lesser extent south-eastern Victoria.
Ascertaining the origin of and diversity in such populations will help to avoid
inbreeding and will capture the most favourable traits from native populations when
they are used in breeding programs.
The second application of molecular markers addressed in this thesis involved the
construction of a genetic linkage map and searching for molecular markers
associated with quantitative trait loci (QTL) in E. globulus. This study focussed on
identifying QTL for susceptibility to Mycosphaerella leaf blotch (MLB), a fungal
disease affecting the growth of eucalypt plantations worldwide, and other potentially
correlated traits. In order to search for QTL, parental and consensus linkage maps
were constructed in an F2 inter-provenance cross of Eucalyptus globulus with clonal
replication. The consensus map used for QTL detection contained 169 markers (34
SSR and 135 AFLP loci) in 11 linkage groups. The inclusion of SSR markers
allowed comparison of linkage and QTL information to other mapping and QTL
studies conducted in different mapping pedigrees of E. globulus and other species in
the subgenus Symphyomyrtus. The F2 was genetically variable, with significant
differences detected between genotypes for all recorded traits. Significant QTL were
detected for susceptibility to MLB, herbivory by the autumn gum moth, growth and
vegetative phase change. In the case of MLB susceptibility, two major unlinked QTL explained over 70% of the phenotypic variance. This study reports the first QTL
affecting height to vegetative phase change and disease resistance in E. globulus.
These findings will help to elucidate the genetic control of these complex traits in
Eucalyptus, and provide information that will be useful in attempts to incorporate
them into breeding programs.

Item Type: Thesis - PhD
Authors/Creators:Freeman, Jules Simon
Keywords: Eucalyptus globulus, Eucalyptus globulus, Biochemical markers
Copyright Holders: The Author
Copyright Information:

Copyright 2006 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:

Available for library use only and copying in accordance with the Copyright Act 1968, as amended. Thesis (PhD)--University of Tasmania, 2007. Includes bibliographical references

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