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Quantitative genetics and breeding of Eucalyptus globulus


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Lopez, Gustavo Andres 2002 , 'Quantitative genetics and breeding of Eucalyptus globulus', PhD thesis, University of Tasmania.

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This thesis studies quantitative genetic variation in the forest tree,
Eucalyptus globulus. It examines the effects of inbreeding and
hybridisation on fitness, as well as genetic variation in breeding traits
using an extensive base population and a diallel of intra- and inter-race
reciprocal crosses.
Marked post-zygotic barriers to hybridisation occurred between E.
globulus and E. ovata, with F1 hybrids exhibiting high field mortality.
Inbreeding similarly had deleterious effects, but by 10 years F1 survival
was less than the selfs. Relative hybrid fitness is dependent on
inbreeding levels of parental population. Open-pollinated (OP) progenies
also exhibited growth depression compared with outcrosses, clearly
indicating significant inbreeding is occurring under this mating system.
Genetic variation was examined in a base population of E. globulus
established on four sites in Argentina. This population included OP
progenies from native stands and land races. Thirty variables were
studied, representing growth, bark thickness, form, transition to adult
foliage and Pilodyn penetration, and used to determine population
affinities. Significant genetic differentiation occurred between populations
in most traits. Land races had closer affinities to native stands from
southern Tasmania. Many native populations were superior in growth to
land races, but land races had better form. Significant genetic variation was also detected within E. globulus
populations. Heritabilities were low for forking, survival and form;
intermediate for growth and bark thickness; and high for Pilodyn
penetration and transition to adult foliage. There was strong positive
genetic correlation between the same trait measured at different sites and
ages. Growth traits were genetically independent from other key breeding
Genetic parameter estimates from OP progenies may be biased by
inbreeding depression, as well as specific combining (SCA), maternal and carry-over effects. The effects of such factors on growth were examined
using a diallel mating amongst eight trees from two E. globulus races.
Rapid germination and large seeds resulted in larger seedlings in the
nursery, but these carry-over effects disappeared after two-years field
growth at two Tasmanian sites. Additive and SCA effects were
insignificant at this age, but the interaction between males and females
was significant, with reciprocal inter-race hybrids differing in
performance. Parents differed in chloroplast haplotypes and this is the
first evidence for cyto-nuclear interactions affecting growth of a eucalypt
species. Such reciprocal effects could bias genetic parameters and mean
the cross direction may be important to maximise gains from mass
controlled pollinated seed production systems being developed.

Item Type: Thesis - PhD
Authors/Creators:Lopez, Gustavo Andres
Keywords: Eucalyptus
Copyright Holders: The Author
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Copyright 2002 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, 2003. Includes bibliographical references

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