EXPLORATION OF THE EUCALYPTUS GLOBULUS GENE POOL

Abstract

The first Europeans to discover Eucalyptus
\nglobulus were French explorers in 1792. Its seed
\nwas rapidly spread throughout the world in the
\n19th century and this was the species by which
\nmuch of the world first knew the genus.
\nHowever, it was in the industrial forests of the
\n20th century that this species, once considered
\nthe ‘Prince of Eucalypts’, achieved greatest
\nprominence due to its fast growth and superior
\npulp qualities. Formal breeding first commenced
\nin 1966 in Portugal and in the late 1980’s large
\nbase population trials from open-pollinated seed
\ncollections from native stands were established
\nin many countries. These trials have provided
\nunprecedented insights into the quantitative
\ngenetic control of numerous traits of economic
\nand ecological importance and how this variation
\nis spatially distributed in the native range of the
\nspecies. However with large, fully pedigreed
\nbreeding populations becoming available for
\nquantitative analysis and the rapidly expanding
\nknowledge of DNA sequence variation, we are
\nnow at the threshold of a new understanding of
\nthis important eucalypt gene pool. Indications of
\nthe significance of non-additive genetic effects
\nare becoming available. The E. globulus
\nchloroplast genome has now been sequenced
\nand several genome maps have been published.
\nStudies of the variation in nuclear microsatellites
\nand the lignin biosynthesis gene CCR confirm
\nthe complex, spatially structured nature of the
\nnative gene pool. Strong spatial structuring of
\nthe chloroplast genome has provided a tool for
\ntracking seed migration and the geographic
\norigin of exotic landraces. Highly divergent
\nlineages of chloroplast DNA have been
\ndiscovered and studies of the hypervariable JLA+
\nregion argue that some components of the E.
\nglobulus gene pool have been assimilated from
\nother species following hybridisation.