Understanding genome differentiation is important
to compare and transfer genomic information between taxa,
such as from model to non-model organisms. Comparative
genetic mapping can be used to assess genome differentiation
by identifying similarities and differences in chromosome
organization. Following release of the assembled Eucalyptus
grandis genome sequence (January 2011; http://www.phyto
zome.net/), a better understanding of genome differentiation between E. grandis and other commercially important
species belonging to the subgenus Symphyomyrtus is
required. In this study, comparative genetic mapping
analyses were conducted between E. grandis, Eucalyptus
urophylla, and Eucalyptus globulus using high-density
linkage maps constructed from Diversity Array Technology
and microsatellite molecular markers. There were 236–393
common markers between maps, providing the highest
resolution yet achieved for comparative mapping in Eucalyptus.
In two intra-section comparisons (section Maidenaria–
E. globulus and section Latoangulatae–E. grandis
vs. E. urophylla), ∼1% of common markers were nonsyntenic
and within chromosomes 4.7–6.8% of markers were
non-colinear. Consistent with increasing taxonomic distance,
lower synteny (6.6% non-syntenic markers) was observed in
an inter-section comparison between E. globulus and E.
grandis×E. urophylla consensus linkage maps. Two small
chromosomal translocations or duplications were identified
in this comparison representing possible genomic differences
between E. globulus and section Latoangulatae species.
Despite these differences, the overall high level of synteny
and colinearity observed between section Maidenaria–
Latoangulatae suggests that the genomes of these species
are highly conserved indicating that sequence information
from the E. grandis genome will be highly transferable to
related Symphyomyrtus species.