Abstract:
Traits that differentiate cross-fertile plant species
can be dissected by genetic linkage analysis in interspecific
hybrids. Such studies have been greatly facilitated in
Eucalyptus tree species by the recent development of
Diversity Arrays Technology (DArT) markers. DArT is an
affordable, high-throughput marker technology for the
construction of high-density genetic linkage maps. Eucalyptus
grandis and Eucalyptus urophylla are commonly
used to produce fast-growing, disease tolerant hybrids for
clonal eucalypt plantations in tropical and subtropical
regions. We analysed 7,680 DArT markers in an F2
pseudo-backcross mapping pedigree based on an F1 hybrid
clone of E. grandis and E. urophylla. A total of 2,440
markers (31.7%) were polymorphic and could be placed in
linkage maps of the F1 hybrid and two pure-species
backcross parents. An integrated genetic linkage map was
constructed for the pedigree resulting in 11 linkage groups
(n=11) with 2,290 high-confidence (LOD≥3.0) markers
and a total map length of 1,107.6 cM. DNA sequence
analysis of the mapped DArT marker fragments revealed
that 43% were located in protein coding regions and 90%
could be placed in the recently completed draft genome
assembly of E. grandis. Together with the anchored
genomic sequence information, this linkage map will allow
detailed genetic dissection of quantitative traits and hybrid
fitness characters segregating in the F2 progeny and will
facilitate the development of markers for molecular breeding
in Eucalyptus.
