steptoe x morex - the weakest link? - hutton
TRANSCRIPT
Steptoe x Morex – the weakest link?L Ramsay1, R Waugh1, D Marshall1, T Close2, G Young1, R Keith1 & W Thomas1
1SCRI, Invergowrie, Dundee DD2 5DA, UK; 2UCR, University of California, Riverside, CA 92521-0124, USA
Conclusions
Despite the major genes segregating in
both crosses, we were able to detect
some evidence of co-location of QTLs
for the same trait in the different crosses
but, despite the common environments
and marker assays, most of the
locations are cross-specific. Indeed, for
yield in SxM, many of the QTLs are
associated with various parameters of
harvest loss (see photographs), which
emphasise the need to work with the right
germplasm for the target environment.
Results
A third of the BOPA1 SNPs were polymorphic in DxB compared to just over
a half in SxM. Nevertheless, the DxB data enabled the location of just over a
third of the previously unmapped BOPA1 SNPs. In general, both populations
spanned similar genomic regions – DxB lacked coverage of the first 2 bins
and the first bin on chromosomes 2H and 5H respectively. SxM lacked
coverage on the last 7 bins of chromosome 6H and DxB had a completely
different haplotype on the long arm of 4H (Figure 1).
Over 100 bin x trait locations were detected over
the two crosses but there were only six instances
of the same trait being located in the same bin for
both crosses, although there were some in
adjacent bins (Figure 2). The co-locations were
for TGW in bin 5 and bin 7 on chromosomes 2
and 7H respectively, for yield in bin 10 on 4H, for
heading date and milling energy in bins 4 and 6
respectively on 7H and for grain width:length ratio
in bin 6 of 4H.
Materials & Methods
DH populations from SxM and DxB were grown at SCRI in each of harvest years
2002-4 inclusive, with each being sown on the same date and given the same
management regime. Plots were scored for heading date and height and harvested
when ripe to assess plot yield.
Cleaned and sieved samples were used to measure thousand grain weight (TGW by
MARVIN digital analyzer) and hardness (by Comparamill). The DxB population was
genotyped with the Illumina BOPA1 SNPs and a fresh marker map constructed that
included several key major genes. The SxM population had been genotyped with
pilot OPA1 and 2, data from which was used to construct BOPA1. We therefore
extracted the BOPA1 equivalent SNP polymorphisms from the pilot OPA1 & 2 data
to construct a new SxM map that was directly comparable to the DxB map.
Little spatial variation was apparent in the trials and so the unadjusted scores from
each trial in each year were used in QTL detection. QTL locations were then
referenced to the SxM bin map to compare locations.
AcknowledgementsWe thank the Scottish Government for their financial support of this work.
Whilst many single cross QTL studies have been conducted,
there are few examples that have compared the results from
two different crosses grown in the same environment and
with the same marker assay. Two of the most widely studied
barley crosses in QTL analyses are DH populations from
Steptoe x Morex (SxM), representing adapted North West
American germplasm, and Derkado x B83-12/21/5 (DxB),
representing adapted North West European germplasm.
The advent of the Illumina SNP genotyping platform means
that we can now readily generate marker maps from the
same platform and, given trials grown in the same
environment, compare results.
Introduction
1
Hor22
Hor1
34
5
6
78
Glb1
9
10
11
12
13
14
1H
1
2Ppd1
3
4
5
67
89
Vrs1
10
11
12
13
14
15
2H
1
2
3
4
5
6
78
9
10
11sdw112
13
14Glb4
15
16
3H
1
23
4Dhn6
5RubA
6
7
8
9
mlo10
11Vrn212
Bmy113
4H
1
23
45
ari-e
6
7
8
9
10
Vrn111
12
13
14
15
5H
1
2
34
5
6
7
8Amy1
9
10
111213
14
6H
1Wx
2
3
4
5
6
7Amy2
8
9
10
11
12
7H
16
1
Hor22
Hor1
34
5
6
78
Glb1
9
10
11
12
13
14
DxB
SxMDxB
SxMSxM
SxMSxM
1H
1
2Ppd1
3
4
5
67
89
Vrs1
10
11
12
13
14
15
SxMDxB
SxMSxM
DxB
DxB
SxM
SxMDxB
SxMDxB
SxMSxM
SxMDxB
SxMDxB
SxMSxM
2H
1
2
3
4
5
6
78
9
10
11sdw112
13
14Glb4
15
16
DxB
SxMDxB
SxMSxM
DxB
DxB
DxB
DxB
SxMSxM
SxMDxB
DxB
DxB
DxB
DxB
DxB
3H
1
23
4Dhn6
5RubA
6
7
8
9
mlo10
11Vrn212
Bmy113
SxMSxM
DxB
SxM
SxMDxB
SxMDxB
SxM
4H
1
23
45
6ari-e7
8
12
13
14
15
SxMDxB
SxMDxB
SxMDxB
SxMDxB
SxMDxB
SxM
DxB
DxB
5H
1
2
34
5
6
7
8Amy1
9
10
111213
14
DxB
DxB
SxMSxM
DxB
SxMSxM
SxM
6H
1Wx
2
3
4
5
6
7Amy2
8
9
10
11
12
DxB
SxMSxM
DxB
SxMSxM
DxB
SxMDxB
SxMDxB
SxMSxM
DxB
SxMSxM
SxMDxB
DxB
SxM
7H
Heading Date
Milling Energy
Width:Length
Height
Yield
TGW
Acknowledgements
DxB
SxM
t A
We ththeir f
12
13
14
15
DxB
DxB
SxM
8Amy1
9
10
111213
14
DxB
7Amy2
8
9
10
11
12
SxMSxM
DxB
ng Date
g Energy
Length
A
White: Not polymorphic in DxBRed: Not polymorphic in SxMGreen: Different haplotypes