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MARKER ASSISTED SELECTION
PLANT GENETICS RECITATION
Updated for 2009 based on material prepared by
ALFONSO CUESTA-MARCOS For 2008
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Why marker assisted selection?
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MARKER ASSISTED SELECTION

• Individuals carrying the trait of interest are
  selected based on a marker which is linked to the
  trait and not on the trait itself.
• Indirect selection.
• Useful when the trait is difficult to measure,
  and/or is evident only at late developmental
  stages.

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I I I K I K I I K
iBison 1H4H5H
Kurtford
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The barley stripe rust resistance story 1987
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BARLEY STRIPE RUST
www.barleyworld.org
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BARLEY STRIPE RUST

• Caused by fungus Puccinia striiformis f. sp.
  hordei
• Common in Mexico and South America but usually
  not in Oregon.
• It first appeared in the US in 1991
• When infection is severe, losses of 50 are
  common

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BARLEY STRIPE RUST

• Resistant cultivars are available
• It is necessary to develop resistant cultivars
  adapted to different barley growing areas
• Resistance to the disease is a quantitative trait
  (non-Mendelian inheritance)
• Three Quantitative Trait Loci (QTL) for stripe
  rust resistance have been mapped and their
  effects validated.
• There are molecular markers located in the target
  regions of the three QTL

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Race characterization of BSR isolates from
Huancayo, Peru. 2007
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Cali-sib x Bowman
Shyri x Galena
CI10587 x Galena
BSR-45
D1-72
D3-6
Harrington
Baronesse
Orca
BCD
DB
BCD47
BCD12
D3-6/B23
D3-6/B61
AJO
BU
OPS
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iBISON and BISON
iBISON
BISON
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ORO
OWB Chr. 4H
EBmac701
SSR markers used for MAS
baal29j18

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OWB Chr. 1H
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Unmapped in OWB
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OWB Chrom. 1H
Shyri x Galena
Act8
MWG837
2_0749
2_0749
BCD098
2_0749 Inferred position
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OWB Chrom. 5H
Cali sib x Bowman
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Flanking markers in each target region
Three resistance genes in chromosome 1H, 4H and 5H
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THE PROBLEM

• KURTFORD
• 6 rowed hooded feed barley
• Well adapted to California conditions
• Short height
• Stripe Rust Susceptible

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• iBISON 1H4H5H
• Resistance alleles for the three genes
• 2rowed awned barley short height

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SOLUTION The Kurtford Conversion
Year 1
I Bison 1H 4H 5H
Kurtford 1H 4H 5H
X
SS SS SS
RR RR RR
Kurtford 1H 4H 5H
F1 heterozygote at 3 BSR resistance loci
X
RS RS RS
SS SS SS
BC1F1 12.5 of plants expected to be
heterozygote at 3 BSR resistance loci.
Segregation in each locus ½ RS ½ SS
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Summer Fall 2007

• We have 589 BC1F1 seeds and we expect to find
  around 74 target heterozygotes at the 3 BSR
  resistance loci.We need
• -Confirm choice of markers
• DNA extraction for 589 plants
• Genotyping for the 3 BSR resistance regions
• Selection of targeted genotypes

MAS1
1H
4H
5H
Bmag399 EST4473
EST4535 Baal29j18 . Bags 4e
Bmag337 Bmag223 Bmag812
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I I I K I K I I K
iBison 1H4H5H
Kurtford
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Winter 2008

• Selection of heterozygotes (74)
• 10 seeds per selected plant 740 BC1F2 plants.
• Grow out and genotype

BC1F2 plants segregating in each locus ¼ RR ½
RS ¼ SS
MAS2
We expect 25 of the BC1F2 to be homozygous for
AT LEAST the 4H region ( 185). Of these 104
homozygote only for 4H 35 homozygote for 4H and
1H 35 homozygote for 4H and 5H 11 homozygote
for 1H, 4H and 5H
25/64 ( 38) of the resistant plants will be
homozygous hooded
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Winter 2008/2009 seed increase Summer 2009
validate resistance
Field test
70 homozygous hooded, BSR resistant plants
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Abundant, gene-based markers make MAS more
effective and informative
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What makes a trait quantitative and not
qualitative? Successful MAS may precede gene
characterization Phenotypic performance is the
ultimate measure of agronomic worth
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MAS - coming to a field near you