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Genetic Mapping of Powdery
Mildew Resistance Genes in Wheat
Ainong Shi
Advisors: Steven Leath, and Paul Murphy
North Carolina State University
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Wheat
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Wheat powdery mildew (Blumeria graminis f. sp. tritici)
is a disease of major importance.
The use of single gene resistance is the primary method of control
of this disease. Identification of molecular markers and genetic
mapping can provide a tool for marker assisted breeding.
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Objective
Identify molecular markers
 Genetic mapping of genes for
powdery mildew resistance in wheat

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Genetic mapping procedure
Phenotype Evaluation
Primer Screening
Linkage Analysis
Genetic Map
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An example
Identification and mapping of Pm25 gene
for wheat powdery mildew resistance
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(R)
(S)
Coker 68-15
x NC96BGTA5
F1 x Coker 68-15
X
F2
BC1F1
Obtaining segregating populations for genetic analysis
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Detached leaf technique
An example of detached leaf technique for reactions to powdery mildew in a F2
population. The culture dish contains 35 primary leaf segments from 35 F2 plants of a
Coker 68-15/NCBGTA5 F2 population and six leaf segments from susceptible Check
Chancellor on the each side.
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Assessment of Reaction to Powdery Mildew
0
1
2
3
4
5
6
7
8
9
A scale of 0 to 9
• Resistant: 0-3
• Intermediate: 4-6
• Susceptible: 7-9
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Reactions to isolate 209a2 of Bgt in Coker 68-15/NCBGTA5 F2
and Coker 68-15*2/NCBGTA5 BC1F1 populations
Res. Sus. Exp.
c2
Gene
-------------------------------------------------------------------------F2
189
77
3:1
2.210 Pm25
BC1F1
55
52
1:1
0.08
50
45
40
35
F2
30
25
209a2
20
15
10
5
Infection type
0
0
Frequency
1
2
3
4
5
6
7
8
9
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Primer Screening
• Method: Bulked segregant analysis (BSA)
• Segregating population: Coker 68-15*2/NCBGTA5 BC1F1
• R bulked from 30 high resistant plants
• S bulked from 30 high susceptible plants
• A total of 156 ten-base random primers
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An example for BSA
Amplification pattern from RAPD
marker OPX061050 for Pm25 in four
wheat materials:
1. Coker 68-15 (None),
2. NC96BGTA5 (Pm25),
3. S bulked (None),
4. R bulked (Pm25),
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Amplification pattern of DNA detecting OPX061050, OPAG04950, and OPAI14600 RAPD fragments in
the Coker 68-15*2/NC96BGTA5 BC1F1 population. Lane 1 to 5 from susceptible plants and lane 6
to 11 from resistant plants with lane 1 and 7 indicating recombinants.
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_______________________________________________
Rec
Dist
Marker
Frac
cM
id
Name
_______________________________________________
(4.2%)
(4.2 %)
(4)
OPAI14600
(2)
OPX061050
(3)
OPAG04950
(1)
Pm25
4.4
4.4
(11.3 %) 12.8
A genetic map of the region carrying Pm25 constructed 14
from the Coker 68-15*2/NC96BGTA5 BC1F1 population
Another example
Mapping Pm3b gene for resistance
to wheat powdery mildew
•
•
Method: NILs
Linkage analysis: F2 seg.
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OPAN07
1 2 3 4 5
6 7
Amplification patterns of DNA from seven
‘Chancellor’ near-isogenic lines with
random primers.
1400-bp
1.
Chancellor (Cc, recurrent parent),
2.
Axminister/8*Cc (Pm1),
3.
Ulka/8*Cc (Pm2),
4.
Asosan/8*Cc (Pm3a),
5.
Chul/8*Cc (Pm3b),
6.
Sonora/8*Cc (Pm3c),
7.
Khapli/8*Cc (Pm4a).
A total of 332 random Operon primers were used to
screen for RAPD markers in the seven ‘Chancellor’
near-isogenic lines.
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Chancellor//Chul/8*Cc F2
Isolate
Res. Sus. Exp.
c2
E314
61
22
3:1
0.100
------------------------------------------------------Frequency
25
20
15
E314
10
5
0
0
1
2
3
4
5
6
7
8
9
Infection type
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1400bp
1400bp
Amplification pattern of DNA detecting OPAN071400 RAPD fragments from the F2
population of Chancellor//Chul/8*Cc. PS=susceptible parent, PR=resistant parent,
S=Susceptible individual in the F2 and R=resistant individual in the F2. Lane M is a
1-kb molecular-weight marker.
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Co-segregation of reaction of Pm3b to E314 isolate of Bgt and RAPD
marker OPAN071400 in the Chancellor/(Chul/8*Cc) F2 population.
________________________________________________________
Locus
Phenotype
c2A
c2B
c2AB Recombination
A
B
RM* Rm SM Sm (3:1) (3:1) (9:3:3:1) fraction
Pm3b AN071400 61 0 1 21 0.100 0.004 81.776** 1.2
________________________________________________________
* RM = resistant plant with the marker, Rm = resistant without the marker,
SM = susceptible with the marker, and Sm = susceptible without the maker.
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1.2
Pm3b
OPAN071400
Linkage distance
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SUMMARY
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Sixteen RAPD markers linked to Pm1, Pm3b, Pm12,
Pm21, Pm25, pmTD1 and Pm3 locus.
Gene
RAPD marker
Pm1
OPU17750
Pm3b
OPAN071400
Pm12
OPAE121350, OPAE12495
OPAH05580, OPAI13490
Pm21
OPAN031700, OPAI01700, OPAL03750
Pm25
OPAI14600, OPX061050, OPAG04950
pmTD1
OPQ09750
Pm3 locus
OPS031400, OPN09600, OPN091200
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_______________________________________________
Rec
Dist
Marker
Frac
cM
id
Name
_______________________________________________
(4.2%)
(4.2 %)
(4)
OPAI14600
(2)
OPX061050
(3)
OPAG04950
(1)
Pm25
4.4
4.4
(11.3 %) 12.8
A genetic map of the region carrying Pm25 constructed
from the NK-68-15*2/NC96BGTA5 BC1F1 population
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2.2
1.6
Pm1
OPU17750
OPAI13490
OPAE12495
3.3
1.6
1.2
Pm3b
OPAN071400
Pm3
3.2
OPAH05580
Pm12
3.3
0.0
1.0
OPN09600, OPN091200
OPS031400
OPAE121350
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ACKNOWLEDGEMENTS
North Carolina State University:
Dr. Steven Leath, Dr. J. Paul Murphy,
Dr. Martin L. Carson, Dr. Ben-Hui Liu, and
Dr. Rebeca C. Rufty.
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Thank you!
Thank all of
you!
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