1. Borlaug Global Rust Initiative Technical Workshop – 2014
Session: “Rust Resistance in Tetraploids”
Ciudad Obregon, March 23, 2014
Advances
in Breeding for Resistance to Stem Rust
Caused by Ug99 and Ethiopian Pgt Races in
Durum Wheat
Ayele Badebo
DZARC – EARO, Ethiopia
Karim Ammar, Abeyo Bekele, Alexandro Loladze,
Susanne Dreisigacker, Roberto-Javier Peña &
Masahiro Kishii
Global Wheat Program - CIMMYT

2. Stem Rust on Durum Wheat
Specificity of the pathogen and current presence
„ Ug99+variants
■ Present in Kenya, Ethiopia, Yemen, Iran
■ Widespread resistance in most durum
germplasm groups
„ Ethiopian races, pre-dating Ug99
■ Not as well characterized
■ Sr13+Sr9e combined virulence (Olivera et al. 2010)
■ Very little resistance (5%) in all germplasm groups
worldwide (Olivera et al. 2010)
■ Confined to Ethiopia?, Sr13 virulence present in Turkey

3. Stem Rust on Durum Wheat
Durum areas threatened by the “Ethiopian” races:
„ Durum areas of Central India (1.0-1.5 million ha)
■ Through Yemen, most likely path as confirmed by migration of Ug99
■ Stem rust (less virulent races) already endemic in the region
„ Turkey, North-Africa, Middle-East
(>5 million ha)
■ Less likely dissemination path, but cannot
be ignored
■ Sr13-virulence present in Turkey
■ Durum critical in these areas
■ Historically favorable climatic conditions for
the development of stem rust epidemicsDavid Hodson et al. 2008
„ Threat likely to increase with warming temperatures earlier in the
cropping seasons as predicted by climate change scenarios

4. Breeding for Stem Rust Resistance in Durum Wheat
Screening in Njoro-Kenya vs. Debre Zeit-Ethiopia
y = 0.9729x + 22.67
R2
= 0.223
0
10
20
30
40
50
60
70
80
-5 0 5 10 15 20 25 30 35 40 45
SR reading KENYA
SRreadingETHIOPIA

5. Breeding for Stem Rust Resistance in Durum Wheat
The basis of our strategy
„ Establishment of bi-annual screening program in Ethiopian “hot-spot”
■ Hosted by the Debre Zeit Ag. Res. Center
■ Artificial inoculation with mixture of relevant races (Ethiopian races + Ug99)
■ Screening of 1000s of lines annually:
• Resistance sources discovery for crossing
• Resistance confirmation in new advanced lines
• Genetic studies for resistance characterization
Photos: Dr. Ayele Badebo

6. Breeding for Stem Rust Resistance in Durum Wheat
Rare resistance to start with in 2009… but enough to work with
50 – 70 S
80 – 100s
278
64
71.3
16.4
Reaction
Class
Number of
Lines
Percent of
Total
10 MR – 20 MRMS 12 3.1
30 MR – 40 MSS 36 9.3
Data from Debre Zeit, off-season 2009
390 Elite Lines

7. Breeding for Stem Rust Resistance in Durum Wheat
Emphasis in CIMMYT crossing program
296
456
268 219
0
200
400
600
800
1000
1200
2009 2010 2011 2012
NumberofCrosses
Year
Crosses made for Stem Rust Resistance 2009 - 2012
Stem Rust Crosses
20 – 46% of program’s crossing effort
„ Resistance Sources
■ CIMMYT Elite
■ European germplasm
■ North-American
germplasm
■ ICARDA germplasm
■ Genetic resources
■ Stocks with marked
genes (MAS)

8. Breeding for Stem Rust Resistance in Durum Wheat
Selection stream: parallel selection Ethiopia/Mexico of new fixed lines
F3
Toluca
F2
Obregon
F6
PYT Obregon
F5
Toluca/Batan
F4
Obregon
F6
Off season
Debre Zeit
F7
HR Batan
F7
Main season
Debre Zeit
F8
Rep YT Obregon
F8
Off season
Debre Zeit
Distribution
Globally
Release
Ethiopia
Selection for LR, YR, agronomic type, earliness and grain-fill
MEXICO: Selection for yield, drought tolerance, quality
ETHIOPIA: Selection for Stem Rust resistance

9. Breeding for Stem Rust Resistance in Durum Wheat
Significant increase in resistant germplasm distributed globally
Number % Number % Number % Number %
Reaction Group of Lines Total of Lines Total of Lines Total of Lines Total
Resistant 20 13.2 5 3.3 17 10.7 26 12.0
Moderately Resistant 5 3.3 17 11.3 44 27.7 60 27.8
Useful for Stem Rust 25 16.4 22 14.6 61 38.4 86 39.8
Moderately Susceptible 12 7.9 19 12.7 5 3.1 2 0.9
Susceptible 115 75.7 109 72.7 93 58.5 128 59.3
N = 152 N = 150 N = 159 N = 216
43 IDYN+IDSN 44 IDYN+IDSN 45 IDYN+IDSN 46 IDYN+IDSN
Distributed 2011 Distributed 2012 Distributed 2013 Distributed 20142009: 3.1%

10. Breeding for Stem Rust Resistance in Durum Wheat
Significant increase in resistant germplasm distributed globally while
maintaining agronomic performance
0
20
40
60
80
100
120
140
85 90 95 100 105 110 115 120 125 130 135
Numberoflinesinclass
Grain Yield as % of Check JUPARE C2001
Yield Distribution under FULL IRRIGATION within germplasm distributed in
2013 and 2014 International Nurseries
ALL (N=304)
Stem Rust R/MR (N=124)
0
20
40
60
80
100
120
85 90 95 100 105 110 115 120 125 130 135
Numberoflinesinclass
Grain Yield as % of Check JUPARE C2001
Yield Distribution under DROUGHT within germplasm distributed in 2013
and 2014 International Nurseries
ALL (N=291)
Stem Rust R/MR (N=115)
„ Stem Rust Resistant lines have similar distribution than other lines
■ Yield Potential
■ Drought Tolerance
■ Quality attributes (gluten strength & yellow color)

11. Breeding for Stem Rust Resistance in Durum Wheat
Stacking alien genes of resistance via MAS
Sr25/Lr19 7AL L. ponticum Durum w heat 1
PsyA1+PsyER4 Co-dominant
Full phenotypic expression, routine use
in parent characterization and MAS
cfa2123 Co-dominant
csKP81 Co-dominant
Inheritance
Phenotypic Validation and use in
program
Sr22
Full phenotypic expression, routine use
in parent characterization and MAS
Location Origin
Source
Originally
Used
7AL T. boeticum Bread w heat
Gene
Marker
Designation
1: Transferred to durum by Dr. Adam Lukashewski, U.C. Riverside
Sr22
(cfa2123, cfa2019)
Sr25
(PSY1-EF2_ER4)
Photos: Susanne Dreisigacker

12. Breeding for Stem Rust Resistance in Durum Wheat
Sr22 and Sr25 loci tightly linked , essentially inherited together, attempt at
better gene stewardship…
Xgpw2242-8.2
Xfba2430.0
Xfba17 Xgpw413013.0
Xcfd6218.7
Xfba23122.4
XEF1R33.9
Xfba12738.9
Xfba10958.4
Xbcd143859.4
Xgpw320165.3
Xgpw323476.2
Xfbb22286.8
Xcfa205697.8
Xfbb7998.9
Xfba7199.5
Xfbb366106.8
Xgpw3208125.4
Xcfd6129.5
Xgpw7313136.1
Xpsr165136.6
Xwmc182137.7
Xpsp3050138.4
Xcfa2110147.5
XksuA5168.5
Xbc9O10169.6
Xglk478174.5
XksuG12178.2
Xcfa2123193.3
Xfba69198.7
Xpsp3094 Xgpw2252210.6
Xtam51219.9
Xcfa2019224.0
Xcfa2293232.4
XksuD2232.8
Xfba350244.7
Xwg232.1253.6
Xwg232.2253.8
Xcfa2040256.2
XksuH9267.5
7AL-1-0.39-0.717AL-18-0.9-1
Sr22
(cfa2123, cfa2019)
Sr25
(PSY1-EF2_ER4)
Chr. 7A
(Courtot x C.S.)
DWSr22 x Elite 1
F1Sr22
DWSr25 x Elite 2
F1Sr25X
Double-Cross
Population
F2
F6
F8
Testing SR
Testing SR
Yield, Drought
Quality
MAS

13. Breeding for Stem Rust Resistance in Durum Wheat
Advanced lines with linked Sr22+Sr25
„ GISH of L. Ponticum segment
■ Telomeric
„ GISH of T. Boeticum segment
■ Not yet available
Photos: Masahiro Kishii

14. Breeding for Stem Rust Resistance in Durum Wheat
Advanced lines with linked Sr22+Sr25: Characteristics
„ Confirmed homozygocity for both genes
■ Markers stably homozygous in F6 – F8 head-rows
■ Stably resistant over 2-3 seasons at Debre Zeit
„ Improved quality parameters
■ Better gluten strength than most local cultivars
■ Significantly higher yellow color than local cultivars
„ Variable yield performance and drought tolerance
■ Obregon: some yield penalty due to lower kernel size
■ Ethiopia: under evaluation
■ Second round breeding started!!

15. CIMMYT – DZARC Joint Breeding Effort for Stem Rust
Resistance in Durum Wheat: Conclusions
„ Strategy of parallel Selection Mexico/Ethiopia
has been successful
■ Significant progress in frequency of SR
resistant or moderately resistant lines in
CIMMYT outgoing germplasm
■ Useful variability for yield potential, drought
tolerance and quality maintained in new
resistant germplasm
„ Debre Zeit phenotyping platform has been key!
■ Testing facilities have been enhanced, effort
needs sustaining
„ MAS with gene stewardship in mind provided
valuable germplasm
■ If not usable for cultivar release, provides useful
parental stocks for further breeding

16. Stem Rust Resistance in Durum Wheat
Research efforts to provide information and markers for breeding
„ Association Mapping of Stem Rusts resistance
■ Beachell-Borlaug scholar Tesfaye Dugo Letta
■ Led y Prof. Tuberosa team, Univ. Bologna, Italy
■ Results from adult plant reaction and seedling published
(Letta et al., TAG, 2013; Letta et al., Plant Genome, 2014)
„ Mapping of Stem Rust Resistance from Boohai
■ Beachell-Borlaug scholar Tesfaye Dugo Letta
■ Led y Prof. Tuberosa team, Univ. Bologna, Italy
■ Phenotyping done, mapping in process
„ Mapping of Stem Rust Resistance from COCORIT
■ Collaboration with Dr. Curtis Pozniak, Univ. Saskatchewan
■ Preliminary results presented, manuscript in progress