Ravi Singh

1. Perspectives on Applied Aspects of
Breeding for Rust Resistance
2013 BGRI Technical Workshop
New Delhi, India
Moderator: Ravi P. Singh

2. Panelists:
• Vinod Prabhu, Indian Agricultural Research Institute (India)
• Goodarz Najafian, Seed and Plant Improvement Institute (Iran)
• Peter Njau, Kenya Agricultural Research Institute (Kenya)
• Francois Koekemoer, Sensako (South Africa)
• Jim Anderson, University of Minnesota (USA)
• Yuchun Zou, Sichuan Academy of Agricultural Sciences (China)

3. A successful variety is the sum of various traits-
integrating simultaneous improvement for multiple
traits is the only way forward
Core traits (ideally should be
present in all CIMMYT wheats)
„ High and stable yield potential
„ Durable resistance to Rusts-
Stem (Ug99), Stripe and Leaf
„ Water use efficiency/ Drought
tolerance
„ Heat tolerance
„ Appropriate end-use quality
Additional traits for specific mega-
environments
„ Durable resistance to diseases and pests
® Septoria leaf blight (ME2)
® Spot Blotch (ME5)
® Tan Spot (ME4)
® Fusarium – head scab and myco-toxins
(ME2/4/5)
® Karnal bunt (ME1)
® Root rots and nematodes (ME2)
„ Enhanced Zn and Fe concentration
(ME1/5)

4. Challenges to wheat breeding
● Under resourced programs- financially and human-
(some other crops more remunerative than wheat)
● High expectations for making fast progress with complex
traits such as grain yield, stress tolerance, end-use
quality, durable disease resistance
● Inadequate phenotyping facilities to detect smaller
differences (often high CVs in trials, disease nurseries)
● Poor training in universities for field based research
Stronger collaboration and
partnerships essential

5. Breeding for rust resistance
● Longer-term objective versus short-term emergency response to
handle situations such as Ug99, aggressive yellow rust race
● Only few investing on the search for new resistance genes but
many programs worldwide depend on this-- potentially leading to
limited genetic diversity at a given time
● Many publications on linked markers for resistance genes but only
few useful when tried by breeding programs-- cost and logistics
remains a major issue
● Understanding the genetic basis of resistance in varieties is often
post analysis-- a reality unlikely to change unless diagnostic
markers for effective resistance genes are developed

6. Race-specific resistance to stem rust on 6DS
• Race-specific gene for Ug99 resistance mapped on 6DS in several
CIMMYT/US wheats
• Similar effects as SrTmp or SrCad
• Close to Sr42
• Resistance enhanced with other APR genes
Lopez-Vera et al. 2013 (manuscript under review)

7. Utilizing and deploying resistance more
responsibly- gene stewardship
● Evergreen debate however unlikely to happen unless
§ ?
§ ?
● Importance of larger genetic diversity for resistance genes versus
few genes used more responsibly
● Using race-specific vs. quantitative adult plant resistance
● Role of multi-pathogen resistance genes such as ABC transporter
Lr34/Yr18/Sr57/Pm38/Sb1/Bdv1 in conferring resistance durability
● Scientists of various disciplines working together
Resistance breeding need to remain simple for
adoption by large number of breeding programs

8. Building complex adult plant resistance to stem rust for durability
Diversity for slow rusting, minor Sr genes: 13 genomic regions identified in
CIMMYT wheat through bi-parental and association mapping studies
1A 1B 2B 3B 3D 4A 4D 5B 6B 7B 7D
wPt0128
wPt4987
wPt1560
wPt1328
Lr46
Yr29
Sr58
Pm39
wmc154
wPt9668
41.4
53.4
csSr2
gwm533
Barc133
wPt2921
GBS76
gwm604
wPt1304
GBS558
14.0
15.3
20.3
21.75
gwm371
csLV46
wPt6997
wPt5749
wPt4487
68.1
77.2
87.8
gwm165
gwm192
Lr67
Yr46
Sr55
Pm46
wPt3774
wPt1922
Cfd13
wPt5333
wPt5037
0.0
3.7
29.7
31.5
45.4
csNLRR
gwm146 Lr68
wPt5343
wPt7351
Lr34
Yr18
Pm38
Sr57
126.1
126.8
Sr2
Yr30
Lr27
Pm
Four genes with pleiotropic genetic effects on multiple diseases now known:!
Sr2/Yr30/Lr27/Pm, Lr34/Yr18/Pm38/Sr57, Lr46/Yr29/Sr58/Pm39, Lr67/Yr46/Pm46/
8.5
10.4
wPt7200
wPt7750
wPt8460
wmc175
82.0
92.8
100.7
118.8
wPt2565
csLV34wPt2689
wPt1029
51.0
58.5

9. Integrating resistance to Ug99 race of stem rust fungus in CIMMYT wheats
Mexico (Cd. Obregon-Toluca/El Batan)- Kenya International Shuttle Breeding:
a five-year breeding cycle)
Cd. Obregón 39 masl
High yield (irrigated), Water-use efficiency,
Heat tolerance, Leaf rust, stem rust (not Ug99)
Toluca 2640 masl
Yellow rust
Septoria tritici
Fusarium
El Batán 2249 masl
Leaf rust, Fusarium
Njoro, Kenya 2185 masl
Stem rust (Ug99 group)
Yellow rust
● Targeted crosses for shuttle breeding made in 2006 and 1st group of
populations planted in Kenya in 2008
● 2000 F3/F4 populations undergo Mexico-Kenya shuttle
● High yielding, resistant lines derived from 1st group of Mexico-
Kenya shuttle distributed worldwide in 2011, 2012 and 2013

10. Progress in grain-yield potential of new bread wheat lines developed since the launch of Borlaug Global
Rust Initiative (1st year yield data from: Ciudad Obregon, Mexico 2005, 2010 and 2013)
Several fold increases in new breeding lines derived from crosses made
progressively over years with higher yields than the checks
0
5
10
15
20
25
<60 60-64 65-69 70-74 75-79 80-84 85-89 90-94 95-99 100-104 105-109 110-114 >115
Numberofentries(%)
Grain yield (% Tacupecto 2001 or Roelfs 2007)
0.1% (4 entries)
2.1% (104 entries)
4.5% (426 entries)
2005
n=4814
mean 80%
2010
n=4956
mean 90%
2013
n=9436
mean 94%

11. Ug99 stem rust resistance in 604 wheat entries included in various
international trials for distribution in 2013/2014
(
46% entries possess high to adequate adult-plant resistance &
another 46% carry diverse race-specific resistance genes often
in combination with Sr2 and other minor APR genes
Adult plant resistance Stem rust Entries Race-specific Entries
category severity (%) No. % genes No. %
Near-Immune Resistant 1 19 3 Sr13 27 4
Resistant 5-10 52 9 Sr22 7 1
Resistant- Mod. Res. 15-20 133 22 Sr25 54 9
Moderately Resistant 30 71 12 Sr26 5 1
Sr1A.1R 9 1
Mod. Res.- Mod. Sus. 40 29 5 Sr42: 6DS gene 88 15
Mod. Sus.- Susceptible 50-100 12 2 SrHuw234 7 1
SrND643 74 12
Sr? 12 2

12. Increased yield potential of new wheat varieties contributes to
enhance productivity in farmers’ fields and fast adoption
Yield increase Yield increase R2
Time period per year (%) per year (kg/ha) Year vs Yield
1951-2012 2.15 78 0.882
1951-1960 4.98 88 0.664
1961-1970 3.51 113 0.410
1971-1980 1.69 72 0.220
1981-1990 1.08 54 0.207
1991-2000 1.59 84 0.449
2001-2010 1.15 62 0.567
2001-2013 1.63 114 0.553
Average wheat grain yield trends in farmers fields in Yaqui Valley, Mexico from
1951-2013 despite a reduction in number of irrigations from six to four
Source: K. Sayre
0
1000
2000
3000
4000
5000
6000
7000
8000
1950 1960 1970 1980 1990 2000 2010
GrainYield(kg/ha)
Year of Harvest
Yield = -1.52 x 10 to the fifth + 78.7 kg/ha/year
r2 = 0.887
Yield Increase/year = 2.13%