Perspectives on Applied Aspects of Breeding for Rust Resistance

Perspectives on Applied Aspects of Breeding for Rust Resistance

2013 BGRI Technical Workshop New Delhi, India

Moderator: Ravi P. Singh

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)

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)

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

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

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)

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

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/

Sr55!

8.5 10.4

wPt7200 wPt7750 wPt8460 wmc175

82.0 92.8 100.7 118.8

wPt2565 csLV34 wPt2689

wPt1029

51.0 58.5

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

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

Num

ber o

f ent

ries

(%)

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%

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

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

Gra

in Y

ield

(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%