Presentacion de 11th Asian Maize Conference which took place in Beijing, China from November 7 – 11, 2011.

1. Greg Edmeades1, Jill Cairns2, Jeff Schussler3,
Amsal Tarakegne2, Stephen Mugo2,
Dan Makumbi2 and Luis Narro2
1 Consultant; 2 CIMMYT; 3 Pioneer Hi-Bred International

2. Acknowledgments
 Project staff of WEMA, DTMA and IMAS
 NARS in sub-Saharan Africa and the Andean zone
 Colleagues from Pioneer Hi-Bred Int.
 CIMMYT
 Dedicated Post Docs, and field staff
 Colleagues
2

3. What we’ll cover today
 Introduction
 Lessons from the past
 Drought, Low N, acid soils
 Guiding principles
 Looking forward
 Breeding approaches
 Key components : agronomy, partnerships
 Conclusions
3

4. Introduction
 Population growth: 7 bn today, 9.1 bn by 2050
 Limits on arable land area expansion
 Maize in more marginal environments
 Increase of staple crop yield is slowing
 Climate change
BUT we have:
•New tools
•Better genetic and physiological information
4

5. Environment is changing
 Temperature: +1-1.5C by 2030; +2.5-3oC by 2050
 Water: Rainfall, runoff increase; crops are drier
 Probable increase in climatic extremes
 Global dimming in Asia
 N prices rise; soil acidification from N application
-- Maize areas will be hotter and drier, dimmer, and
subject to extreme weather
-- Opportunities in winter and in cool northern areas
5

6. If we do nothing and temperature
rises in a droughted crop…
Source: D. Lobell et al., 2011
6

7. Variable field environments
Source: Kitchen et al., 1999
Measured yields ranged from 1 to 10 t/ha
7

8. Meanwhile, in temperate zones, plant
density has steadily risen
7.0
Slope = 689 plants ha-1 yr-1 Slope = 760 plants ha-1 yr-1
Seeds planted m-2
20 N=50; R2=0.35; P<.001
Optimum density
6.5
R2 =0.98**; 16 df
(plants m -2)
15
6.0
10
5.5
Source: Annual Corn Belt Farm Survey data 5
5.0
1986 1988 1990 1992 1994 1996 1998 2000 2002 1920 1940 1960 1980 2000
Year of farmer survey Year of release
Density tolerance = general tolerance to abiotic stresses
8

9. But why not select just for yield?
Secondary traits and selection
 Useful secondary traits (under stress) are
 Correlated with yield under stress
 High and stable heritability
 Cheap, fast to measure
 When used with yield in a selection index, heritability
of index rises
 Index increased genetic gain by 14% under low N
(Bänziger and Lafitte, 1997)
9

10. Lessons from the past: drought
 Tropical: research started by CIMMYT in 1975
on a single population
 Extended to 7 populations in 1985
 Exported to Africa in 1996 and to Asia in 2000
 Temperate: research began in mid 1960s led by
Pioneer and DeKalb
 Amplified from 1997 onwards by all major companies
Tremendous increase in
interest in drought tolerance in maize in the last 40 years
10

11. Selection in tropical populations
 Recurrent S1 or FS selection; 10% intensity, rain-free
locations; 4 to 9 cycles; 6 populations
 Heat and drought in Obregon, drought in Tlaltizapan
 Three managed drought stress regimes: WW, IS and
SS; 2 reps
 Primary trait: Grain yield under stress, optimal
 Secondary traits: ASI, EPP, staygreen, leaf rolling,
tassel size
 1988: DTP started from DT sources – improved,
temperate, tropical, landraces, mixed color, open-ended
11

12. Gains per cycle under stress (drought;
low N) or unstressed environments.
N (popn)= 6; N (cycles)=2-9; N (env.) = 4-10
Grain yield ASI
kg ha-1 cycle-1 d cyc-1
Population Drought Unstressed Low N Drought
Maximum 288** 177** 233** -2.1**
Minimum 80** 38** 64 ns -0.3**
Mean 166 99 166 -1.0
Relative yield (%) 30 100 59 30
Source: Edmeades, 2006
12

14. Gains were maintained outside of
adaptation zone
8
Variety yield (t ha-1)
La Posta Seq C6
6
4
2 La Posta Seq C0
0
2 4 6 8
Mean environment yield (t ha -1)
14

15. Africa: experimental hybrids (4) vs. best private
company hybrids (checks)
23 randomly stressed locations, Eastern and southern Africa
14.0
12.0
Yield of thr variety (t/ha)
10.0
8.0
6.0
4.0
2.0
0.0
0.0 2.0 4.0 6.0 8.0 10.0
Y ie ld o f th e tr ia l (t/h a )
E xperim ental C hecks
Source: Banziger et al., 2006 15

16. Gains in yield in US hybrids
Source: Schussler et al. 2011
18
y = 3.549 + 0.072x (r2 = 0.90): Drought
16 y = 8.269 + 0.092x (r2 = 0.85): Irrigated Irrigated, CA
y = 4.966 + 0.089x (r2 = 0.96): TPE
14
Target rainfed
Grain Yield (t/ha)
12 environment
10
Drought, CA
8
6
4
2
1930 1940 1950 1960 1970 1980 1990 2000 2010
Year of Hybrid Release
16

17. Flowering still a vulnerable growth stage
GY vs. ASI in elite Corn Belt hybrids
126 elite hybrids, 2 water regimes, 2002

18. What we learned about drought
tolerance…..
 Gains: 100 kg/ha/yr in tropicals using MSEs and
70 kg/ha/yr in temperates using METs
 Pioneer: 1 MSE site = 10 MET sites in the target area
 Drought tolerance is at no cost to yield potential
 Useful secondary traits: barrenness and ASI
 Susceptibility at flowering is reduced by
conventional selection using wide area testing
 Temperate hybrids lack variation for functional
staygreen under stress
 **Guard against escapes: monitor flowering date
18

19. Heat tolerance
Possible sources of drought and heat tolerance
Source: DTMA Association Mapping Panel (J. Cairns)
Drought tolerance does not automatically equate to heat tolerance
19

20. Lessons from the past: nitrogen
 NUE research started in
temperate germplasm in
the 70s and 80s
 Low N tolerance started
in CIMMYT in 1986
 N depletion
 Recurrent selection
20

21. Selection in tropical populations
 Across 8328 BN: Recurrent FS selection; depleted low
N plot beside high N plot (200 kg N/ha) in Poza Rica
 Primary trait: Grain yield under stress, optimal
 Secondary traits: ASI, EPP, staygreen; monitor
anthesis
 Pool 16 BNSEQ: S1’s evaluated under low N and
drought
21

22. 22

23. Response of grain yield to recurrent
selection under low and high N
(Source: Lafitte and Bänziger 1997, DDLTM: 485-489)
7.5
C0
Grain yield (ton ha -1)
Gain 2.4%/cyc
120 kg/ha/cycle* C5
5.0
Gain 5.1%/cyc
2.5 84 kg/ha/cycle*
0.0
Low N High N
Evaluation environment
23

24. Effect of design and index selection on
predicted gains under low N
(Source: Bänziger and Lafitte (1997), DDLTM: 401-404)
0.3
137% RCBD
Predicted selection
response (t ha-1)
116% Lattice
0.2
100% Lat + index
0.1
0.0
RCBD Lattice Lat + index
Options
24

25. Leveraging other traits….
Proportion of gains in drought tolerance
captured under low N
Proportion of DRT gains
1.0
captured
0.8
0.6
0.4
Low High
0.2
0.3 0.4 0.5 0.6 0.7 0.8
N Stress level (1-GYloN/GYhiN)
25

26. Temperate maize in Iowa
NUE has increased with yield potential
26
Source: USDA, 2009

27. Summary from past low N research
 Gains of around 5% per year under low N possible in
“improved” germplasm at yields of 2 ton/ha
 Key traits are GY, staygreen, kernels per ear, ASI
 Strong correlation with drought tolerance under
moderate N stress
 Soil uniformity and designs strongly affect gain
27

28. Lessons from the past: soil acidity
 Acid soils (pH < 5.5) affect 3,950 M ha globally
 As pH falls Al3+ ions damage roots; P less available
 Screening: normal vs. 40-60% Al3+ saturation and
two levels of P (4 and 15 ppm)
 Program commenced in the 1970s in Cali Colombia;
based on EMBRAPA research
 Callose formation in roots related to injury from Al3+
28

29. Aluminum damage
Susceptible
Tolerant

30. Maize grain yield on acid soils
CIMMYT 1975-2008

Narro, 2011
1975 1994 2000 2008
Under typical soil conditions: pH 4.7; Al3+ saturation = 60%
There has been remarkable progress

31. Principles emerging
 Most maize populations have a low frequency of
stress adaptive alleles, often with small effects
 Increased stress tolerance possible at no cost to
yield potential
 Well-targeted managed stress environments
efficiently accelerate gains for stress tolerance
 Secondary traits point to key mechanisms--- but
contribution will dissipate with selection
31

32. Looking forward….
Phenotyping is way behind genotyping in cost per dp
Basics that matter
 Uniform fields and uniform plant spacing, input application
 The right experimental design and spatial analysis
 Represents TPE in photoperiod and temperature
 Plot management: Grouping by maturity and/or vigor level;
adequate borders
 Measure only traits that improve repeatability
32

33. Soil electrical conductivity maps help
avoid some field variability
Source: J. Cairns
Chiredzi, Zimbabwe
33

34. Africa: genetic correlations between target
environments and managed stresses
Target = random abiotic stress with yields < 3 t/ha
Southern Africa, 2001-9
(Weber et al. 2011)
Selection Genetic correlation
environment
Optimal 0.80
Managed drought 0.64
Low N 0.91
34

35. Africa: breeding approaches: conventional
Preliminary gains: Stage 2 early topcross trials vs. SC403
Southern Africa (N=88) Source: A. Tarekegne
35

36. Looking forward: sources
Donors are being identified
 CLWN 201 for low N tolerance (G Atlin, IMAS)
 For heat and drought tolerance (J. Cairns, DTMA)
DTMA Pedigree GY (t ha-1)
91 CML311/MBR C3 Bc F12-2-2-2/CML312SR 0.63
238 DTPYC9-F46-1-2-1-2 / CML312SR 0.59
. La Posta Seq C7-F64-2-6-2-2/CML312SR 0.55
62 CLA44 /CML312SR 0.49
231 DTPYC9-F143-5-4-1-2/CML-312SR 0.46
44 CML412/CML312SR 0.19
Trial mean 0.24 36

37. New secondary traits under evaluation
 Remote sensing:
 The normalized difference vegetation index (NDVI)
 Infrared thermometry and spectral reflectometer
 NIRS
BIOMASS / NDVI
60,00
50,00 y = 79,802x - 8,6683
2
R = 0,8845
40,00
SHOOT ( gr. DW)
30,00
20,00
10,00
0,00
0,000 0,100 0,200 0,300 0,400 0,500 0,600 0,700 0,800 0,900
NDVI 37

38. Looking forward: genome wide
selection
 Conventional + GWS: careful phenotyping and
genotyping by sequencing with 10-450K SNPs
 GEBVs as accurate as phenotypic evaluation in a
single drought trial (with H = 0.2-0.4);
 Calculated from several traits
 Cull DH lines before crossing and testing (Semagn et
al. 2011)
38

39. Genome-wide predictions vs. field
performance in temperate germplasm
Source: Schussler et al., 2011
r = 0.94***
Observed vs. predicted relative grain yield of hybrids under
severe flowering stress in Woodland, CA 39

40. Yield BLUPs for eight conventional
drought tolerant hybrids
Source: Schussler et al., 2011
Drought No drought
stress stress
Optimum® AQUAmaxTM 6.89 11.94
(t/ha)
Leading checks (t/ha) 6.56 11.59
Difference (t/ha) 0.33 0.35
N 223 >1200
Improvement (%) 5.0 3.0
Sites in high plains of the US (NE, KS, CO, MO, TX) 2008-10
40

41. Transgenics
 Drought: MON 87460
 Commercial launch in the US in 2012
 WEMA: Deploying MON87460 in sub-Saharan Africa
stacked with Bt --- 2018
 Additive effect assumed
 Low N:
 Pioneer: actively screening genes and constructs
 Commercial: US in 2017?
 Royalty free in sub-Saharan Africa in 2020 ? with IMAS
41

42. Critical factors for impact
 Agronomy
 Yield potential, input use efficiency
 Conservation tillage
 Hybrid x management interactions increasingly important
 Dissemination
 Affordable seed for risky environments – private and public
 Partnerships
 Public-Private: hybrids; IP protection, GM technologies
 Policies to encourage private investment
42

43. Conclusions….
We could > double impact in stressed environments
when
 Tools are integrated: Genome-wide selection,
conventional selection, DH production, well-run METs
 Proven sources of stress tolerance (including
transgenes) are widely used
 Stresses in MSEs are matched to the target environment
 Repeatability of field trials such that Sd ≤ 0.2 t/ha
 Agronomic practices exploit improved genetics
 Seed systems, markets, & infrastructure function well
 Partnerships: private-public
We have the tools. The game is ours to lose 43

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