Greg Edmeades1, Jill Cairns2, Jeff Schussler3,

Amsal Tarakegne2, Stephen Mugo2,

Dan Makumbi2 and Luis Narro2

1 Consultant; 2 CIMMYT; 3 Pioneer Hi-Bred International

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

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

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

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

5

-- Maize areas will be hotter and drier, dimmer, and

subject to extreme weather

-- Opportunities in winter and in cool northern areas

If we do nothing and temperature

rises in a droughted crop…

6

Source: D. Lobell et al., 2011

Variable field environments Source: Kitchen et al., 1999

7

Measured yields ranged from 1 to 10 t/ha

Meanwhile, in temperate zones, plant

density has steadily risen

1986 1988 1990 1992 1994 1996 1998 2000 20025.0

5.5

6.0

6.5

7.0

Slope = 689 plants ha-1 yr-1

R2 =0.98**; 16 df

Source : Annual Corn Belt Farm Survey data

Year of farmer survey

Seed

s p

lan

ted

m-2

1920 1940 1960 1980 2000

5

10

15

20

Slope = 760 plants ha-1 yr-1

N=50; R2=0.35; P<.001

Year of release

Op

tim

um

den

sit

y

(pla

nts

m-2

)

Density tolerance = general tolerance to abiotic stresses 8

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

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

10

Tremendous increase in

interest in drought tolerance in maize in the last 40 years

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

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

Gains were maintained outside of

adaptation zone

2 4 6 80

2

4

6

8

La Posta Seq C6

La Posta Seq C0

Mean environment yield (t ha-1)

Va

rie

ty y

ield

(t

ha

-1)

14

Africa: experimental hybrids (4) vs. best private

company hybrids (checks)

23 randomly stressed locations, Eastern and southern Africa

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

0.0 2.0 4.0 6.0 8.0 10.0

Y ie ld o f the tr ia l (t/ha )

Yie

ld o

f th

r v

ari

ety

(t/

ha

)

Experimental Checks

Source: Banziger et al., 2006 15

Gains in yield in US hybrids Source: Schussler et al. 2011

16

Year of Hybrid Release

1930 1940 1950 1960 1970 1980 1990 2000 2010

Gra

in Y

ield

(t/

ha

)

2

4

6

8

10

12

14

16

18

y = 3.549 + 0.072x (r2 = 0.90): Drought

y = 8.269 + 0.092x (r2 = 0.85): Irrigated

y = 4.966 + 0.089x (r2 = 0.96): TPE

Irrigated, CA

Drought, CA

Target rainfed

environment

Flowering still a vulnerable growth stage GY vs. ASI in elite Corn Belt hybrids

126 elite hybrids, 2 water regimes, 2002

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

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

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

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

Response of grain yield to recurrent

selection under low and high N (Source: Lafitte and Bänziger 1997, DDLTM: 485-489)

Low N High N0.0

2.5

5.0

7.5C0

C5

Gain 5.1%/cyc84 kg/ha/cycle*

Gain 2.4%/cyc120 kg/ha/cycle*

Evaluation environment

Gra

in y

ield

(to

n h

a-1

)

23

Effect of design and index selection on

predicted gains under low N

(Source: Bänziger and Lafitte (1997), DDLTM: 401-404)

RCBD Lattice Lat + index0.0

0.1

0.2

0.3RCBD

Lattice

Lat + index100%116%

137%

Options

Pre

dic

ted

sele

cti

on

resp

on

se (

t h

a-1

)

24

Leveraging other traits…. Proportion of gains in drought tolerance

captured under low N

0.3 0.4 0.5 0.6 0.7 0.80.2

0.4

0.6

0.8

1.0

Low High

N Stress level (1-GYloN/GYhiN)

Pro

po

rtio

n o

f D

RT

gain

scap

ture

d

25

Temperate maize in Iowa NUE has increased with yield potential

26 Source: USDA, 2009

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

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

Aluminum damage

Susceptible

Tolerant

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

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

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

Soil electrical conductivity maps help

avoid some field variability Source: J. Cairns

Chiredzi, Zimbabwe

33

Africa: genetic correlations between target

environments and managed stresses

34

Selection

environment

Genetic correlation

Optimal 0.80

Managed drought 0.64

Low N 0.91

Target = random abiotic stress with yields < 3 t/ha

Southern Africa, 2001-9 (Weber et al. 2011)

Africa: breeding approaches: conventional

35

Preliminary gains: Stage 2 early topcross trials vs. SC403

Southern Africa (N=88) Source: A. Tarekegne

Looking forward: sources

Donors are being identified

CLWN 201 for low N tolerance (G Atlin, IMAS)

For heat and drought tolerance (J. Cairns, DTMA)

36

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

Remote sensing:

The normalized difference vegetation index (NDVI)

Infrared thermometry and spectral reflectometer

NIRS

New secondary traits under evaluation

37

BIOMASS / NDVI

y = 79,802x - 8,6683

R2 = 0,8845

0,00

10,00

20,00

30,00

40,00

50,00

60,00

0,000 0,100 0,200 0,300 0,400 0,500 0,600 0,700 0,800 0,900

NDVI

SH

OO

T (

gr.

DW

)

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

Genome-wide predictions vs. field

performance in temperate germplasm Source: Schussler et al., 2011

39

Observed vs. predicted relative grain yield of hybrids under

severe flowering stress in Woodland, CA

r = 0.94***

Yield BLUPs for eight conventional

drought tolerant hybrids Source: Schussler et al., 2011

40

Drought

stress

No drought

stress

Optimum® AQUAmaxTM

(t/ha)

6.89 11.94

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

Transgenics

41

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

Critical factors for impact

42

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

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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