Greg Edmeades1, Jill Cairns2, Jeff Schussler3,        Amsal Tarakegne2, Stephen Mugo2,          Dan Makumbi2 and Luis Narr...
Acknowledgments Project staff of WEMA, DTMA and IMAS NARS in sub-Saharan Africa and the Andean zone Colleagues from Pio...
What we’ll cover today Introduction Lessons from the past    Drought, Low N, acid soils Guiding principles Looking fo...
Introduction Population growth: 7 bn today, 9.1 bn by 2050 Limits on arable land area expansion   Maize in more margina...
Environment is changing  Temperature: +1-1.5C by 2030; +2.5-3oC by 2050  Water: Rainfall, runoff increase; crops are dri...
If we do nothing and temperature    rises in a droughted crop…          Source: D. Lobell et al., 2011                    ...
Variable field environments        Source: Kitchen et al., 1999Measured yields ranged from 1 to 10 t/ha                   ...
Meanwhile, in temperate zones, plant                  density has steadily risen                    7.0                   ...
But why not select just for yield?          Secondary traits and selection Useful secondary traits (under stress) are   ...
Lessons from the past: drought Tropical: research started by CIMMYT in 1975  on a single population   Extended to 7 popu...
Selection in tropical populations Recurrent S1 or FS selection; 10% intensity, rain-free    locations; 4 to 9 cycles; 6 p...
Gains per cycle under stress (drought;   low N) or unstressed environments.           N (popn)= 6; N (cycles)=2-9; N (env....
Gains were maintained outside of        adaptation zone                              8     Variety yield (t ha-1)         ...
Africa: experimental hybrids (4) vs. best private          company hybrids (checks)   23 randomly stressed locations, East...
Gains in yield in US hybrids                                              Source: Schussler et al. 2011                   ...
Flowering still a vulnerable growth stage      GY vs. ASI in elite Corn Belt hybrids            126 elite hybrids, 2 water...
What we learned about drought           tolerance….. Gains: 100 kg/ha/yr in tropicals using MSEs and  70 kg/ha/yr in temp...
Heat tolerancePossible sources of drought and heat tolerance            Source: DTMA Association Mapping Panel (J. Cairns)...
Lessons from the past: nitrogen NUE research started in  temperate germplasm in  the 70s and 80s Low N tolerance started...
Selection in tropical populations Across 8328 BN: Recurrent FS selection; depleted low  N plot beside high N plot (200 kg...
22
Response of grain yield to recurrent                            selection under low and high N                            ...
Effect of design and index selection on     predicted gains under low N                      (Source: Bänziger and Lafitte...
Leveraging other traits….Proportion of gains in drought tolerance         captured under low N   Proportion of DRT gains  ...
Temperate maize in Iowa        NUE has increased with yield potential                                                 26So...
Summary from past low N research Gains of around 5% per year under low N possible in  “improved” germplasm at yields of 2...
Lessons from the past: soil acidity Acid soils (pH < 5.5) affect 3,950 M ha globally As pH falls Al3+ ions damage roots;...
Aluminum damage                   Susceptible                   Tolerant
Maize grain yield on acid soils         CIMMYT 1975-2008                         Narro, 2011          1975       1994    ...
Principles emerging Most maize populations have a low frequency of stress adaptive alleles, often with small effects Inc...
Looking forward…. Phenotyping is way behind genotyping in cost per dp                      Basics that matter Uniform fie...
Soil electrical conductivity maps help      avoid some field variability             Source: J. Cairns                Chir...
Africa: genetic correlations between target   environments and managed stresses  Target = random abiotic stress with yield...
Africa: breeding approaches: conventional  Preliminary gains: Stage 2 early topcross trials vs. SC403          Southern Af...
Looking forward: sourcesDonors are being identified   CLWN 201 for low N tolerance (G Atlin, IMAS)   For heat and drough...
New secondary traits under evaluation Remote sensing:   The normalized difference vegetation index (NDVI)   Infrared th...
Looking forward: genome wide            selection Conventional + GWS: careful phenotyping and  genotyping by sequencing w...
Genome-wide predictions vs. field      performance in temperate germplasm                   Source: Schussler et al., 2011...
Yield BLUPs for eight conventional        drought tolerant hybrids                   Source: Schussler et al., 2011       ...
Transgenics Drought: MON 87460   Commercial launch in the US in 2012   WEMA: Deploying MON87460 in sub-Saharan Africa  ...
Critical factors for impact Agronomy   Yield potential, input use efficiency   Conservation tillage   Hybrid x managem...
Conclusions….  We could > double impact in stressed environments                            when Tools are integrated: Ge...
44
S1.1 Glimpsing the Future by Looking back : Abiotic Stress Tolerance in Maize
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S1.1 Glimpsing the Future by Looking back : Abiotic Stress Tolerance in Maize

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

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S1.1 Glimpsing the Future by Looking back : Abiotic Stress Tolerance in Maize

  1. 1. Greg Edmeades1, Jill Cairns2, Jeff Schussler3, Amsal Tarakegne2, Stephen Mugo2, Dan Makumbi2 and Luis Narro21 Consultant; 2 CIMMYT; 3 Pioneer Hi-Bred International
  2. 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. 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. 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. 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. 6. If we do nothing and temperature rises in a droughted crop… Source: D. Lobell et al., 2011 6
  7. 7. Variable field environments Source: Kitchen et al., 1999Measured yields ranged from 1 to 10 t/ha 7
  8. 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-1Seeds 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. 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. 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 ininterest in drought tolerance in maize in the last 40 years 10
  11. 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. 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-1Population Drought Unstressed Low N DroughtMaximum 288** 177** 233** -2.1**Minimum 80** 38** 64 ns -0.3**Mean 166 99 166 -1.0Relative yield (%) 30 100 59 30 Source: Edmeades, 2006 12
  13. 13. 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
  14. 14. 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
  15. 15. 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 rainfedGrain 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
  16. 16. Flowering still a vulnerable growth stage GY vs. ASI in elite Corn Belt hybrids 126 elite hybrids, 2 water regimes, 2002
  17. 17. 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
  18. 18. Heat tolerancePossible sources of drought and heat tolerance Source: DTMA Association Mapping Panel (J. Cairns)Drought tolerance does not automatically equate to heat tolerance 19
  19. 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
  20. 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
  21. 21. 22
  22. 22. Response of grain yield to recurrent selection under low and high N (Source: Lafitte and Bänziger 1997, DDLTM: 485-489) 7.5 C0Grain 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
  23. 23. Effect of design and index selection on predicted gains under low N (Source: Bänziger and Lafitte (1997), DDLTM: 401-404) 0.3 137% RCBDPredicted selection response (t ha-1) 116% Lattice 0.2 100% Lat + index 0.1 0.0 RCBD Lattice Lat + index Options 24
  24. 24. 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
  25. 25. Temperate maize in Iowa NUE has increased with yield potential 26Source: USDA, 2009
  26. 26. 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
  27. 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
  28. 28. Aluminum damage Susceptible Tolerant
  29. 29. 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
  30. 30. 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
  31. 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
  32. 32. Soil electrical conductivity maps help avoid some field variability Source: J. Cairns Chiredzi, Zimbabwe 33
  33. 33. 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
  34. 34. Africa: breeding approaches: conventional Preliminary gains: Stage 2 early topcross trials vs. SC403 Southern Africa (N=88) Source: A. Tarekegne 35
  35. 35. Looking forward: sourcesDonors 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
  36. 36. 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
  37. 37. 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
  38. 38. 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
  39. 39. Yield BLUPs for eight conventional drought tolerant hybrids Source: Schussler et al., 2011 Drought No drought stress stressOptimum® AQUAmaxTM 6.89 11.94 (t/ha)Leading checks (t/ha) 6.56 11.59Difference (t/ha) 0.33 0.35 N 223 >1200Improvement (%) 5.0 3.0 Sites in high plains of the US (NE, KS, CO, MO, TX) 2008-10 40
  40. 40. 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
  41. 41. 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
  42. 42. 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-publicWe have the tools. The game is ours to lose 43
  43. 43. 44
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