Breeding maize, rice and wheat for highly variable abiotic stress environments. Marianne Bänziger

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1 Breeding maize, rice and wheat for highly variable abiotic stress environments Marianne Bänziger Gary Atlin Richard Trethowan CIMMYT IRRI => CIMMYT CIMMYT => University of Sydney

2 Question You can breed maize, rice and wheat for highly variable abiotic stress environments.... But can you make progress?

3 Africa - The extreme example for a highly variable abiotic stress environment Rainfall Rainfall and maize yields E&S Africa Rainfall (mm) Rainfall Maize yield Maize yield (t/ha) Year

4 Maize growing environments in Africa GxE analysis Rainfall Tmax N supply Low ph Abiotic stresses Other factors: Biotic stresses Little use of fertilizer and other inputs Setimela et al (2005)

5 Grain yield variability by country Trend adjusted CV 80% 70% 60% 50% 40% 30% 20% Africa Asia Latin America US & Canada Europe 10% 0% Grain yield (t/ha) FAOSTAT, 2006

6 Breeding for highly variable abiotic stress environments The history Abiotic stress environments Low heritability Large GxE Low genetic variance, small potential gains Complex, polygenic tolerance mechanisms - large GxG How to make progress? Spring wheat data from Australia (Bänziger and Cooper, 2001)

7 The Abiotic Stress Breeder

8 Given that few people want to fight wind mills There is one way of getting high yield, 10,000 ways of getting low yields hence I select under optimal conditions to not have to bother with GxE Yield of the variety (t/ha) Variety 1 Variety 2 => Breeding under high potential conditions => Genotype + Inputs => A Green Revolution that bypassed stress prone and low input environments Mean yield of the environment (t/ha) stressed unstressed

9 Perceptions Traditional approaches to breeding crop plants with improved abiotic stress tolerances have so far met limited success (Richards, 1996). One of the most frequently used sentences in grant proposals. FYI, it s quite suitable to justify most research

10 But is it true? Breeding progress or US hybrids selected between 1930s and 1990s Yield gain under favorable conditions Yield gain under mild drought stress 84 kg ha -1 yr kg ha -1 yr -1 Duvick, 1997

11 Breeding progress under abiotic stress conditions in the US Interpretation by the seed industry (Bruce et al., 2002) Use of nurseries with no available irrigation Use of high density Large scale (>1000 locations) broad area testing combined with stability analysis Consistent feed-back from sales figures to breeding => Steady increase in maize grain yields under abiotic stress conditions in the US

12 More recent investments (Löffler et al., 2005) Pioneer, 2006 Use of responsive GIS/crop simulation to characterize the target population of environments Evaluation of 100 to >1000 genotypes at 100 to >1000 locations Weigh G based on the importance of E across years Select the best E G Progress: h * r G * i * σ G Requisite: $$,$$$,$$$

13 Breeding for individual abiotic stresses CIMMYT Started in the 1970s to improve maize for individual abiotic stresses such as drought, low N, low ph Introduced the concept of managed stress environments NOT to simulate a farmers field BUT to simulate a stress that is highly relevant in farmers fields

14 Concept of managed abiotic stress environments Genetic correlation low N - high N Bänziger et al., Yield reduction under low N

15 Concept of managed abiotic stress environments Genetic correlation low N - high N Bänziger et al., Yield reduction under low N

16 Stress management for drought tolerance screening in maize Plant number *** Germination Pre-flowering Flowering Post-flowering Leaf area *** * Leaf senescence * ** *** ASI * *** Ear number *** Grain number per ear Kernel size *** Yield *** * *** ** Breeding progress * ** *** *** ***

17 Breeding for individual abiotic stresses (Edmeades et al., 1996;) Frequency (%) severe drought intermediate drought La Posta wellwatered Grain yield (t ha -1 ) Selection drought tolerance conventional

18 Breeding for individual abiotic stresses Research on Drought, low N, low ph Average breeding progress for target stress: ~100 kg ha -1 yr -1 What farmers grow today Drought tolerant

19 What changed? Water uptake WUE Osmotic adjustment Roots Stress literature Reproductive structures Minor changes Biomass Water uptake Nutrient uptake Large changes Harvest index Internal use of resources Bänziger et al. 1999; 2002; Bolaños & Edmeades, 1993a; 1993b; Bolaños et al., 1993; Edmeades et al., 1999; Lafitte & Edmeades, 1994a; 1994b; 1994c

20 Genetic basis for maize drought stress tolerance (Ribaut et al) C1 C2 C3 C4 C5 C6 C7 C8 C9 C10

21 Question Progress for individual abiotic stresses is possible What is the impact in a highly variable stress prone environment?

22 Hypothesis: Mega trait-based index selection 1. Prioritize abiotic and biotic stresses in the target environment 2. Manage those stresses on the experiment station 3. Apply index selection to large numbers of G 4. Progress = h * r G * i * σ G

23 Mega trait-based index selection by CIMMYT in southern Africa Management Season Sites Selection criteria Selection pressure Same genotypes Recommended input application / high rainfall Managed low N Main 1 Main 1-2 Yield, MSV, GLS, Et, Ps, ear rots, lodging, husk cover Yield, ASI, leaf senescence, ears per plant, ear rots Managed drought Dry 1 Yield, ASI, leaf senescence, 1 ears per plant 1 1 Location: Zimbabwe, 1-2 years; genotypes per year Weigh various traits based on their (assumed) importance in the target environment (= southern and eastern Africa)

24 SI INDIVIDUAL TRAITS LINE AVG YP LOWN DRT ASI EPO RL SL HC PS ET TEX [K64R/CML444]-B-40-# ZM621A BB ZM621A BB ZM423A [CML198/ZSR923S4BULK-2-2-X-X-X [CML445/ZM621B] BB [CML198/LPSC3H #-BB [CML441/CML444]-B-7-# ZM623A ZM521B BB ZM623B SADVIB ZM523A SADVIB ZM523B [EEDMRSR/ZM523B] SADVIB SADVIB ZM623B [P1/P2]RIL B [CML441/CML444]-B-7-# [P1/P2]RIL B [P1/P2]RIL B [H16/K64R]F B [P1/P2]RIL B

25 Are we just fighting windmills?

26 Evaluation of stress breeding approach Stress breeding approach: Yield potential Disease resistance Drought tolerance Low N tolerance Classical breeding approach: Yield potential Disease resistance Extensive multi-loation testing => 42 hybrids from CIMMYT => 41 hybrids from the private seed sector (Monsanto, Pannar, Pioneer, Seed-Co, ZamSeed) All hybrids ever evaluated in regional trials

27 Evaluation in S&E Africa 42 experimental hybrids 41 private company checks trials, 3 years

28 Percentage yield increase of experimental hybrids (n=42) over checks (n=41) 25% Yield increase over checks 20% 15% 10% 5% 0% + *** *** *** *** *** * * *** >9 Average trial yield (t/ha) + Trial #: Note: no maturity differences between experimental hybrids and checks (Bänziger et al., 2006)

29 Conclusion Proof that a focused and relative inexpensive breeding approach can deliberately increase maize yields in a highly variable stress-prone environment 3-4 managed selection environments in Zimbabwe sampling 2 abiotic and 5 biotic stresses 15-20% yield increase under random stress in S&E Africa across all genotypes ever selected

30 Best genotypes: 100% yield increase under stress 14.0 Yield of thr variety (t/ha) Yield of the trial (t/ha) Experimental Checks

31 Effect of different breeding strategies Yield of the variety (t/ha) Mean yield of the environment (t/ha) Variety 1 Variety 2 stressed unstressed

32 Effect of different breeding strategies Yield of the variety (t/ha) Variety 1 Variety 2 Variety 3 Variety 4 Mean yield of the environment (t/ha) stressed unstressed

33 What about other crops? - Drip irrigation to stress wheat nurseries in NW Mexico Stress is monitored and irrigation applied as required Sowing into dry soil: germinated with 40mm of water

34 Associations among managed stress environments, irrigation systems and international test sites (spring bread wheat) Group Stress generated in Mexico Gravity continuous stress Drip Gravity Terminal No stress Stress Drip Continuous stress Heat and terminal moisture stress Drip Moisture stress preflowering Gravity terminal stress International Sites Brazil Spain Algeria Bolivia Pakistan No sites No sites Saudi Arabia Argentina South Africa Egypt Canada Zimbabwe Iran Pakistan Nepal Brazil Pakistan Iran Canada Iran Bangladesh Saudi Arabia Spain Afghanistan

35 Selection of synthetic wheat under managed drought stress Synthetic derivative Synthetic wheat: AB+D (T. durum + T. tauschii) High yielding recurrent parent

36 Percentage of wheat synthetic derivative lines significantly higher yielding than the best locally adapted cultivars in dry environments in Australia (19 sites) and Mexico (CIANO across 3 years) Percentag e CIANO AUS 1 AUS 2 Source: Dreccer et al. Number of derivatives tested = 156 AUS3 AUS 4 AUS5 CIANO AUS6 AUS 7 AUS8 AUS 9 AUS10 AUS11 AUS12 AUS13 CIANO AUS14 AUS15 AUS16 AUS17 AUS18 AUS19

37 Selection for drought tolerance in rice Raipur, 2002 Raipur, 2003 Rainfed rice environments are highly variable across seasons

38 Selection for drought tolerance in rice 5 4 Grain yield (t ha -1 ) Average seasonal field water stress Thailand , Haefele et al.

39 Managed stress screening for rice

40 Variance components and broad sense heritability (H) within water regimes: IRRI dry season 2003/04 Variance component Water regime Genotype Genotype x year Error H Full irrigation 262,360 95, , Reproductive-stage drought 441,810 81, , G x Y not greater in managed stress trials; H similar in stress and non-stress trials

41 Yield (kg/ha) of short-duration lines from the IRRI- India Drought Breeding Network: Raipur 2005 Designation Severe Stress Moderate Stress Control DGI IR Lalmati (trad.) Ramjiyawan (trad.) IR IR LSD Drought-selected lines DGI 75 and IR74371 out-yield IR64 and IR36 under stress and are more responsive than traditional varieties

42 Variance component analysis for drought yield QTL on chromosome 12 in Vandana/Way Rarem Component Estimate Variance of QTL 28,120 Residual genetic variance 29,890 QTL x year 3,670 Residual genetic variance x year 14,250 Plot residuals 62,640 H 0.70 R In many tolerant x susceptible crosses, one or two QTLs appear to account for much of the variation in yield under stress or aerobic conditions

43 Drought yield QTL for Vandana/Way Rarem A single QTL on chromosome 12 accounted for more than 50% of yield variation under severe upland stress over two years (Bernier et al., in press) Allele more than doubles the mean yield under stress (from approximately 0.2 to 0.6 t ha -1 ) Drought tolerant allele originates from the less tolerant parent, Way Rarem => epistasis

44 Conclusions Selection using managed abiotic stress environments enables significant breeding progress in highly variable abiotic stress environments These yield increases are greater than those currently reported for transgenic drought tolerance (100% vs 25%) Some surprises - major gene effects in rice Use of wide crosses in wheat Methods and Genetics

45 Managed environment research site at Pioneer (Albertsen, 2006)

46 Rewriting the history of breeding for abiotic stress tolerance Breeding: low heritability and genetic variance under abiotic stress, large GxE 1975 => No point to breed under abiotic stress + Physiology: As many physiologists as many suggestions what breeders should do 1985 => Little impact on applied stress breeding + GxE analysis + IT + cross-disciplinary collaboration 1995 => Emerging (understanding of) impact on stress breeding + Biotech + High throughput systems 2005 => Transgenic technologies => Increasing progress from non-transgenic abiotic stress breeding

47 Abiotic stress breeding in 2015 It may all be about news coverage Drought resistant crops are on the way (Pioneer and Monsanto, August 2005) Farm News - Drought tolerant corn (Oct 2005) Monsanto develops drought tolerance (Nov 2005) 2-Plants: BASF planning biotech potato and drought-tolerant corn (April 2006) and investment Time from discovery to client - transgenics: US$ 100 million CIMMYT s investment discovery to client (1 million ha) in southern Africa: US$ 3.5 million

48 The future Conventional Polygenic, some major gene effects (Progress 50 >100 %) + Transgenics Single gene effects (Progress 15 25%) Wider application of managed stress environments by more breeders Search for major gene effects, exploitation of epistasis Use of molecular markers (example - common SNP platform for maize drought tolerance targeted at Africa) For both approaches, GxG and GxE will remain important => investments in bioinformatics

49 Acknowledgements Great number of colleagues at CIMMYT and IRRI, in NARS and the private seed sector in Africa, India, Australia and the US Financial supporters: SDC, the Rockefeller Foundation, GRDC