Progress on breeding for drought and heat tolerance in maize

Transcription

1 Progress on breeding for drought and heat tolerance in maize J Cairns, JL Araus, C Sanchez, S Trachsel, R Babu, J Crossa, S Hearne, D Makumbi, S Taitad, C Magorokosho, A Menkir, M Banziger, C Bedoya, PH Zaidi

2 Overview Progress in breeding for heat and drought tolerance Genetic analysis of grain yield under drought and heat stress Effects of 1-MCP on stay green and grain yield under drought Outlook on CIMMYTs current activities for heat screening

3 Susceptibility to heat stress Lobell et al. 2011

4 Increase in maximum temperatures (2050) Thornton et al Kai Sonder/Cairns et al. 2012

5 Drought Drought + heat Grain yield (t ha -1 ) Grain yield (t ha -1 ) Anthesis-silking interval (d) Drought stress Anthesis-silking interval (d) Combined drought and heat stress

6 Sensitivity of maize to high temperatures Reduced pollen viability Reduced pollen shed

7 Sensitivity of maize to high temperatures Pollen shed duration Grain yield (t ha -1 ) Anthesis-silking interval (d) Pollen quality (shed & duration) Zimbabwe, 2011 Fonseca and Westgate, 2005

8 Sensitivity of maize to high temperatures Drought Frequency Heat + drought SPAD (2 weeks after anthesis) Chiredzi, Zimbabwe 2011

9 Relationship between combined drought and heat stress Drough t Drought - Drought + heat Drought + Heat Heat Heat Wellwatered Well-watered Cairns et al submitted

10 Future opportunities Semicontrolled (FATE) Field Current breeding pipeline Heat breeding Conservation agriculture Seed production options Tools Germplasm movement Growth regulators Phenotyping Germplasm Management options

11 Identification of heat tolerant donors Phenotyping of the Drought Tolerant Maize for Africa (DTMA) association mapping set Phenotyping in 5 countries across 3 years Drought, heat, combined drought and heat stress, well-watered

12 Evaluation of DTMA germplasmunder abiotic stress Test environment No.of trials Grain yield (t ha -1 ) VG VGE VE H Optimal Managed drought Managed drought + heat

13 Effect of heat stress on grain yield Year Temperature Optimal T High T Optimal T High T Supra-High T GY, WW (t ha -1 ) * GY, DS (t ha -1 ) * % % % - LPSC7F /CML312SR * CML444/CML312* ASI (DS) LSD (5%) H *Adjusted means (BLUPS)

14 Effect of heat stress on grain yield Year Temperature Optimal T High T Optimal T High T Supra-High T GY, WW (t ha -1 ) * % GY, DS (t ha -1 ) * LPSC7F /CML312SR * CML444/CML312* % ASI (DS) LSD (5%) H *Adjusted means (BLUPS)

15 Effect of heat stress on grain yield Year Temperature Optimal T High T Optimal T High T Supra-High T GY, WW (t ha -1 ) * GY, DS (t ha -1 ) * LPSC7F /CML312SR * CML444/CML312* ASI (DS) LSD (5%) H *Adjusted means (BLUPS)

16 Effect of heat stress on grain yield Year Temperature Optimal T High T Optimal T High T Supra-High T GY, WW (t ha -1 ) * GY, DS (t ha -1 ) * LPSC7F /CML312SR * CML444/CML312* ASI (DS) LSD (5%) H *Adjusted means (BLUPS)

17 Ensuring drought tolerant germplasm for future environments Grainyield(t h -1 )* Grain yield (rank) # Wellwatered Drought + Rank Pedigree Drought heat Heat 1 DTPYC9-F La Posta Seq C7-F CL-G1628=G16BNSeqC0F La Posta Seq C7-F La Posta Seq C7-F DTPWC9-F La Posta Seq C7-F DTPYC9-F La Posta Seq C7-F [CML-384 X CML-176]F *Adjusted means (BLUPS) # 300 entries within trial

18 Identification of heat tolerant donors Combined heat and drought tolerance Pedigree GY (t ha -1 ) CML311/MBR C3 Bc F DTPYC9-F La Posta Seq C7-F CLA DTPYC9-F CML412(check) 0.19 Trial mean 0.24 Pedigree GY (t ha -1 ) DTPWC9-F CML497=[CL-00331*v]-3-B La Posta Seq C7-F DTPYC9-F Heat stress tolerance Trial mean 1.50

19 Drought donors (with heat tolerance)

20 Cluster Analysis Well-watered Drought Drought+heat Heat Distance

21 PCA for genetic correlations matrix Well-watered Drought Drought+heat Heat PC2 (21.4 %) PC1 (34.9 %)

22 Structure in DTMA-AM panel PC Eigenvalue PCA analysis based on 55K SNPs No pronounced structure in the DTMA-AM panel first 10 PCs explain ~ 50% of the variation

23 DTMA-AM panel and 55K SNPs can identify large effect genes 1. Grain Color Psy1 R² = 37% Psy2 R² = 14% 92 Yellow lines (1) 186 white lines (0) SNP with largest significant association with grain color located within one of the exons of Phytoene Synthase1 (psy1) on chr.6

24 DTMA-AM panel and 55K SNPs can identify large effect genes 2. QPM Ask2? R² = 8% Opaque2 at 7.01 R² = 16% 10 QPM lines (1) 268 Normal lines (0) Besides opaque-2 and ask-2, several minor QTL regions influencing kernel modification and tryptophan content identified that overlap with previously reported regions

25 Haplotype based association analysis for GY under stress (drought) 5.8% 5.5% 5.1% 7.0% 5.7% 7.3% 5.7% 6.2% 5.1% 4.9% 50K SNPs were reduced to 10K haplotype blocks and association test was performed correcting for population structure using principal components and results validated with mixed linear model analysis (kinship + structure) Only 47 SNPs (~15 genomic regions) out of 10,000 had R 2 values more than 5% Raman Babu

26 Haplotype based association analysis for GY under combined drought + heat Noise levels are relatively higher under very severe stress condition Significant regions such as those on chr.10, chr.9, chr.4 and chr.7 also got identified in the severe stress condition Raman Babu

27 Plant growth regulators (recap) Summary of experiment Genotypes: 1 (DTPYC9-F ) Water treatments: well-watered and drought stress Chemical Treatments: control (water), 1-MCP (single dose of 10 g ai ha-1 and double dose 20 g ai ha-1), ethephon (single dose of 1.5 l ha-1 and double dose of 3 l ha-1) Application time: 1 week before anthesis or 10 days after anthesis Well-watered (WW) Drought stress (DS) Results 1) No significant differences between control and chemical treatments under WW conditions 2) Drought stress reduced grain yield by ~76 % relative to WW control 3) Yields under DS were significantly higher with a single dose of 1-MCP applied prior to and after anthesis, and a double dose Ethephon applied after anthesis

28 Plant growth regulators Summary of experiment Genotypes: 6; Water treatments: 2 (well-watered and drought stress); Chemical treatments: 9 Sowing date: 14 th Feb 2011 Treatment Chemical Dose Timing Entr y Genotypes Genotype 1 DTPYC9-F /CML LPSC /CML-495 Chemical treatments 1 Control - Before anthesis 2 Control - After anthesis 3 1-MCP Single a Before anthesis 3 2A120 (Dow) 4 (CML-269/CML-264)//CML CML-442/CML DTPYC9-F / CML- 539 a 10 g ai ha -1 b 20 g ai ha MCP Double b Before anthesis 5 1-MCP Single After anthesis 6 1-MCP Double After anthesis 7 Ethephon Single c Before anthesis 8 Ethephon Double d Before anthesis 9 Ethephon Single After anthesis

29 Plant growth regulators Grain yield (t ha -1 ) Grain yield (t ha -1 ) DTPYC9-F /CML-451 2A120 (Dow) LPSC /CML-495 (CML-269/CML-264)//CML-494 WW DS Treatment Treatment Treatments 1: Control (before anthesis); 2: control (after anthesis); 3: 1-MCP (single app, before anthesis); 4: 1- MCP (double app, before anthesis); 5: 1-MCP (single app, after anthesis); 6: 1-MCP (double app, after anthesis_; 7: Ethephon (single app, before anthesis); 8: Ethephon (double app, before anthesis); 9: Ethephon (single app, after anthesis)

30 Plant growth regulators Grain yield (t ha -1 ) CML-442/CML-444 DTPYC9-F / CML-539 WW DS Treatment Treatment Results 1) Drought stress reduced grain yield by 60% relative to the WW control 2) No significant differences in grain yield between chemical treatments under WW and DS conditions 3) No significant difference in the % reduction in GY relative to the WW control between chemical treatments

31 Plant growth regulators Results 1) Under drought stress 1-MCP delayed senescence (estimated through NDVI) 18 and 25 days relative to the control (p<0.01) 2) There was no significant genotype*treatment interaction 3) No significant difference in NDVI was identified 32 days after anthesis 18 days after anthesis 25 days after anthesis NDVI Treatment Treatment Treatments 1: Control (before anthesis); 2: control (after anthesis); 3: 1-MCP (single app, before anthesis); 4: 1- MCP (double app, before anthesis); 5: 1-MCP (single app, after anthesis); 6: 1-MCP (double app, after anthesis_; 7: Ethephon (single app, before anthesis); 8: Ethephon (double app, before anthesis); 9: Ethephon (single app, after anthesis)

32 Can landraces help improved tolerance to drought and high temperatures?

33 Evaluation of landraces under WW and DS

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35 Status

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37 Cluster analysis for 38 Mexican populations

38 Use of accesionsin breeding

39 Summary - Different Mechanisms allow plants to cope with drought, high temperatures - Accordingly there is only little overlap between germplasm tolerant to the three stresses - In several years of screening under drought, high temperatures CIMMYT has identified hybrids and crosses that are tolerant to these stresses - Tolerant lines are available for partners to be used in their breeding pipeline. - CIMMYT keeps screening germplasm for tolerance to heat in Ciudad Obregon and potentially in Arizona - Attempts are underway to identify alleles conveying tolerance to abiotic stress in landraces