Effects and Interactions of Wheat Leaf Rust Adult Plant Resistance Genes in Uruguay

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P. Silva, V. Calvo-Salazar, F. Condón, M. Quincke, C.
Pritsch, L. Gutiérrez, A. Castro, S. Herrera-Foessel, J.
von Zitzewitz and S. Germán

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Effects and Interactions of Wheat Leaf Rust Adult Plant Resistance Genes in Uruguay

  1. 1. mpsilva@inia.org.uy Effects and interactions of wheat leaf rust adult plant resistance genes in Uruguay P. Silva, V. Calvo-Salazar, F. Condón, M. Quincke, C. Pritsch, L. Gutiérrez, A. Castro, S. Herrera-Foessel, J. von Zitzewitz and S. Germán BGRI Workshop 19-22 August 2013 New Delhi, India
  2. 2. § Introduction § Objective § Materials and methods § Results and Discussion § Conclusions § Future works Outline
  3. 3. INTRODUCTION
  4. 4. URUGUAY Uruguay - South America (34ºS, 55ºW) Wheat area Regional: 6 million has Uruguay: 0.5 million has 54 % of S, MS and I cultivars DIEA, 2013 Leaf rust: most important and widespread wheat rust §  High dynamism of the pathogen population §  Short duration of resistance §  Cultivar replacement Genetic resistance is the best strategy to control LR Increase use of slow rusting resistance (durable)
  5. 5. Slow rusting genes For leaf rust: §  Lr34/Yr18/Pm38/Sr57/Bs: 7DS §  Lr46/Yr29/Pm39/Sr58: 1BL §  Lr67/Yr46: 4BL §  Lr68: 7BL For stem rust: §  Sr2/Yr20/Lr27: 3BS Pleiotropic effect or linkage Combinations of 4 - 5 of these genes results in near immunity Most reported to have differential expression at different temperatures
  6. 6. Environmental effect on LR resistance Principal component analysis of leaf rust severity of Avocet-S x Parula population in South America and Mexico Germán et al. 2010 PC1:59.8% PC2:13.0% Differential expression of resistance genes present in Parula under different environments Mexico Southern Cone
  7. 7. Environmental effect on LR resistance 0 10 20 30 40 50 60 70 80 LR  Cluster  1 LR  Cluster  2 LR  Cluster  3 %  disease  severity none only  Lr46 only    LrP only  Lr34 Lr46+LrP Lr46+Lr34 LrP+Lr34 Lr46+LrP+Lr34 uster  2 LR  Cluster  3 none only  Lr46 only    LrP only  Lr34 Lr46+LrP Lr46+Lr34 LrP+Lr34 Lr46+LrP+Lr34 Nogenes Lr46 Lr68 Lr34 Lr46+Lr68 Lr46+Lr34 Lr68+Lr34 Lr46+Lr68+Lr34 MEXICO 1997, 1998 §  Lr46, Lr68: moderate effect §  Lr34: most effective Modified from Lillemo et al. 2011 0 10 20 30 40 50 60 70 80 LR  Cluster  1 LR  Cluster  2 LR  Cluster  3 %  disease  severity Nogenes Lr46 Lr68 Lr34 Lr46+Lr68 Lr46+Lr34 Lr68+Lr34 Lr46+Lr68+Lr34 URUGUAY 2005 to 2007 ARGENTINA 2007 0 10 20 30 40 50 60 70 80 LR  Cluster  1 LR  Cluster  2 %  disease  severity §  Lr46: no effect §  Lr68: most effective §  Lr34: moderate effect
  8. 8. The expression of the slow rusting genes vary under different environments Environmental effect on LR resistance Which are the genes and specific gene combinations that are most appropriate to reduce LR in different target environments
  9. 9. Objective Investigate the presence, relative effects and interactions of durable resistance genes present in Parula on leaf rust severity by using linked molecular markers in two BC1F6 populations in Uruguay
  10. 10. MATERIALS AND METHODS
  11. 11. LE2304*2/Parula: 73 BC1F6 lines – Population 1 ORL99102*2/Parula: 69 BC1F6 lines – Population 2 Resistant donor: Parula - México (CIMMYT) Adapted - previously described as susceptible to LR - presence of slow rusting genes: unknown LE2304 – Uruguay (INIA) ORL99192 – Brazil (OR-Sementes)   Lr34, Lr46, Lr68 and Sr2 ( Singh et al., 2011; Herrera-Foessel et al., 2012) Plant Material
  12. 12. Phenotypic characterization of LR in the field Plots : 1m row Spreaders rows P. triticina race : TFT-10,20 Virulent to: parents, Lr14b, Lr27+31 (seedlings) Lr13 (adults) Two locations: §  La Estanzuela (34.3° S, 57.7° W, 70 masl) §  Young (32.7° S, 57.6° W, 76 masl) Experimental design: §  incomplete augmented block with two reps §  nine repeated checks
  13. 13. Phenotypic characterization of LR in the field §  Disease severity (DS) was scored using the Modified Cobb Scale §  Four DS scores were taken every 7 to 14 days §  The area under the disease progress curve (AUDPC) was calculated using the following equation:   Peterson et al. 1948 AUDPC= ∑n i=1 [(LRSi + LRSi+1)/2] × (ti+1 – ti)
  14. 14. Genotypic characterization with molecular markers CIMMYT Protocols, 2005 APR gene Primer name Marker Type Reference Lr34 csLV34 + LR34PLUS STS Lagudah et al. 2006; 2009 Lr46 csLV46G22 CAPS (BspEI ) Lagudah, pers comm Lr68 cs7BLNLRR CAPS (HaeIII ) Herrera-Foessel et al. 2012 Sr2 csSr2 CAPS (BspHI) Mago et al. 2010
  15. 15. Statistical analysis Mixed model – Software R (Package LME4): LR AUDPC means Locations, genotypes and days to heading: fixed effects §  LR underestimated on late maturing genotypes Block and replication: random effects Linear model: §  Gene individual effect §  Gene interaction §  Population x gene interaction Contrasts: §  among average LR AUDPC per gene combination (class) §  p-value <0.05
  16. 16. RESULTS AND DISCUSSION
  17. 17. Susceptible checks and parents §  S checks: AUDPC 4500 or higher §  Parula: highly resistance §  LE2304: intermediate §  ORL99192 : susceptible fDS: final disease severity AUDPC_DS Thatcher Avocet Lalbahadur PARULA LE2304 ORL99192 fDS 89% fDS 99% fDS 99% fDS 5% fDS 58% fDS 93%
  18. 18. Genotypic characterization: parents §  LE2304*2/Parula: Lr68 and Sr2 polymorphic §  ORL99192*2/Parula: Lr34, Lr68 and Sr2 polymorphic + positive allele, - negative allele §  Parents: Lr46 present. Monomorphic
  19. 19. Genotypic characterization: Classes Four genotypic classes Eight genotypic classes 11 31 53 50 38 65 82 80 55 63 92 88 % fDS Average AUDPC: 1324 fDS: 31% Average AUDPC: 2640 fDS: 71% fDS: final disease severity
  20. 20. ANOVA – Linear model
  21. 21. Contrasts: LE2304*2/Parula §  Sr2 alone: no effect §  Lr68 alone: 30% ALRR §  Lr68 + Sr2: 47% ALRR 020004000 a b a c AUDPC_DS Effect of single genes and gene combinations on LR AUDPC Lr34 present in all lines ALRR: AUDPC LR reduction
  22. 22. Contrasts: ORL99192*2/Parula §  Sr2 alone: - 8% ALRR §  Lr34 alone: 13% ALRR §  Lr34 + Sr2: 26% ALRR §  Lr68, Lr34+68, Lr68+Sr2: 35% ALRR §  Lr34+68+Sr2: 57% ALRR 0200040006000 b a c d e ee f AUDPC_DS Effect of single genes and gene combinations on LR AUDPC
  23. 23. §  Local higher effect of Lr68 than Lr34 in reduction of LR §  Sr2 genomic region affected LR AUDPC in certain gene combination depending on genotypic background §  The relevance of combining several slow rusting genes was confirmed §  Increasing the frequency and combing these genes in new breeding lines will be valuable to increase LR resistance in future Uruguayan cultivars Conclusions
  24. 24. Future work in Uruguay §  2013 data §  Yellow rust (Toluca, Mexico 2012) §  INIA-CIMMYT-CSIRO: •  Effect of Lr46: Avocet Lr34 x Avocet Lr46 •  Lr68 Mutants
  25. 25. Funding GRACIAS THANK YOU Richard García Fernando Pereira Noelia Pérez Ruth Scholz
  26. 26. Phenotypic characterization of seedling infection type Singh, 2003 Race: TFT-10,20 §  Four lines showed an intermediate score (IT 2) (Roelfs et al.1992) •  LE2304*2/Parula – Lr68+Sr2: 6%DS •  LE2304*2/Parula – Lr68+Sr2: 5%DS •  ORL99192*2/Parula – “no genes”: 74%DS •  ORL99192*2/Parula – Lr34+Sr2: 42%DS
  27. 27. ANOVA – Mixed model §  G x L: expression of resistance in both locations §  LR underestimated on late maturing genotypes
  28. 28. Results and Discussion: Locations La Estanzuela Young AUDPC_DS §  LR infection was severe in both locations §  Higher disease pressure in Young relative than LE fDS: 59% fDS: 64% fDS: final disease severity
  29. 29. Checks and parents AUDPC_DS 020006000 LE2304 ORL99192PARULA fDS: 5% fDS: 58% fDS: 93% fDS: 89% fDS: 64% fDS: 99% fDS: 99% fDS: 96% fDS: 99%
  30. 30. LE2304*2/Parula ORL99192*2/Parula AUDPC_DS Populations fDS: 71% AUDPC_DS AUDPC_DS fDS: 31%

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