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Advances in the research to achieve resistance to wheat rusts
Advances in research to achieve resistance to wheat rusts were presented. The presentation discussed the background on resistance to wheat rusts, characterization of resistance including seedling and adult plant resistance, utilization of adult plant resistance, and mapping and QTL analysis of resistance genes. Key advances included the identification of adult plant resistance genes such as Lr34, Lr46, and Sr2, as well as efforts to clone resistance genes to better understand the genetic basis of resistance. International collaborations were also highlighted as important to breed durable rust resistance in wheat.
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Advances in the research to achieve resistance to wheat rusts
- 1. Advances in theResearch to Achieve Resistance to Wheat Rusts Sukhwinder-Singh, Ravi Singh, Julio Huerta, Sridhar Bhavani and Sybil Herrera Global Wheat Program, CIMMYT
- 2. Outline of thePresentation Introduction Background on resistance to wheat rusts Characterization of resistance Utilization of APR Mapping/ QTL analysis
- 3. Present (2011) vs.Future (2025) P o p u la t io n 6 . 8 b illio n 8 . 5 b illio n C onc e rn lim it e d r e s o u r c e s e ne rg y a nd e n v ir o n m e n t a l c o n s u m e r p re fe re nc e C rop a re a L im it e d s c o p e o f i nl a n te b rse e d i n g i n t h i s n e w e r a s h o u l d P c r a e b e m o r e d i v e r s i fPerd s s u r e o n l a n d w i l l i e iP l a nrt e a ese e i n g nc Br d N e w t o o ls o f b io lo g y
- 4. Wheat Research Efforts– CIMMYT Increase wheat productivity - genetic gain Protection – biotic and abiotic stresses (estimated global losses due to pathogen in wheat is 13 billion dollar (~12%) Simultaneously evaluating for Yield (Y) and Stress Tolerant (ST)
- 5. Wheat Rusts –Historic Relevance to Agriculture Productivity Brown (leaf) rust Black (stem) rust Yellow (stripe) rust (Puccinia triticina) Puccinia graminis Puccinia striiformis An epidemic - Susceptible varieties Jupateco 73 in Northwest Mexico Yield losses up to 100% 1976–1977. Yield reductions up to 40%.
- 6. Types of Resistance Morethan170 rust R genes - cataloged in wheat 1. Seedling: Monogenic ≈ Race-specific ≈ Major genes ≈ Vertical ≈ Hypersensitive ( Boom & Bust) 2. APR: Polygenic ≈ Race-nonspecific ≈ Minor genes ≈ Horizontal ≈ Slow rusting/ Partial (Durable)
- 7. Boom-and-Bust cycle -Northwestern Mexico Variety Resistance gene Released Breakdown Race Bread Wheat: Yecora 70 Lr1, 13 1970 1973 ? Tanori 71 Lr13, 17 1971 1975 ? Jupateco 73 Lr17, 27+31 1973 1977 TBD/TM Genaro 81 Lr13, 26 1981 1984 TCB/TB Seri 82 Lr23, 26 1982 1985 TCB/TD Baviacora 92 Lr14b, 27+31 1992 1994 MCJ/SP
- 8. Genes involved inAPR, slow rusting resistance to rust diseases Minor genes with small to intermediate effects Gene effects are additive Resistance does not involve hypersensitivity Genes confer slow disease progress through: 1. Reduced infection frequency 2. Increased latent period 3. Smaller uredinia 4. Reduced spore production
- 9. Durable Resistance Resistancewhich has remained effective in a cultivar during its widespread cultivation for a long sequence of generations or period of time in an environment favorable to a disease or pest (Johnson 1988). Example: Frontana, Pavon 76, Parula, and Chapio,
- 10. Identification and characterizationof slow rusting resistance ● High or susceptible infection type in the seedling growth stage ● Lower disease severity or rate of disease progress in the field compared to susceptible check Brown rust: High (compatible) infection type in the field Yellow rust: Infection type not a reliable criteria due to systemic growth habit Stem rust: Variable size of pustules- bigger near nodes
- 11. Breeding for durable,adult-plant resistance at CIMMYT Mexico (Cd. Obregon-Toluca/El Batan)- Kenya International Shuttle Breeding: a five-year breeding cycle) Cd. Obregón 39 masl High yield (irrigated), Water-use efficiency, Heat tolerance, Leaf rust, stem rust (not Ug99) Njoro, Kenya 2185 masl El Batán 2249 masl Stem rust (Ug99 group) Leaf rust, Fusarium Yellow rust Toluca 2640 masl Yellow rust Septoria tritici Fusarium Zero tillage ● Shuttle breeding between Mexico and Kenya initiated in 2006 ● >1000 F3/F4 populations undergo Mexico-Kenya shuttle ● High yielding, resistant lines from 1st cycle of Mexico-Kenya shuttle under seed multiplication for international distribution in 2010
- 12. Evaluation and characterizationof resistance-Field trials Artificial epidemics Rust Severity (%): Modified Cobb Scale, Peterson et al. 1948) Reaction: R, MR, MS, S
- 14. Borlaug Global RustInitiative A multi-institutional partnership for systematically reducing vulnerability of global wheat crop to wheat rusts Durable Rust Resistance in Wheat Project- Objectives Planning for the Threat of Emerging Wheat Rust Variants Advocating and Coordinating Global Cooperation Tracking Wheat Rust Pathogens Supporting Critical Rust Screening Facilities in East Africa Breeding to Produce Rust Resistant Varieties Developing and Optimizing Markers for Rust Resistance Reducing Linkage Drag Discovering New Sources of Rust Resistance Exploring Rice Immunity to Rust
- 15. Methodology used foridentifying APR to Ug99 in current wheat materials ● Field evaluation of advanced breeding lines in Kenya/Ethiopia ● Greenhouse seedling tests for susceptibility to Ug99 at USDA-ARS Lab. in St. Paul, Minnesota, US ● Characterization of pseudo-black chaff phenotype and application of Sr2 molecular marker ● Identified APR Sources: Kingbird, Kiritati, Juchi, Pavon, Parula, Picaflor, Danphe, Chonte Kingbird-the best source of APR
- 16. Genetic basis ofresistance Evaluation of populations created from crosses: Susceptible parent X resistant parent Number resistance Number of genes conferring resistance Resistant parent1 X Resistant parent2 Allelism test Estimation of genetic diversitya Traditional Mendelian Segregation analysis Quantitative methods (formula for estimation of number of genes determining a quantitative trait)
- 17. APR genes identified Lr34/Yr18/Pm38/Sr57/Ltn1 Lr46/Yr29/Pm39/Ltn Sr2/Yr30/(Lr27)/Pbc Lr67/Yr46/Pm?/Sr55/Ltn Lr68/Yr? Yr36
- 18. Leaf tip Necrosisand Slow Rusting Resistance Lr34/Yr18/Pm38, Leaf tip necrosis associated with Lr46 Lr46/Yr29/Pm39 and Lr67/Yr46/Pm? linked to some level of leaf tip necrosis expression Slow rusting resistance without leaf tip necrosis also known Lalbahadur+Lr46 Lalbahadur
- 19. Durable adult-plant Pseudo black-chaff resistance (APR) to stem rust Sr2-Complex (Sr2 and other minor genes) • Sr2 transferred to wheat from ‘Yaroslav’ emmer in 1920s by McFadden • Sr2 is linked to pseudo-black chaff • Sr2 confers only moderate levels of resistance (about 30% reduction in disease severity) • Adequate resistance achieved when Sr2 combined with other unknown genes • Essential to reduce/curtail the evolution of Sr2 present Sr2 absent Ug99 in East Africa and other high risk areas
- 20. Genetic basis ofdurable resistance to rust diseases of wheat % Rust 100 Susceptible 80 1 to 2 minor genes 60 40 2 to 3 minor genes 20 4 to 5 minor genes 0 0 10 20 30 40 50 Days data recorded Relatively few additive genes, each having small to intermediate effects, required for satisfactory disease control Near-immunity (trace to 5% severity) can be achieved even under high disease pressure by combining 4-5 additive genes
- 21. Methodology Phenotyping: fields eas ons A rtificial epidemic s Rus t s everity rec orded when 80-100% dis eas e on mos t s us ceptible RILs G enotyping: DA rT and S S R markers QTL analys is : - IC IM) - Q-gene 1 2 3 4 5 6
- 22. Molecular markers fordurable resistance Gene Marker Reference Sr2/Yr30 gwm533 Crop Sci 43:333–336 Lr34/Yr18 CSLV34+ Lr34sp TAG 119:889–898 Lr46/Yr29 CSLV46G22* Lr67/Yr46 gwm192, gwm165 TAG 122(1):239-249, Lr68 7BLNRR* TAG 124:1475–1486 Yr36 Barc101, Gpc-B1 Science 23:1357-1360 Yr48 EST BE495011 TAG 123:143-157
- 23. Advances in MolecularMapping of Slow Rusting Resistance Genes ● Several Genomic locations (QTLs) known ● Developing and characterizing mapping populations that segregate for single resistance genes Single gene based populations for 2 or 3 undesignated genes now available at CIMMYT Very difficult to characterize populations segregating for minor genes that have relatively small effects ● Gene-based markers for relatively larger effect slow rusting genes becoming reality Gene Lr34/Yr18/Pm38 cloned and gene-based marker available Significant progress made towards cloning of Lr46/Yr29/Pm39
- 24. Cloning rust resistancegenes in wheat Understanding the structure of the genes and function of proteins Major resistance genes: Lr1(Cloutier et al) Lr10(Feuillet et al) Lr21(Huang et al) APR durable resistance genes: Lr34/Yr18 (Krattinger et al) –ABC transporter Yr36(Fu et al) –Kinase Start gene
- 25. APR pleiotropic resistancegene Lr34/Yr18/Pm38 Perfect marker for Lr34 -veLr34sp & +veLr34spA ABC (ATP Binding Cassette) (multiplex) transporter of PDR (Pleiotropic Drug Resistance) subfamily Cloning of Lr34/Yr18/Pm38 1 2 3 4 5 6 ● Single gene based fine mapping populations • Lalbahadur ● Gamma-ray induced deletion stocks • Lalbahadur+Lr34 • Thatcher ● Azide-induced mutations • RL6058 (Thatcher+Lr34) ● Precision phenotyping • Chinese Spring (+Lr34) • Lr34 deletion mutant ● Partnership (CIMMYT, CSIRO and Univ. of Zurich) Krattinger et al. Science 2009
- 27. Acknowledgement DRRW : BGRI GWP at CIMMYT (Bill and Melinda Eric Eugenio Lopez’s Gates Foundation) Sybil Herrera- Foessel Syngenta Pawan K. Singh Foundation Velu Govindan Thank you
Editor's Notes
- #4 Bread wheat provides ~20% of the calories consumed by humankind. The increasing world demand, limite resources, climate changing ------- improve strategies to increase genetic gain (yield) and also to reduce yield lossess due to pathogens 06/28/12
- #5 improve strategies to increase genetic gain (yield) and also to reduce yield lossess due to pathogens More than160 resistance genes that confer resistance to rusts of wheat have been cataloged in wheat or introgressed into wheat from related species. These genes in wheat fall under two broad categories and are referred to as seedling and adult plant resistance (APR) genes. Seedling resistance genes are detected during both the seedling and adult plant stages and as such constitute an all stage resistance phenotype. APR is commonly detected at the post-seedling stage and often as field resistance. A large proportion of seedling resistance genes exhibit phenotypes of major effect and with varying infection types whereas most of the APR genes are partial in effect with varying levels of disease severity. 06/28/12
- #6 Wheat rusts affects million of hectares of wheat and virulent races that have appeared within past decade are casuing large yile losses. Wheat rusts are prominent in their historic relevance to agriculture productivity More than160 resistance genes that confer resistance to rusts of wheat have been cataloged in wheat or introgressed into wheat from related species. These genes in wheat fall under two broad categories and are referred to as seedling and adult plant resistance (APR) genes. Seedling resistance genes are detected during both the seedling and adult plant stages and as such constitute an all stage resistance phenotype. APR is commonly detected at the post-seedling stage and often as field resistance. A large proportion of seedling resistance genes exhibit phenotypes of major effect and with varying infection types whereas most of the APR genes are partial in effect with varying levels of disease severity. 06/28/12
- #8 Boom-and-Bust”: Race-Specific Genes for leaf rust resistance in Northwestern Mexico 06/28/12
- #10 06/28/12
- #12 06/28/12
- #20 06/28/12 The top priority at CIMMYT is to restore the “Sr2 gene complex”, i.e., select slow rusting gene Sr2 in combination with other yet unidentified minor genes.
- #21 06/28/12 This figure shows the relationship between number of minor genes and rust progress in field trials. It is likely that 4 to 5 minor genes will be necessary to retard the rust progress to non-significant levels.