Advances in the research to achieve resistance to wheat rusts

Advances in the Research to Achieve Resistance to Wheat Rusts Sukhwinder-Singh, Ravi Singh, Julio Huerta, Sridhar Bhavani and Sybil Herrera Global Wheat Program, CIMMYT

Outline of the Presentation Introduction Background on resistance to wheat rusts Characterization of resistance Utilization of APR Mapping/ QTL analysis

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

Wheat Research Efforts – CIMMYT Increase wheat productivity - genetic gain Protection – biotic and abiotic stresses(estimated global losses due to pathogenin wheat is 13 billion dollar (~12%)Simultaneously evaluating for Yield (Y) and Stress Tolerant (ST)

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%.

Types of ResistanceMore than170 rust R genes - cataloged in wheat1. Seedling: Monogenic ≈ Race-specific ≈ Major genes ≈ Vertical ≈ Hypersensitive ( Boom & Bust)2. APR: Polygenic ≈ Race-nonspecific ≈ Minor genes≈ Horizontal ≈ Slow rusting/ Partial (Durable)

Boom-and-Bust cycle - Northwestern MexicoVariety Resistance gene Released Breakdown RaceBread Wheat:Yecora 70 Lr1, 13 1970 1973 ?Tanori 71 Lr13, 17 1971 1975 ?Jupateco 73 Lr17, 27+31 1973 1977 TBD/TMGenaro 81 Lr13, 26 1981 1984 TCB/TBSeri 82 Lr23, 26 1982 1985 TCB/TDBaviacora 92 Lr14b, 27+31 1992 1994 MCJ/SP

Genes involved in APR, 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

Durable Resistance Resistance which 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 adisease or pest (Johnson 1988). Example: Frontana, Pavon 76, Parula, andChapio,

Identification and characterization of 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

Breeding for durable, adult-plant resistance at CIMMYTMexico (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

Evaluation and characterization of resistance-Field trials Artificialepidemics Rust Severity (%): Modified Cobb Scale, Peterson et al. 1948) Reaction: R, MR, MS, S

Borlaug Global Rust Initiative A multi-institutional partnership for systematicallyreducing vulnerability of global wheat crop to wheat rustsDurable 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

Methodology used for identifying 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

Genetic basis of resistance 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 ofgenes determining a quantitative trait)

APR genes identified Lr34/Yr18/Pm38/Sr57/Ltn1 Lr46/Yr29/Pm39/Ltn Sr2/Yr30/(Lr27)/Pbc Lr67/Yr46/Pm?/Sr55/Ltn Lr68/Yr?Yr36

Leaf tip Necrosis and 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

Durable adult-plant Pseudo black-chaffresistance (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

Genetic basis of durable resistance to rust diseases of wheat% Rust100 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

Methodology Phenotyping: field s 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

Molecular markers for durable resistanceGene Marker ReferenceSr2/Yr30 gwm533 Crop Sci 43:333–336Lr34/Yr18 CSLV34+ Lr34sp TAG 119:889–898Lr46/Yr29 CSLV46G22*Lr67/Yr46 gwm192, gwm165 TAG 122(1):239-249,Lr68 7BLNRR* TAG 124:1475–1486Yr36 Barc101, Gpc-B1 Science 23:1357-1360Yr48 EST BE495011 TAG 123:143-157

Advances in Molecular Mapping 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

Cloning rust resistance genes in wheatUnderstanding 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

APR pleiotropic resistance gene Lr34/Yr18/Pm38 Perfect marker for Lr34 -veLr34sp & +veLr34spA ABC (ATP Binding Cassette) (multiplex) transporter of PDR (Pleiotropic Drug Resistance) subfamilyCloning 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

AcknowledgementDRRW : BGRI GWP at CIMMYT(Bill and Melinda Eric Eugenio Lopez’sGates Foundation) Sybil Herrera- FoesselSyngenta Pawan K. SinghFoundation Velu Govindan Thank you

Advances in the research to achieve resistance to wheat rusts

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