Advances in the Research to Achieve Resistance to Wheat

Rusts

Sukhwinder-Singh, Ravi Singh, Julio Huerta, Sridhar Ravi Singh, Julio Huerta, Sridhar Bhavani and Sybil HerreraBhavani 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)

Population 6.8 billion 8.5 billion

Concern limited resources energy and

environmental consumer preference

Crop area Limited scope of increase

Pressure on land will increase

Plant breeding in this new era should be more diversified

Plant Breeding New tools of biology

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)

Yellow (stripe) rustPuccinia striiformis

Black (stem) rust Puccinia graminis

An epidemic -Jupateco 73 in Northwest Mexico 1976–1977. Yield reductions up to 40%.

Brown (leaf) rust(Puccinia triticina)

Wheat Rusts – Historic Relevance to Agriculture

Productivity

Susceptible varietiesYield losses up to 100%

Types of Resistance

More than170 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)

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

Genes involved in APR, slow rusting resistance to rust

diseases Minor genes with small to intermediate effectsMinor genes with small to intermediate effects

Gene effects are additiveGene effects are additive

Resistance does not involve hypersensitivityResistance does not involve hypersensitivity

Genes confer slow disease progress through: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 a disease or pest (Johnson 1988).

Example: Frontana, Pavon 76, Parula, and Chapio,

Identification and characterization ofslow 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 maslHigh yield (irrigated), Water-use efficiency, Heat tolerance, Leaf rust, stem rust (not Ug99)

Toluca 2640 maslYellow rustSeptoria triticiFusariumZero tillage

El Batán 2249 maslLeaf rust, Fusarium

Njoro, Kenya 2185 maslStem rust (Ug99 group)Yellow rust

● 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

Artificial epidemics

Rust Severity (%): Modified Cobb Scale, Peterson et al. 1948) Reaction: R, MR, MS, S

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

Durable Rust Resistance in Wheat Project- Objectives

Borlaug Global Rust InitiativeA multi-institutional partnership for systematically

reducing vulnerability of global wheat crop to wheat rusts

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 parentNumber resistance Number of genes conferring

resistance Resistant parent1 X Resistant parent2

Allelism test Estimation of genetic diversity

Traditional Mendelian Segregation analysis

Quantitative methods (formula for estimation of number of genes 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, 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

Leaf tip necrosis associated with Lr46

Sr2 presentSr2 absent

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 Ug99 in East Africa and other high risk areas

Durable adult-plant resistance (APR) to stem

rust

Pseudo black-chaff

Genetic basis of durable resistance to rust diseases of wheat

Susceptible

1 to 2 minor genes

2 to 3 minor genes

4 to 5 minor genes

% Rust

Days data recorded

100

80

60

40

20

00 10 20 30 40 50

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 seasons

Artificial epidemicsRust severity recorded when 80-100%

disease on most susceptible RILs Genotyping: DArT and SSR markers

QTL analysis: - ICIM)

- Q-gene

1 2 3 4 5 6

Molecular markers for durable 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

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 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 transporterYr36(Fu et al) –Kinase Start gene

Perfect marker for Lr34-veLr34sp & +veLr34spA

(multiplex)

1 2 3 4 5 6

1 Lalbahadur 2 Lalbahadur+Lr343 Thatcher4 RL6058 (Thatcher+Lr34)5 Chinese Spring (+Lr34)6 Lr34 deletion mutant

APR pleiotropic resistance gene Lr34/Yr18/Pm38

Cloning of Lr34/Yr18/Pm38● Single gene based fine mapping populations● Gamma-ray induced deletion stocks● Azide-induced mutations● Precision phenotyping● Partnership (CIMMYT, CSIRO and Univ. of Zurich)

ABC (ATP Binding Cassette) transporter of PDR (Pleiotropic Drug

Resistance) subfamily

Krattinger et al. Science 2009

Acknowledgement

DRRW : BGRI(Bill and Melinda Gates Foundation)

Syngenta Foundation

GWP at CIMMYTEric Eugenio Lopez’sSybil Herrera-Foessel Pawan K. SinghVelu Govindan Thank you