Advances in the research to achieve resistance to wheat rusts
1. 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
2. Outline of the Presentation
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
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)
8. 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
9. 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,
10. 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
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 characterization of
resistance-Field trials
Artificial
epidemics
Rust Severity (%): Modified Cobb Scale, Peterson
et al. 1948)
Reaction: R, MR, MS, S
13.
14. Borlaug Global Rust Initiative
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 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
16. 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 of
genes determining a quantitative trait)
18. 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
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 of durable 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: 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
22. 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
23. 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
24. 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 transporter
Yr36(Fu et al) –Kinase Start gene
25. APR pleiotropic resistance gene 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
26.
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
Notas del editor
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
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
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
Boom-and-Bust”: Race-Specific Genes for leaf rust resistance in Northwestern Mexico 06/28/12
06/28/12
06/28/12
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.
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.