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Cereal Rust Diseases
Bob Bowden USDA-ARS Hard Winter Wheat
Genetics Research Unit
Kansas State University
Manhattan, KS
Leaf Crown Stem Stripe
Castroville Rust Nursery
Ug99 Stem Rust in the Headlines
Wheat Leaf Rust: Boom & Bust
0
5
10
15
20
25
Percen
t o
f A
cres
1991 1992 1993 1994 1995 1996 1997 1998 1999 2000
Year
Karl Wheat Cultivar Succumbs to Leaf Rust
0
2
4
6
8
10
12
% L
oss
Year
Stripe Rust Losses - Kansas
Jon Appel, Erick DeWolf, Bill Bockus
Oat Crown Rust
Eric Jackson, ARS, Aberdeen, ID
Erick DeWolf, 2011
Disease Resistance
Highly Susceptible Highly Resistant
Matthew Rouse
How Many Resistance Genes?
• Lr1 to Lr68 for wheat leaf rust
• Yr1 to Yr49 for wheat stripe rust
• Sr1 to Sr53 for wheat stem rust
• Pc-1 to Pc-96 for oat crown rust
SrCad
SrGabo56
Wheat Stem Rust Resistance Loci
1A 2A 3A 4A 5A 6A 7A
1B 2B 3B 4B 5B 6B 7B
1D 2D 3D 4D 5D 6D 7D
Sr9 Sr28
Sr7 Sr13
Sr8
Sr22
Sr36 Sr40 Sr23 Sr39
Sr33 Sr45
Sr35
Sr2
Sr5 Sr6
Sr10
Sr11
Sr12
Sr14
Sr15
Sr16 Sr17
Sr18
Sr19
Sr20
Sr21
Sr24 Sr25
Sr26
Sr27
Sr29
Sr30
Sr31
Sr32
Sr34
Sr37
Sr38
Sr41 Sr42
SrWeb
SrTm4
SrSha7
SrB
SrC
SrNing
Sr44
Sr43
Sr1A.1R
Lr34 SrR
Mike Pumphrey, WSU
Stakman Infection Types
Leonard and Szabo
Adult IT Rating Scale
Xianming Chen
Race Specificity
Isolate 1 Isolate 2
How Many Races?
• Dozens for wheat leaf rust
• Dozens for wheat stripe rust
• Few (mostly just QFCSC) for wheat
stem rust
• Huge number for oat crown rust
Race Identification
Where do new races come from?
Life Cycle of
Puccinia graminis Macrocyclic, heteroecious
Yue Jin, Cereal Disease Lab
Buckthorn Nursery for Oat Crown Rust
Cereal Disease Lab
Xianming Chen, USDA
Long Distance Migration
Cereal Disease Lab
The Puccinia Pathway
Leaf Crown Stem Stripe
Race Diversity Med Med Low* High
Genotypic Diversity Low Low Low* High
Sexual Recombination No No? No* Yes (spring oat region)
Annual Bottlenecks No Yes* Yes* No
R-gene durability Low-Med Low-Med High* Low
* Except in PNW
Mean Virulence of P. coronata f.sp.
avenae in Spring Oat Region
Virulence in Oat Crown Rust (Puccinia coronata f. sp. avenae) in the United States from 2006 through 2009.
M. L. Carson. 2011. Plant Disease 95:1528-1534
Cytogenetics to Reduce Linkage Drag
Bernd Friebe, KSU
Major Gene Strategies
• Use only gene combinations (pyramids).
– Prob(virulence to one gene) = 10-6
– Prob(virulence to two genes) = 10-12
– Prob(virulence to three genes) = 10-18
– Prob(virulence to four genes) = 10-24
– Must have control of all the genes
• Get smarter about finding durable combinations
– Negative associations between virulences
– Clone the effectors and targets and find and
eliminate redundancies
Resistance Types
• Minor gene resistance
• Adult plant resistance
• Slow rusting resistance
• Race-nonspecific
• Quantitative resistance
• Durable resistance
• QTL
• Non-NBS-LRR
• Major gene
• Seedling or all-stage
• Hypersensitive
• Race-specific
• Qualitative
• Non-durable resistance
• R-gene
• NBS-LRR gene
Slow Rusting Genes Identified
• Lr34/Yr18 (7DS)
• Lr46/Yr29 (1BL)
• Lr67/Yr46 (4DL)
• Lr68 (7BL)
• Sr2/Yr30 (3BS)
Lr34 Phenotype
•Lr34/Yr18 was cloned and turned out to be ABC transporter
(Krattinger et al. 2009)
Photo by Bob Bowden
Roelfs F2007 Mexican Variety
Photo by Bob Bowden
Genetic basis of durable resistance to rust diseases of
wheat Susceptible
1 to 2 minor
genes
2 to 3 minor genes
Munal, Picaflor,
Francolin, Pauraque
4 to 5 minor genes
Kingbird
% Rust
Days data recorded
100
80
60
40
20
0
0 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 minor genes
with additive effects
Ravi Singh, CIMMYT
Singh et al, 2011. Ann Rev Phytopathol
Ug99-Resistant Varieties Released or in
Advanced stages of Variety Registration
Acknowledgements
• Xianming Chen
• Erick De Wolf
• Bernd Friebe
• Eric Jackson
• Yue Jin
• Jim Kolmer
• Mike Pumphrey
• Matthew Rouse
• Ravi Singh