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