# Presentation: 317901

## Resistance to Stem Rust Race TTKS Maps to the rpg5/Rpg5 Complex of Chromosome 7(5H) of Barley

**Brian Steffenson, Yue Jin,**
** ****Robert Brueggeman and Andris Kleinhofs**
**University of Minnesota, St. Paul**
**Washington State University, Pullman**

## Race TTKS (Ug99) was first discovered in 1999 in Uganda and has since spread to Kenya (2001), Sudan (2006) and Yemen (2006)

Percentage of wheat cultivars susceptible to TTKS worldwide ranges from 30% to over 90% across different regions

This race is a threat to global food security

- Percentage of wheat cultivars susceptible to TTKS worldwide ranges from 30% to over 90% across different regions
- This race is a threat to global food security

**Race TTKS**

## 
Barley is a host to both wheat stem rust and rye stem rust

Susceptible to race TTKS

With its early maturity, barley may 
    act as an early inoculum source 
    for wheat
Barley is a significant food crop in
   many of the same areas where
   wheat is threatened: ETH & ERI 

- Barley is a host to both wheat stem rust and rye stem rust
- Susceptible to race TTKS
- With its early maturity, barley may
-     act as an early inoculum source
-     for wheat
- Barley is a significant food crop in
-    many of the same areas where
-    wheat is threatened: ETH & ERI

**Race TTKS and Barley**

## All of the Upper Midwest barley cultivars have been bred with Rpg1

This gene has protected barley from damage due to stem rust since the late 1940s

But...Rpg1 is ineffective against race TTKS

- This gene has protected barley from damage due to stem rust since the late 1940s
- But...*Rpg1* is ineffective against race TTKS

**Race TTKS and Midwest Barley**

## Various Hordeum accessions were assessed for their reaction to race TTKS in the greenhouse

This germplasm included cultivated (Barley CAP, other breeding lines, and cultivars), Swiss landraces, and wild barley

- This germplasm included cultivated (Barley CAP, other breeding lines, and cultivars), Swiss landraces, and wild barley

**Evaluation of *****Hordeum***** to Race TTKS**

## Race TTKS Resistance  Cultivated Germplasm

| General Class | # | % |
| --- | --- | --- |
| Resistant | 0-16 | 0.0-16.7 |
| Mod. Resist |  2-13 |   2.0-13.5 |
| Mod. Suscept |  14-26 | 14.6-27.1 |
| Susceptible
 | 12-65 | 12.5-67.7 |

**Barley CAP Germplasm: 960 Accessions from  10 Different Programs**

## Race TTKS Resistance  Swiss Landraces

| General Class | # | % |
| --- | --- | --- |
| Resistant | 57 | 77.0 |
| Mod. Resist |  7 |   9.5 |
| Mod. Suscept |  0 | 0 |
| Susceptible
 | 10 | 13.5 |

**74 Accessions **

## Race TTKS Resistance  Wild Barley

| General Class | # | % |
| --- | --- | --- |
| Resistant | 5 | 25.0 |
| Intermediate  | 3 | 15.0 |
|  |  |  |
| Susceptible
Variable  | 7
5 | 35.0
25.0 |

**20 Accessions **

**Resistant accessions from Israel, W. Tajikistan and**
**E. Uzbekistan**

## Vulnerability of Barley Stem Rust

- Race QCC arose in 1989; carried virulence for *Rpg1*
- From over 18,000 accessions  evaluated, only a few exhibited a high level of adult plant resistance to pathotype QCC

## CIMMYT/ICARDA derived line with unknown pedigree

Selection made by Roger Boyd in Mexico

Resistance first found to race QCC by Alan Roelfs

Inheritance studies made and a single recessive gene, rpg4, was found to confer resistance to race QCC

- Selection made by Roger Boyd in Mexico
- Resistance first found to race QCC by Alan Roelfs
- Inheritance studies made and a single recessive gene, *rpg4*, was found to confer resistance to race QCC

**Barley Line Q21861**

## Additional evaluations of Q21861 revealed resistance to rye stem rust in addition to QCC

Subsequent genetic analyses showed co-segregation of rye stem rust resistance and QCC resistance; thus the same gene appeared to control resistance to both rusts

However, resistance to rye stem rust acted in a dominant fashion instead of recessive as with race QCC

- Subsequent genetic analyses showed co-segregation of rye stem rust resistance and QCC resistance; thus the same gene appeared to control resistance to both rusts
- However, resistance to rye stem rust acted in a dominant fashion instead of recessive as with race QCC

**Barley Line Q21861**

## Q21861 was tested at the seedling stage to race TTKS in 2005 and was found to possess a high level of resistance

This resistance was confirmed at the adult plant stage in the field in Kenya

The Q21861/SM89010 population was then screened to race TTKS to investigate the inheritance of resistance

- This resistance was confirmed at the adult plant stage in the field in Kenya
- The Q21861/SM89010 population was then screened to race TTKS to investigate the inheritance of resistance

**Barley Line Q21861**
**Reaction to Race TTKS**

## Q21861 and SM89010 Parents

**Q21861 and SM89010 Parents**
**Reaction to Race TTKS**

**Q28161**

**SM89010**

## Q21861/SM89010

**Q21861/SM89010**
**Reaction to Race TTKS**

| Race | Resist | Suscept | Ratio | X2 | Prob>X2 |
| --- | --- | --- | --- | --- | --- |
| QCCJ | 56 | 69 | 1:1 | 1.35 | 0.24 |
| TTKS | 56 | 69 | 1:1 | 1.35 | 0.24 |

## Chromosome 7(5H) of Barley

- MWG920.1A

**Resistance to race QCC (*****rpg4*****), rye**
**stem rust isolate 92-MN-90 (*****Rpg5*****), and race TTKS (*****Rpg?*****) all co-segregate with each other in the Q21861/SM89010 population and are located in bin 13 of**
**Chromosome 7(5H)**

- DAK133

- Ltp1

- WG530

- ABC302

- BCD926

- ABG473

- MWG514B

- WG908

- ABG390

- ABG463

- ABG705A

- ABG395

- ABC324

- ABG496

- 1

- 2

- 3

- 4

- 5

- 6

- 7

- 8

- 9

- 10

- 11

- 12

- 13

- 14

- 15

***rpg4, Rpg5***

**Chromosome 7(5H) of Barley**

## Screening Recombinants in the rpg4/Rpg5 Region

**Screening Recombinants in the***** rpg4/Rpg5***** Region**

## Genetic and Physical Map of the rpg4/Rpg5 Region

**Genetic and Physical Map of the***** rpg4/Rpg5***** Region**

##  Summary

- In addition to wheat, barley is threatened by race TTKS worldwide
- Fortunately, resistance has been identified in cultivated, Swiss landrace, and wild barley
- Q2861 possesses a high level of resistance to race TTKS
- This resistance is conferred by a single gene that cosegregates with QCC and rye stem rust resistance in bin 13 of chromosome 7(5H)
- Research underway to whether TTKS resistance is conferred by *Rpg5* or another nearby R gene candidate

## 
Stephanie Dahl
Tamas Szinyei
USDA-NRI

- Stephanie Dahl
- Tamas Szinyei
- USDA-NRI

**Acknowledgements**

## Slide 20