Resistance to Stem Rust Race TTKS Resistance to Stem Rust Race TTKS

Maps to the Maps to the rpg5rpg5//Rpg5Rpg5 Complex of Complex of

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

Brian Steffenson, Yue Jin,Brian Steffenson, Yue Jin, Robert Brueggeman and Andris KleinhofsRobert Brueggeman and Andris Kleinhofs

University of Minnesota, St. PaulUniversity of Minnesota, St. PaulWashington State University, PullmanWashington State University, Pullman

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

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

This race is a threat to global food securityThis race is a threat to global food security

Race TTKSRace TTKS

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

Susceptible to race TTKSSusceptible to race TTKS

With its early maturity, barley may With its early maturity, barley may act as an early inoculum source act as an early inoculum source for wheatfor wheat

Barley is a significant food crop inBarley is a significant food crop in many of the same areas wheremany of the same areas where wheat is threatened: ETH & ERI wheat is threatened: ETH & ERI

Race TTKS and BarleyRace TTKS and Barley

All of the Upper Midwest barley cultivars have All of the Upper Midwest barley cultivars have been bred with been bred with Rpg1Rpg1

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

But…But…Rpg1Rpg1 is ineffective against race TTKS is ineffective against race TTKS

Race TTKS and Midwest BarleyRace TTKS and Midwest Barley

Various Various HordeumHordeum accessions were assessed accessions were assessed for their reaction to race TTKS in the for their reaction to race TTKS in the greenhousegreenhouse

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

Evaluation of Evaluation of HordeumHordeum to Race TTKS to Race TTKS

Race TTKS Resistance Race TTKS Resistance Cultivated GermplasmCultivated Germplasm

General ClassGeneral Class ## %%

ResistantResistant 0-160-16 0.0-16.70.0-16.7

Mod. ResistMod. Resist 2-132-13 2.0-13.52.0-13.5

Mod. SusceptMod. Suscept 14-2614-26 14.6-27.114.6-27.1

SusceptibleSusceptible 12-6512-65 12.5-67.712.5-67.7

Barley CAP Germplasm: 960 Accessions from 10 Different Programs

Race TTKS Resistance Race TTKS Resistance Swiss LandracesSwiss Landraces

General ClassGeneral Class ## %%

ResistantResistant 5757 77.077.0

Mod. ResistMod. Resist 77 9.59.5

Mod. SusceptMod. Suscept 00 00

SusceptibleSusceptible 1010 13.513.5

74 Accessions

Race TTKS Resistance Race TTKS Resistance Wild BarleyWild Barley

General ClassGeneral Class ## %%

ResistantResistant 55 25.025.0

Intermediate Intermediate 33 15.015.0

SusceptibleSusceptible

Variable Variable

77

55

35.035.0

25.025.0

20 Accessions

Resistant accessions from Israel, W. Tajikistan andE. Uzbekistan

Vulnerability of Barley Vulnerability of Barley Stem RustStem Rust

Vulnerability of Barley Vulnerability of Barley Stem RustStem Rust

Race QCC arose in Race QCC arose in 1989; carried virulence 1989; carried virulence for for Rpg1Rpg1

From over 18,000 From over 18,000 accessions evaluated, accessions evaluated, only a few exhibited a only a few exhibited a high level of adult high level of adult plant resistance to plant resistance to pathotype QCCpathotype QCC

CIMMYT/ICARDA derived line with unknown CIMMYT/ICARDA derived line with unknown pedigreepedigree

Selection made by Roger Boyd in MexicoSelection made by Roger Boyd in Mexico

Resistance first found to race QCC by Alan Resistance first found to race QCC by Alan RoelfsRoelfs

Inheritance studies made and a single Inheritance studies made and a single recessive gene, recessive gene, rpg4rpg4, was found to confer , was found to confer resistance to race QCCresistance to race QCC

Barley Line Q21861Barley Line Q21861

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

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

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

Barley Line Q21861Barley Line Q21861

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

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

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

Barley Line Q21861Barley Line Q21861Reaction to Race TTKSReaction to Race TTKS

Q21861 and SM89010 ParentsQ21861 and SM89010 ParentsReaction to Race TTKSReaction to Race TTKS

Q28161 SM89010

Q21861/SM89010Q21861/SM89010Reaction to Race TTKSReaction to Race TTKS

RaceRace ResistResist SusceptSuscept RatioRatio XX22 Prob>XProb>X22

QCCJQCCJ 5656 6969 1:11:1 1.351.35 0.240.24

TTKSTTKS 5656 6969 1:11:1 1.351.35 0.240.24

MWG920.1A

Resistance to race QCC (rpg4), ryestem 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 ofChromosome 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 theScreening Recombinants in the rpg4/Rpg5 rpg4/Rpg5 Region Region

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

SummarySummary SummarySummary

In addition to wheat, barley is threatened by race TTKS In addition to wheat, barley is threatened by race TTKS worldwideworldwide

Fortunately, resistance has been identified in cultivated, Swiss Fortunately, resistance has been identified in cultivated, Swiss landrace, and wild barleylandrace, and wild barley

Q2861 possesses a high level of resistance to race TTKSQ2861 possesses a high level of resistance to race TTKS

This resistance is conferred by a single gene that cosegregates This resistance is conferred by a single gene that cosegregates with QCC and rye stem rust resistance in bin 13 of with QCC and rye stem rust resistance in bin 13 of chromosome 7(5H)chromosome 7(5H)

Research underway to whether TTKS resistance is conferred Research underway to whether TTKS resistance is conferred by by Rpg5Rpg5 or another nearby R gene candidate or another nearby R gene candidate

Stephanie DahlStephanie Dahl

Tamas SzinyeiTamas Szinyei

USDA-NRIUSDA-NRI

AcknowledgementsAcknowledgements