1. 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 Robert Brueggeman and Andris Kleinhofs University of Minnesota, St. Paul Washington State University, Pullman

2.  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 Race TTKS

3.  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 act as an early inoculum source for wheat for wheat  Barley is a significant food crop in many of the same areas where many of the same areas where wheat is threatened: ETH & ERI wheat is threatened: ETH & ERI Race TTKS and Barley

4.  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 Race TTKS and Midwest Barley

5.  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 Evaluation of Hordeum to Race TTKS

6. Race TTKS Resistance Cultivated Germplasm General Class #% Resistant0-160.0-16.7 Mod. Resist 2-13 2-13 2.0-13.5 2.0-13.5 Mod. Suscept 14-26 14-2614.6-27.1 Susceptible12-6512.5-67.7 Barley CAP Germplasm: 960 Accessions from 10 Different Programs

7. Race TTKS Resistance Swiss Landraces General Class #% Resistant5777.0 Mod. Resist 7 9.5 9.5 Mod. Suscept 00 Susceptible1013.5 74 Accessions

8. Race TTKS Resistance Wild Barley General Class #% Resistant525.0 Intermediate315.0 SusceptibleVariable7535.025.0 20 Accessions Resistant accessions from Israel, W. Tajikistan and E. Uzbekistan

9. 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

10.  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 Barley Line Q21861

11.  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 Barley Line Q21861

12.  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 Barley Line Q21861 Reaction to Race TTKS

13. Q21861 and SM89010 Parents Reaction to Race TTKS Q28161 SM89010

14. Q21861/SM89010 Reaction to Race TTKS RaceResistSusceptRatio X2X2X2X2 Prob>X 2 QCCJ56691:11.350.24 TTKS56691:11.350.24

15. 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

16. Screening Recombinants in the rpg4/Rpg5 Region

17. Genetic and Physical Map of the rpg4/Rpg5 Region

18. Summary 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

19. Stephanie Dahl Tamas Szinyei USDA-NRI Acknowledgements