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

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.

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

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  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 University of Minnesota, St. Paul Washington State University, Pullman

  2. Race TTKS • 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

  3. Race TTKS and Barley • 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

  4. Race TTKS and Midwest 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

  5. Evaluation of Hordeum to Race TTKS • 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

  6. Race TTKS Resistance Cultivated Germplasm Barley CAP Germplasm: 960 Accessions from 10 Different Programs

  7. Race TTKS Resistance Swiss Landraces 74 Accessions

  8. Race TTKS Resistance Wild Barley 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. Barley Line Q21861 • 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

  11. 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

  12. Barley Line Q21861 Reaction to Race TTKS • 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

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

  14. Q21861/SM89010 Reaction to Race TTKS

  15. Chromosome 7(5H) of Barley DAK133 1 MWG920.1A 2 ABG705A 3 ABG395 4 Ltp1 5 WG530 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) 6 ABC324 7 ABC302 8 BCD926 9 ABG473 10 MWG514B 11 WG908 12 ABG496 rpg4, Rpg5 13 ABG390 14 ABG463 15

  16. Screening Recombinants in the rpg4/Rpg5 Region

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

  18. 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. Acknowledgements Stephanie Dahl Tamas Szinyei USDA-NRI

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