This document summarizes research mapping durable adult plant resistance to stem rust in wheat. Nine consistent and five inconsistent quantitative trait loci (QTLs) were detected across six mapping populations. A QTL on chromosome 3BS was found in all parents and is linked to resistance gene Sr2. A QTL on chromosome 7DS confirms the involvement of gene Lr34. A QTL on chromosome 1BL suggests the involvement of gene Lr46. These QTLs in combination with Sr2 form the "Sr2-Complex" conferring durable adult plant resistance. Future work will include fine mapping of QTLs and pyramiding adult plant resistance with major genes using markers.

1. Mapping of durable adult plant stem rust resistance to Ug99 and its races S. Bhavani, R. P. Singh, S. Singh, J. Huerta, O. Argillier, S. Brun, S. Lacam, N. Desmouceaux, P. Njau and R. Wanyera

3. Threat to significant proportion of global wheat germplasm > 80% susceptible

4. New races in Ug99 (TTKSK) lineageUg99+Sr24 Virulence (2006)-TTKST Ug99+Sr36 Virulence (2007)-TTTSK Other races-TTKSF,TTKSP, PTKSK, PTKST Virulence spectrum of Ug99 (TTKSK)

5. Types of Resistance ≈ Race-specific ≈ Major genes ≈ Hypersensitive Monogenic (Boom & Bust) Pyramiding ≈ Race-nonspecific ≈ Minor genes ≈ Slow rusting/ Partial Polygenic (Durable)

7. Mutating and migrating nature of rust pathogens

10. Lower disease severity, Increased latent period

11. Small to large compatible pustules on stems

14. Sr2 still provides moderate levels of resistance in Kenya (~30% reduction in disease severity)

15. Seedling and APR genes with intermediate effects in combination with Sr2 produce enhanced levels of resistance

17. Identifying materials with adult plant resistance to Ug99 Kingbird Greenhouse seedling tests -USDA-ARS Lab. in St. Paul, Minnesota, USA Field evaluations-Kenya/Ethiopia Characterization of PBC phenotype and Sr2 linked molecular markers Identified APR Sources: Kingbird, Kiritati, Juchi, Pavon, Huirivis#1, Muu, Kenya Swara, Kenya Kudu, Parula, Picaflor, Danphe, Chonte

19. Genetic studies suggest the involvement of 3 or 4 minor genes in each resistant parent

20. Initial molecular mapping of six populations completed

22. Artificial epidemics with Ug99+Sr24 (TTKST)

24. Inclusive Composite Interval Mapping (ICIM), Q-gene, QTL Cartographer

25. ICIM- http://www.isbreeding.net/

26. Increased power of detection

27. Additive and Epistatic Effects

28. LOD Scores>2.5, Probability in step wise regression 0.001

30. PBW343 X Kingbird 5B 1A 3BS 7AL 7DS PBC

31. PBW343 X Kiritati Kiritati PBW343

32. PBW343 X Kiritati 7DS 3BS 2D 5BS

33. PBW343 X Juchi Juchi PBW343

34. PBW343 X Juchi 2BS 3BS 4AS 5BL 6BS

35. Avocet X Pavon 76 (RILs without Sr26) Pavon 76

36. Avocet X Pavon 76 3BS 2BS 1BL 6BS 3D 5A

37. PBW343 X Huirivis#1 Huirvis#1 PBW343

38. PBW343 X Hurivis#1 3BS 2BS 5BL PBC 5D

39. PBW343 X MUU Muu PBW343

40. PBW343 X MUU 3BS 2BS 5BL

41. Inconsistent QTLs 4BS-Kingbird 2A-Kingbird 2D-Kiritati 5A-Pavon 5DS-Hurivis#1

43. QTL on chromosome 3BS in all parents is linked to resistance gene Sr2 & PBC

45. 7 new QTLs identified on chromosomes 1A, 2B, 3D, 4A, 5B, 6B and 7A

46. 5 inconsistent QTLs identified on chromosomes 2A, 2D, 4B, 5A and 5D

48. Development of PCR based assays for flanking markers

49. Pyramiding APR + major genes using markers

51. Grain Research and Development Corporation (GRDC), Australia

52. Kenya Agricultural Research InstituteTHANK YOU