Durable Leaf Rust Resistance in Wheat J. A. Kolmer USDA-ARS Cereal Disease Laboratory

Puccinia triticina - Wheat Leaf Rust Most common rust of wheat in U.S. Occurs nearly wherever wheat is grown Asexual in North America races in U.S. Annual yield losses

Leaf Rust Virulence Dynamics Kansas - Nebraska

U.S. Hard Red Spring Wheat  Wheaton (1983) Lr10, Lr23, Lr13, Lr34 +? Norm (1992) Lr1, Lr10, Lr13, Lr16, Lr23, Lr34 Norm (1992) Lr1, Lr10, Lr13, Lr16, Lr23, Lr34 both highly resistance since release both highly resistance since release  Alsen (2000) Lr2a, Lr10, Lr13, Lr23, Lr34 R-MR R-MR  Knudson (2002) Lr3, Lr10, Lr13, Lr16, Lr23, Lr34 Briggs (2002) Lr13, Lr16, Lr30, Lr34 Briggs (2002) Lr13, Lr16, Lr30, Lr34 Both highly resistant Both highly resistant  Marshall (1982) Lr2a, Lr10, Lr13, Lr34 Mod. Susceptible Mod. Susceptible

Effective Lr genes in spring wheat cvs. Alsen 2a,10, 13, 23, MR Norm 1, 10, 16, 23, 13, 34 Trace R Knudson 3, 10, 16, 23, 13, 34 Trace R TcLr MS TcLr R MR TcLr M Thatcher S Lr16, Lr23, Lr34 common in spring wheat

South American Landraces  Americano 25e (1918) Lr3, Lr16, LrX1,LrAPR  Americano 44d (1918) 1-2 APR genes THBJ Field THBJ Field  Tc*2/Am. 25e LrAPR ;2- 30 MRMS  Tc*2/Am.44d LrAPR ;23 20 M  Tc*2/Am.44d LrAPR ;2- 20 MRMS

U.S. Soft Red Winter Wheat Coker 9663 (1996) Lr9, Lr10, Lr14a Coker 9663 (1996) Lr9, Lr10, Lr14a R-MR R-MR Pioneer 26R61 (1999) Lr13, Lr14b, Lr26 Pioneer 26R61 (1999) Lr13, Lr14b, Lr26 R-MR R-MR

Lr34 in U.S. Wheat Hard red spring wheat Hard red spring wheat  Minnesota common 1966-mid 1990s common 1966-mid 1990s FHB resistant cvs. lack Lr34 FHB resistant cvs. lack Lr34  South Dakota - few cvs. with Lr34 few cvs. with Lr34  North Dakota - few cvs. with Lr34 few cvs. with Lr34 TcLr34 Tc

Lr34 in U.S. Wheat  Soft red winter wheat - old and new cvs. - not present - not present  Hard red winter wheat - very rare  Western spring wheat - not present TcLr34 Tc CSIRO PCR Marker Tip die back

Lr genes in U.S. Wheat Seedling resistance genes Seedling resistance genes - lower ploidy relatives - lower ploidy relatives - common wheat - common wheat Virulent races arise quickly Virulent races arise quickly Lr9, Lr16, Lr26 - still provide some resistance Lr9, Lr16, Lr26 - still provide some resistance Adult Plant Genes Adult Plant Genes Lr34 - not sufficient alone Lr34 - not sufficient alone Lr12 - ineffective Lr12 - ineffective Lr13 - ineffective Lr13 - ineffective Lr23 - characteristics of APR Lr23 - characteristics of APR  Combinations of Lr34 + effective seedling genes = best resistance = best resistance TcLr34 TcLr13 TcLr12 Tc