The Interaction of the Wheat Multi-Pest Resistance Gene Lr67 with other Leaf Rust Resistance Genes

The wheat leaf rust resistance gene Lr67 also confers resistance to stripe rust and stem rust. It is similar in this respect to another multi-pest resistance gene in wheat Lr34. Both genes have been cloned and code for different types of cellular transporters. With combinations of most leaf rust resistance genes the infection phenotype observed is similar to the most effective of the genes involved. However, Lr34 is known to interact with other leaf rust resistance genes in an additive manner, and combinations of genes involving Lr34 are more resistant than any of the genes involved. To investigate if this could also be the case for Lr67 we developed doubled haploid populations of the crosses Lr34/Lr13, Lr34/Lr16, Lr34/Lr32, Lr67/Lr13, Lr34/Lr16, and Lr34/Lr32 in otherwise susceptible genetic backgrounds. Progeny from these crosses were field tested over four years to determine the resistance level of lines containing either gene alone or lines with both genes. Lr34 interacted additively with Lr13, Lr16 and Lr32, in that the resistance of lines with both genes combined was better than lines with either gene alone. Lr67 interacted additively with Lr16 and Lr32 but not with Lr13. It appears that Lr67 does interact additively with at least some other leaf rust resistance genes, similar to Lr34.