The wild emmer wheat (Triticum turgidum ssp. dicoccoides; WEW) yellow (stripe) rust resistance genes Yr15, YrG303 and YrH52 were discovered in natural populations from different geographic locations. They all localize to chromosome 1B but were thought to be non-allelic based on differences in resistance response. We recently cloned Yr15 as a Wheat Tandem Kinase 1 (WTK1) and showed that these three resistance loci co-segregate in fine-mapping populations and share identical full-length genomic sequence of functional Wtk1. Independent EMS mutagenized susceptible yrG303 and yrH52 lines carried single nucleotide mutations in Wtk1 that disrupted function. A comparison of the mutations for yr15, yrG303 and yrH52 mutants showed that while key conserved residues were intact, other conserved regions in critical kinase subdomains were frequently affected demonstrating their importance for functionality. Introgression of Wtk1 into multiple genetic backgrounds resulted in variable phenotypic responses, confirming that Wtk1-mediated resistance is part of a complex immune response network. This information will be useful for future work on the possible molecular mechanism of Wtk1 and its role in plant innate immunity. The Wtk1-mediated resistance network is diverse in WEW natural populations subjected to natural selection and adaptation, confirming that WEW natural populations have potential to serve as a good source for evolutionary studies of different traits and multifaceted gene networks.
