Fine Mapping of the Wheat Leaf Rust Resistance Gene Lr16

Lr16 is a widely deployed leaf rust resistance gene that is effective against the North American Puccinia triticina population when in combination with Lr34.  Lr16 is a seedling leaf rust resistance gene conditioning an incompatible interaction with a distinct necrotic ring surrounding the pustule. Previously sequenced seedling leaf rust resistance genes (e.g Lr1, Lr10 and Lr21) were Resistance Gene Analog (RGA)-like genes. Lr16 has been mapped to the telomeric region of wheat chromosome bin 2BS3. We used two populations to fine map Lr16: an F₆‐derived recombinant inbred line (RIL) population consisting of 1872 lines from the cross between Canadian wheat lines BW278 and “AC Foremost” and  a Doubled Haploid (DH) population with 957 lines from the cross between wheat varieties “AC Majestic” and “Glenlea”. The gene was localized to 1.5cM and 3.4cM intervals in BW278/AC foremost and AC Majestic/Glenlea populations respectively. To better delineate the Lr16 interval, single nucleotide polymorphism (SNP) markers were developed from publicly available SNP databases and the wheat survey sequence. All identified SNPs were converted to Kompetitive Allele Specific PCR (KASP) assay markers. Here, we identified five RGA-like genes co-segregating with Lr16 in the RIL population and three of them were consistent in both populations. Moreover, the RGAs are orthologous to physically small region in Brachypodium and rice genomes respectively. We also identified ethyl methane sulfonate (EMS) induced mutants in the varieties “AC Domain” and “Kenyon” that have lost Lr16 function. Further analysis is pursued to validate Lr16 resistance gene using the mutants.