Mapping and Characterization of a Wheat Stem Rust Resistance Gene in Durum Wheat Kronos

Wheat stem (or black) rust is one of the most devastating fungal diseases, threatening global wheat production. Identification, mapping, and deployment of effective resistance genes are critical to addressing this challenge. In this study, we mapped and characterized one stem rust resistance (Sr) gene from the tetraploid durum wheat variety Kronos (temporary designation SrKN). This gene was mapped on the long arm of chromosome 2B and confers resistance to multiple virulent Pgt races, such as TRTTF and BCCBC. Using a large mapping population (3,366 gametes), we mapped SrKN within a 0.29 cM region flanked by the sequenced-based markers pku4856F2R2 and pku4917F3R3, which corresponds to 5.6- and 7.2-Mb regions in the Svevo and Chinese Spring reference genomes, respectively. Both regions include a cluster of nucleotide binding leucine-repeat (NLR) genes that likely includes the candidate gene. An allelism test failed to detect recombination between SrKN and the previously mapped Sr9e gene. This result, together with the similar seedling resistance responses and resistance profiles, suggested that SrKN and Sr9e may represent the same gene. We introgressed SrKN into common wheat and developed completely linked markers to accelerate its deployment in the wheat breeding programs. SrKN can be a valuable component of transgenic cassettes or gene pyramids that includes multiple resistance genes to control this devastating disease.

Automated summary

In this study, a stem rust resistance gene SrKN was mapped and characterized from the durum wheat variety Kronos. The gene confers resistance to multiple virulent Pgt races and was mapped to chromosome 2B. Through a large mapping population, SrKN was located within a 0.29 cM region containing nucleotide binding leucine-repeat (NLR) genes that may include the candidate gene. An allelism test suggested that SrKN and the previously mapped Sr9e gene may represent the same gene. SrKN was introgressed into common wheat and completely linked markers were developed for accelerated deployment in wheat breeding programs.