Exploring Leaf Rust Resistance in Aegilops tauschii using Association Genetics Coupled with Resistance Gene Capture

Leaf rust of wheat, caused by the obligate biotrophic pathogen Puccinia triticina, is the most common among the three rusts of wheat worldwide. Wheat leaf rust epidemics can cause significant yield losses, and the most economical and environmentally sound method to control them is breeding for resistance to this pathogen. There are more than 70 leaf rust resistance genes that have been mapped and designated in wheat, but the sequences of only a handful of genes have been identified so far. Many of these genes, including some of the cloned ones, have been transferred into cultivated wheat from the diploid wild wheat progenitor Aegilops tauschii. Access to the sequences of such resistance genes benefit breeders by allowing them to design gene-specific markers to quickly and cheaply track them in their breeding programs. It also helps researchers understand the genetic architecture of leaf rust resistance, and how it can be engineered to stay one step ahead of a rapidly evolving pathogen. Traditional map-based or mutational genomics-based gene cloning approaches are time and labour intensive, as they involve creating structured populations. A novel method for resistance gene cloning, which combines association genetics with resistance gene enrichment sequencing (AgRenSeq), can be used instead to rapidly obtain candidate genes for resistance in a diversity panel of wild wheat. Here, it will be described how AgRenSeq has been used to identify candidate genes for leaf rust resistance on chromosomes 1D and 2D using an Aegilops tauschii panel. Furthermore, it will be discussed how this data has been used to explore the candidate genes’ frequencies in the panel to dissect the genetic architecture of leaf rust resistance against several races from North America and Europe.