Dissecting the Genomic Architecture of Puccinia graminis f. sp. tritici - Wheat Interaction

Wheat stem rust caused by Puccinia graminis f. sp. tritici (Pgt) can lead to severe yield losses in wheat. The identification of genetic factors in wheat (R genes) and Pgt (avirulence genes) that define the outcome of infection (resistance vs. susceptibility) is critical for developing crops with long lasting resistance. In this project, we performed large-scale profiling of the virulence of 125 Pgt isolates (including the Ug99 race group) on a panel of 460 genetically and geographically diverse wheat accessions. A total of 57,500 disease resistance scores were collected and used to cluster wheat lines and Pgt isolates to investigate the geographic distribution of resistance and virulence in the host and pathogen populations, respectively. Strong geographically structured patterns of wheat resistance and Pgt virulence were detected. Genome-wide association mapping (GWAS) in the panel of wheat lines was performed to identify genomic regions harboring genes conferring resistance against each of the 125 Pgt isolates. The developed map of resistance loci revealed a complex genetic architecture and evolutionary dynamic of resistance against wheat stem rust. The distribution of GWAS signals showed a strong correlation with the distribution of NBS-LRR gene clusters, suggesting their importance in the origin of new resistance specificities. To understand the genetic basis of Pgt virulence, we are sequencing all the phenotyped Pgt isolates. A searchable database was constructed to facilitate public access to the project data (http://wheatgenomics.plantpath.ksu.edu/rustgenomics/).