Oat Crown Rust Disease Resistance: Two Sides to the Story

Plant disease, and therefore, susceptibility occurs when plants fail to recognize a pathogen. In addition to the failure of the plant immune system, there are other host processes that contribute to successful colonization by pathogens. Thus, advancing our understanding of the plant pathogen interactions is essential to control disease and invigorate crop breeding programs. Global oat production is severely affected by the pathogenic fungus Puccinia coronata f. sp. avenae (Pca), which causes oat crown rust disease. Because disease resistance is mediated by the recognition of pathogen effectors via plant immune receptors, we are aiming to discover both effectors and plant resistance genes to elucidate the molecular and genetic basis of virulence in Pca. Given the lack of genomic resources to study Pca pathogenicity, we generated de novo genome assemblies of two Pca isolates with contrasting virulence phenotypes. Genome annotation was carried out using gene expression data from various Pca developmental stages and computational predictions will be employed to catalog the effector repertoire of Pca. In a complementary approach, we are evaluating oat germplasm to find novel sources of oat crown rust resistance. Brachypodium distachyon, acts as a near-host for Pca, and thus we are using a diverse panel of Brachypodium genotypes to identify plant immunity mechanisms that may be effective against oat crown rust. Genetic loss of host susceptibility could be exploited as a novel source for disease resistance engineering, therefore we are utilizing transcriptomics data from oat and Brachypodium to determine key events leading to susceptibility or resistance.

Vahid Omidvar¹, Marisa Miller², Ying Zhang¹, Castle Raley³, Susan Rottshaefer¹, Feng Li¹, Benjamin Schwessinger⁴, John Rathjen⁴, Robert F. Park⁴, Cory D. Hirsch¹, Peter N. Dodds ^1,6, Shahryar F. Kianian^1,2, Melania Figueroa¹

¹University of Minnesota, Saint Paul, MN, USA

²USDA-ARS Cereal Disease Laboratory, Saint Paul, MN, USA

³Frederick National Laboratory for Cancer Research, Leidos Biomedical Research, Frederick, MD

⁴Australian National University, Canberra, ACT, Australia

⁵University of Sydney, Cobbitty, NSW, Australia

⁶CSIRO Agriculture and Food, Canberra, ACT, Australia