ARS | Publication request: Brachypodium as a model for investigations of nonhost resistance to stem rust

Submitted to: American Society of Plant Biologists Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: July 20, 2012
Publication Date: July 20, 2012
Citation: Garvin, D.F. 2012. Brachypodium as a model for investigations of nonhost resistance to stem rust [abstract]. American Society of Plant Biologists Annual Meeting, Plant Biology 2012, July 20-24, 2012, Austin, Texas. Abstract No. P25039.

Technical Abstract: The model grass Brachypodium distachyon (Brachypodium), a relative of cool season grain crops, has emerged as a system for both structural and functional genomics research. Unlike Arabidopsis, Brachypodium is reported to be a host for rust diseases caused by the fungal genus Puccinia. Given the threat to global wheat production from new virulent races of P. graminis, the causal agent of stem rust, we are employing Brachypodium to explore stem rust resistance with a particular focus on refining our understanding of nonhost resistance. We have found genetic variation in Brachypodium for response to different formae speciales of P. graminis, including timothy stem rust and wheat stem rust, although complete susceptibility does not appear to be present and significant development of sporulating pustules is rare. Genetic analysis suggests that a single gene is largely responsible for the difference in timothy stem rust resistance between two contrasting genotypes, and we speculate that susceptibility is due to an alteration in a gene integral to nonhost resistance. Using high throughput sequencing, we rapidly mapped the putative location of this gene and efforts to isolate it are proceeding. Similarly we are employing mutagenesis to perturb genes associated with stem rust resistance in Brachypodium, and we have recovered mutants that exhibit both increased susceptibility and resistance to timothy stem rust, and putative wheat stem rust mutants have been recovered. By characterizing the molecular basis of both natural and induced variation for resistance to different stem rust f. sp., we hope to determine the breadth to which Brachypodium nonhost resistance genes function against P. graminis. This research will provide new knowledge on the complex nature of nonhost resistance and will have practical application in engineering durable stem rust resistance in wheat and other cool season cereal crops.