title: Characterization of Brachypodium distachyon as a nonhost model against switchgrass rust pathogen Puccinia emaculata.
abstract: BACKGROUND
  Switchgrass rust, caused by Puccinia emaculata, is an important disease of switchgrass, a potential biofuel crop in the United States. In severe cases, switchgrass rust has the potential to significantly affect biomass yield. In an effort to identify novel sources of resistance against switchgrass rust, we explored nonhost resistance against P. emaculata by characterizing its interactions with six monocot nonhost plant species. We also studied the genetic variations for resistance among Brachypodium inbred accessions and the involvement of various defense pathways in nonhost resistance of Brachypodium.
  
  
  RESULTS
  We characterized P. emaculata interactions with six monocot nonhost species and identified Brachypodium distachyon (Bd21) as a suitable nonhost model to study switchgrass rust. Interestingly, screening of Brachypodium accessions identified natural variations in resistance to switchgrass rust. Brachypodium inbred accessions Bd3-1 and Bd30-1 were identified as most and least resistant to switchgrass rust, respectively, when compared to tested accessions. Transcript profiling of defense-related genes indicated that the genes which were induced in Bd21after P. emaculata inoculation also had higher basal transcript abundance in Bd3-1 when compared to Bd30-1 and Bd21 indicating their potential involvement in nonhost resistance against switchgrass rust.
  
  
  CONCLUSIONS
  In the present study, we identified Brachypodium as a suitable nonhost model to study switchgrass rust which exhibit type I nonhost resistance. Variations in resistance response were also observed among tested Brachypodium accessions. Brachypodium nonhost resistance against P. emaculata may involve various defense pathways as indicated by transcript profiling of defense related genes. Overall, this study provides a new avenue to utilize novel sources of nonhost resistance in Brachypodium against switchgrass rust.
authors.affiliation: Plant Biology Division, The Samuel Roberts Noble Foundation, Ardmore, Oklahoma, 73401, USA. ugill@noble.org.
authors.forename: Upinder S
authors.initials: US
authors.lastname: Gill
authors.affiliation: Plant Biology Division, The Samuel Roberts Noble Foundation, Ardmore, Oklahoma, 73401, USA. srinivasaraou@yahoo.com.|Current address: Biologicals and Fungicide Discovery, DuPont Crop Protection, Newark, DE 19711, USA. srinivasaraou@yahoo.com.
authors.forename: Srinivasa R
authors.initials: SR
authors.lastname: Uppalapati
authors.affiliation: Plant Biology Division, The Samuel Roberts Noble Foundation, Ardmore, Oklahoma, 73401, USA. jnakashima@noble.org.
authors.forename: Jin
authors.initials: J
authors.lastname: Nakashima
authors.affiliation: Plant Biology Division, The Samuel Roberts Noble Foundation, Ardmore, Oklahoma, 73401, USA. ksmysore@noble.org.
authors.forename: Kirankumar S
authors.initials: KS
authors.lastname: Mysore
mesh_terms: D001487:Basidiomycota / Q000235:genetics / Q000472:pathogenicity*; D058431:Brachypodium / Q000382:microbiology*; D020869:Gene Expression Profiling; D005800:Genes, Fungal; D008954:Models, Biological; D012333:RNA, Messenger / Q000235:genetics
chemical_list: D012333:RNA, Messenger