title: Sr36- and Sr5-Mediated Resistance Response to Puccinia graminis f. sp. tritici Is Associated with Callose Deposition in Wheat Guard Cells.
abstract: Race-specific resistance of wheat to Puccinia graminis f. sp. tritici is primarily posthaustorial and often involves the induction of a hypersensitive response (HR). The aim of this study was to investigate host defense responses induced in interactions between P. graminis f. sp. tritici races and wheat lines carrying different race-specific stem rust resistance (Sr) genes. In incompatible interactions between wheat lines carrying Sr36 in three genetic backgrounds (LMPG, Prelude, or W2691) and avirulent P. graminis f. sp. tritici races MCCFC or RCCDM, callose accumulated within 24 h in wheat guard cells contacted by a P. graminis f. sp. tritici appressorium, and P. graminis f. sp. tritici ingress was inhibited following appressorium formation. Accordingly, the expression of transcripts encoding a callose synthase increased in the incompatible interaction between LMPG-Sr36 and avirulent P. graminis f. sp. tritici race MCCFC. Furthermore, the inhibition of callose synthesis through the infiltration of 2-deoxy-D-glucose (DDG) increased the ability of P. graminis f. sp. tritici race MCCFC to infect LMPG-Sr36. A similar induction of callose deposition in wheat guard cells was also observed within 24 h after inoculation (hai) with avirulent P. graminis f. sp. tritici race HKCJC on LMPG-Sr5 plants. In contrast, this defense response was not induced in incompatible interactions involving Sr6, Sr24, or Sr30. Instead, the induction of an HR and cellular lignification were noted. The manifestation of the HR and cellular lignification was induced earlier (24 hai) and was more extensive in the resistance response mediated by Sr6 compared with those mediated by Sr24 or Sr30. These results indicate that the resistance mediated by Sr36 is similar to that mediated by Sr5 but different from those triggered by Sr6, Sr24, or Sr30. Resistance responses mediated by Sr5 and Sr36 are prehaustorial, and are a result of very rapid recognition of molecules derived from avirulent isolates of P. graminis f. sp. tritici, in contrast to the responses triggered in lines with Sr6, Sr24, and Sr30.
authors.affiliation: First, second, and third authors: Cereal Research Centre, Agriculture and Agri-Food Canada, 101 Route 100, Morden, MB, R6M 1Y5, Canada; fourth author: Pacific Agri-Food Research Centre, Agriculture and Agri Food Canada, Summerland, BC, VOH 1ZO, Canada; and fifth author: Forensic Science Program, and Environmental and Life Sciences Graduate Program Trent University, Peterborough, ON, K9J 7B8, Canada.
authors.forename: X
authors.initials: X
authors.lastname: Wang
authors.affiliation: First, second, and third authors: Cereal Research Centre, Agriculture and Agri-Food Canada, 101 Route 100, Morden, MB, R6M 1Y5, Canada; fourth author: Pacific Agri-Food Research Centre, Agriculture and Agri Food Canada, Summerland, BC, VOH 1ZO, Canada; and fifth author: Forensic Science Program, and Environmental and Life Sciences Graduate Program Trent University, Peterborough, ON, K9J 7B8, Canada.
authors.forename: B D
authors.initials: BD
authors.lastname: McCallum
authors.affiliation: First, second, and third authors: Cereal Research Centre, Agriculture and Agri-Food Canada, 101 Route 100, Morden, MB, R6M 1Y5, Canada; fourth author: Pacific Agri-Food Research Centre, Agriculture and Agri Food Canada, Summerland, BC, VOH 1ZO, Canada; and fifth author: Forensic Science Program, and Environmental and Life Sciences Graduate Program Trent University, Peterborough, ON, K9J 7B8, Canada.
authors.forename: T
authors.initials: T
authors.lastname: Fetch
authors.affiliation: First, second, and third authors: Cereal Research Centre, Agriculture and Agri-Food Canada, 101 Route 100, Morden, MB, R6M 1Y5, Canada; fourth author: Pacific Agri-Food Research Centre, Agriculture and Agri Food Canada, Summerland, BC, VOH 1ZO, Canada; and fifth author: Forensic Science Program, and Environmental and Life Sciences Graduate Program Trent University, Peterborough, ON, K9J 7B8, Canada.
authors.forename: G
authors.initials: G
authors.lastname: Bakkeren
authors.affiliation: First, second, and third authors: Cereal Research Centre, Agriculture and Agri-Food Canada, 101 Route 100, Morden, MB, R6M 1Y5, Canada; fourth author: Pacific Agri-Food Research Centre, Agriculture and Agri Food Canada, Summerland, BC, VOH 1ZO, Canada; and fifth author: Forensic Science Program, and Environmental and Life Sciences Graduate Program Trent University, Peterborough, ON, K9J 7B8, Canada.
authors.forename: B J
authors.initials: BJ
authors.lastname: Saville
mesh_terms: D001487:Basidiomycota / Q000502:physiology*; D060467:Disease Resistance; D005838:Genotype; D005936:Glucans / Q000378:metabolism*; D010935:Plant Diseases / Q000276:immunology* / Q000382:microbiology; D010940:Plant Proteins / Q000235:genetics*; D018547:Plant Stems / Q000235:genetics / Q000276:immunology / Q000382:microbiology; D014908:Triticum / Q000235:genetics* / Q000276:immunology / Q000378:metabolism / Q000382:microbiology
chemical_list: D005936:Glucans; D010940:Plant Proteins; C048306:callose
keywords: wheat stem rust