title: Identification and characterization of a novel host-toxin interaction in the wheat-Stagonospora nodorum pathosystem.
abstract: Stagonospora nodorum, casual agent of Stagonospora nodorum blotch (SNB) of wheat, produces a number of host-selective toxins (HSTs) known to be important in disease. To date, four HSTs and corresponding host sensitivity genes have been reported, and all four host-toxin interactions are significant factors in the development of disease. Here, we describe the identification and partial characterization of a fifth S. nodorum produced HST designated SnTox4. The toxin, estimated to be 10-30 kDa in size, was found to be proteinaceous in nature. Sensitivity to SnTox4 is governed by a single dominant gene, designated Snn4, which mapped to the short arm of wheat chromosome 1A in a recombinant inbred (RI) population. The compatible Snn4-SnTox4 interaction is light dependent and results in a mottled necrotic reaction, which is different from the severe necrosis that results from other host-toxin interactions in the wheat-S. nodorum pathosystem. QTL analysis in a population of 200 RI lines derived from the Swiss winter wheat varieties Arina and Forno revealed a major QTL for SNB susceptibility that coincided with the Snn4 locus. This QTL, designated QSnb.fcu-1A, explained 41.0% of the variation in disease on leaves of seedlings indicating that a compatible Snn4-SnTox4 interaction plays a major role in the development of SNB in this population. Additional minor QTL detected on the short arms of chromosomes 2A and 3A accounted for 5.4 and 6.0% of the variation, respectively. The effects of the three QTL were largely additive, and together they explained 50% of the total phenotypic variation. These results provide further evidence that host-toxin interactions in the wheat-S. nodorum pathosystem follow an inverse gene-for-gene model.
authors.affiliation: Department of Plant Sciences, North Dakota State University, Fargo, ND, 58105, USA.
authors.forename: Nilwala S
authors.initials: NS
authors.lastname: Abeysekara
authors.forename: Timothy L
authors.initials: TL
authors.lastname: Friesen
authors.forename: Beat
authors.initials: B
authors.lastname: Keller
authors.forename: Justin D
authors.initials: JD
authors.lastname: Faris
mesh_terms: D001203:Ascomycota / Q000737:chemistry / Q000472:pathogenicity; D002874:Chromosome Mapping; D032461:Chromosomes, Plant; D020224:Expressed Sequence Tags; D005819:Genetic Markers; D054884:Host-Pathogen Interactions; D010935:Plant Diseases / Q000382:microbiology*; D014118:Toxins, Biological / Q000378:metabolism*; D014908:Triticum / Q000235:genetics / Q000382:microbiology
chemical_list: D005819:Genetic Markers; D014118:Toxins, Biological