ARS | Publication request: Two Homoeologous Wheat Genes Confer Sensitivity to a Single Host-Selective Toxin and Susceptibility to Stagonospora nodorum blotch (SNB)

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: November 12, 2009
Publication Date: January 9, 2010
Citation: Zhang, Z., Friesen, T.L., Shi, G., Rasmussen, J.B., Faris, J.D. 2010. Two Homoeologous Wheat Genes Confer Sensitivity to a Single Host-Selective Toxin and Susceptibility to Stagonospora nodorum blotch (SNB). Meeting Abstract. pg 188

Technical Abstract: The pathogen Stagonospora nodorum produces multiple host-selective toxins that interact with corresponding wheat sensitivity genes in an inverse gene-for-gene manner to cause the disease Stagonospora nodorum blotch (SNB) in wheat. Here, we screened accessions of Aegilops tauschii, the D-genome donor of common hexaploid wheat (Triticum aestivum), with culture filtrate derived from isolate Sn4. One sensitive and one insensitive accession were selected to develop an F2 population. Bulked-segregant analysis and molecular mapping indicated that the new toxin sensitivity gene, temporarily designated Snn5DS, mapped to chromosome arm 5DS. Spore inoculation of the population with isolate Sn4 indicated that all toxin-sensitive plants were susceptible and all toxin-insensitive plants were resistant. In related research, SnTox3, which interacts with the Snn3 gene on wheat chromosome arm 5BS, was isolated, and further evaluation of the F2 population indicated that the toxin interacting with Snn5DS was SnTox3. Comparative mapping revealed that Snn3 and Snn5DS are homoeologous and thus derived from a common ancestor. Further characterization indicated that, as opposed to most host-toxin interactions in the wheat-S. nodorum pathosystem, the Snn3/Snn5DS-SnTox3 interaction is not dependent on light, which suggests that a different host metabolic pathway is exploited to cause disease. Saturation and high-resolution mapping delineated the Snn5DS locus to a 1.4 cM interval, and analysis of colinearity indicated the Snn5DS region is well conserved between wheat, rice and Brachypodium, which will aid in the map-based cloning of Snn5DS.