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United States Department of Agriculture

Agricultural Research Service

Research Project: IMPROVEMENT OF HARD RED SPRING AND DURUM WHEAT FOR DISEASE RESISTANCE AND QUALITY USING GENETICS AND GENOMICS Title: Re-Evaluation of a Tetraploid Wheat Population Indicates That the Tsn1-ToxA Interaction is the Only Factor Governing Stagonospora Nodorum Blotch Susceptibility

Authors
item Faris, Justin
item Friesen, Timothy

Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 7, 2009
Publication Date: August 1, 2009
Citation: Faris, J.D., Friesen, T.L. 2009. Re-Evaluation of a Tetraploid Wheat Population Indicates That the Tsn1-ToxA Interaction is the Only Factor Governing Stagonospora Nodorum Blotch Susceptibility. Phytopathology. 99:(8) 906-912

Interpretive Summary: The wheat Tsn1 gene confers sensitivity to the host-selective toxin ToxA produced by the pathogens that cause tan spot and Stagonospora nodorum blotch (SNB), two foliar diseases of wheat. The Tsn1 gene is known to play a major role in conferring susceptibility of common (bread) wheat to SNB. However, a recent study suggested that Tsn1 was not relevant in conferring susceptibility of the durum wheat cultivar Langdon (LDN). Here, we re-evaluated the role of the Tsn1 in governing SNB susceptibility using the same durum genetic materials and pathogen isolate as were used in the previous study. Our results proved unequivocally that Tsn1 is the only factor present in these LDN-derived materials that governs response to SNB and that a compatible Tsn1-ToxA interaction is necessary for the manifestation of disease. Therefore, the results from the previous study are refuted.

Technical Abstract: The wheat Tsn1 gene on chromosome 5B confers sensitivity to the host-selective toxin ToxA produced by the pathogens that cause tan spot and Stagonospora nodorum blotch (SNB). A compatible Tsn1-ToxA interaction is known to play a major role in conferring susceptibility of hexaploid (common) wheat to SNB. However, a recent study suggested that the Tsn1-ToxA interaction was not relevant in conferring susceptibility of the tetraploid (durum) wheat cultivar Langdon (LDN). Here, we re-evaluated the role of the Tsn1-ToxA interaction in governing SNB susceptibility using the same mapping population and Stagonospora nodorum isolate (Sn2000) as were used in the previous study. Results of our QTL analysis showed that the Tsn1 locus accounted for 95% of the variation in SNB. In addition, inoculation of the mapping population with two ToxA-knockout strains of Sn2000 revealed that the entire population was resistant. Furthermore, several LDN Tsn1-disrupted mutants were evaluated and found to be resistant to SNB. Together, these results prove unequivocally that Tsn1 is the only factor present along chromosome 5B that governs response to SNB in this population and that a compatible Tsn1-ToxA interaction is necessary for the manifestation of disease. Therefore, the results from the previous study are refuted.

Last Modified: 12/17/2014