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United States Department of Agriculture

Agricultural Research Service

Research Project: CHARACTERIZATION OF HOST-PATHOGEN INTERACTIONS IN BARLEY AND WHEAT

Location: Cereal Crops Research

Title: Host-selective toxins produced by Stagonospora nodorum confer disease susceptibility in adult wheat plants under field conditions

Authors
item FRIESEN, TIMOTHY
item Chu, C - NORTH DAKOTA STATE UNIV.
item Liu, Z - NORTH DAKOTA STATE UNIV.
item XU, STEVEN
item Halley, S - NORTH DAKOTA STATE UNIV.
item FARIS, JUSTIN

Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 13, 2009
Publication Date: March 6, 2009
Citation: Friesen, T.L., Chu, C.G., Liu, Z.H., Xu, S.S., Halley, S., Faris, J.D. 2009. Host-selective toxins produced by Stagonospora nodorum confer disease susceptibility in adult wheat plants under field conditions. Theoretical and Applied Genetics. 118:1489-1497

Interpretive Summary: Stagonospora nodorum blotch (SNB) caused by Stagonospora nodorum is a devastating pathogen of wheat worldwide. As is true for many necrotrophic diseases, SNB is complex and resistance to SNB is usually quantitatively inherited. We recently showed that S. nodorum produces at least four proteinaceous host-selective toxins that are important in SNB disease. Here, we evaluated a wheat population that segregates for sensitivity to the toxins SnToxA, SnTox2, and SnTox3 to determine toxin interactions are associated with adult plant susceptibility to SNB foliar disease under field conditions. Artificial inoculation indicated that compatible SnToxA and SnTox2 interactions accounted for as much as 18% of the variation in disease severity. Additional adult plant resistance QTLs were identified. Therefore, in this population, largely the same QTLs are responsible for seedling and adult plant resistance/susceptibility. This is the first report showing that host-selective toxins confer susceptibility of adult plants to SNB, further substantiating the importance of compatible toxin-host interactions in SNB.

Technical Abstract: Stagonospora nodorum, causal agent of Stagonospora nodorum blotch (SNB), is a devastating pathogen of wheat worldwide. As is true for many necrotrophic host-pathogen systems, the wheat-S. nodorum system is complex and resistance to SNB is usually quantitatively inherited. We recently showed that S. nodorum produces at least four proteinaceous host-selective toxins that interact with dominant host sensitivity/susceptibility gene products to induce SNB in seedlings. Here, we evaluated a population of wheat recombinant inbred lines that segregates for Tsn1, Snn2, and Snn3, which confer sensitivity to the toxins SnToxA, SnTox2, and SnTox3, respectively, to determine if compatible host-toxin interactions are associated with adult plant susceptibility to SNB foliar disease under field conditions. Artificial inoculation of the population in two years and two locations with a fungal isolate known to produce SnToxA and SnTox2 indicated that compatible SnToxA-Tsn1 and SnTox2-Snn2 interactions accounted for as much as 18 and 15% of the variation in disease severity on the flag leaf, respectively. As previously reported for seedlings, the effects of these two interactions in conferring adult plant susceptibility were largely additive. Additional adult plant resistance QTLs were identified on chromosomes 1B, 4B, and 5A, of which, the 1B and 5A QTLs were previously reported to be associated with seedling resistance to SNB. Therefore, in this population, largely the same QTLs are responsible for seedling and adult plant resistance/susceptibility. This is the first report showing that host-selective toxins confer susceptibility of adult plants to SNB, further substantiating the importance of compatible toxin-host interactions in the wheat-S. nodorum pathosystem.

Last Modified: 7/28/2014
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