|BERTUCCI, MATT - North Carolina State University|
|MURPHY, PAUL - North Carolina State University|
Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/22/2013
Publication Date: 3/10/2014
Citation: Bertucci, M., Brown Guedira, G.L., Murphy, P., Cowger, C. 2014. Genes conferring sensitivity to stagonospora nodorum necrotrophic effectors in stagonospora nodorum blotch-susceptible U.S. wheat cultivars. Plant Disease. 98:746-753.
Interpretive Summary: Stagonospora nodorum is a fungal pathogen that causes Stagonospora nodorum blotch (SNB), a yield- and quality-reducing disease of wheat. S. nodorum produces small molecules called necrotrophic effectors (NEs) that interact with matching sensitivity genes in wheat. This interaction can increase disease susceptibility in wheat. We investigated which wheat genes are causing sensitivity to the NEs of the southeastern U.S. S. nodorum population. We used a set of 25 winter wheat cultivars, many from the southeastern U.S. Almost all were susceptible to SNB. Thirty-three isolates of S. nodorum that had been collected from seven southeastern U.S states were used in the experiment. We grew those fungal isolates and obtained filtrates from them that were infiltrated into the leaves of the wheat seedlings. We also used control strains of a yeast, Pichia pastoris, that produced one of several NEs. The wheat seedlings’ reactions were classified as sensitive or insensitive. All SNB-susceptible cultivars were sensitive to at least one NE. Among the sensitive cultivars, 32% contained a sensitivity gene calledTsn1, and 64% contained the sensitivity gene Snn3. Also, 10 molecular markers were tested to see if they could reliably detect the presence of the sensitivity genes Tsn1, Snn1, Snn2, and Snn3 in wheat. Only one marker, Xfcp623, was reliable in the cultivars we assayed, and it proved capable of detecting the sensitivity gene Tsn1. Our results show which NE sensitivity genes may be making southeastern U.S. wheats more susceptible to SNB, and will help us breed for resistance to this widespread disease.
Technical Abstract: Stagonospora nodorum is a necrotrophic fungal pathogen that causes Stagonospora nodorum blotch (SNB), a yield- and quality-reducing disease of wheat. S. nodorum produces a set of necrotrophic effectors (NEs) that interact with the products of host sensitivity genes to cause cell death and increased susceptibility to disease. The focus of this study was determination of NE sensitivity among 25 winter wheat cultivars, many of them from the southeastern U.S., that are susceptible to SNB, as well as the moderately resistant cultivar NC-Neuse. Thirty-three isolates of S. nodorum that had been collected from seven southeastern U.S states were cultured for NE production and the filtrates were used in an infiltration bioassay. Control strains of Pichia pastoris that expressed SnToxA, SnTox1, or SnTox3, were also used. All SNB-susceptible cultivars were sensitive to at least one NE, while NC-Neuse was insensitive to all NEs tested. Among the sensitive lines, 32% contained sensitivity gene Tsn1 and 64% contained sensitivity gene Snn3. None were sensitive to SnTox1. Additionally, 10 molecular markers for sensitivity genes Tsn1, Snn1, Snn2, and Snn3 were evaluated for diagnostic potential. Only the marker Xfcp623 for Tsn1 was diagnostic, and it was in perfect agreement with the results of the infiltration bioassays. The results illuminate which NE sensitivity genes may be of concern in breeding for resistance to SNB in the southeastern U.S.