|BERTUCCI, MATT - North Carolina State University|
|MURPHY, J - North Carolina State University|
Submitted to: Eastern Wheat Workers and Southern Small Grain Workers Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 3/25/2013
Publication Date: N/A
Interpretive Summary: Stagonospora nodorum is a fungal pathogen that causes Stagonospora nodorum blotch (SNB), a yield- and quality-reducing disease of wheat that can cause major problems for wheat growers in the southeastern United States. Severe epidemics can result in yield losses of up to 50% in susceptible varieties. S. nodorum uses host-selective toxins, a set of small molecules that interact with certain sensitivity genes in the host. This leads to increased susceptibility in the field. This study was carried out to identify the sensitivity genes present in southeastern wheat lines that are highly susceptible to SNB. We also wanted to evaluate certain molecular markers for these sensitivity genes so that we could “breed them out.” None of the lines appeared to have the sensitivity gene Snn1. We found that 30% of the wheat lines we tested had the sensitivity gene Tsn1, and 62% had the sensitivity gene Snn3, suggesting the latter may be common in southeastern U.S. wheats. We found one molecular marker, Xfcp623, to be reliable in identifying wheat cultivars with Tsn1.
Technical Abstract: Stagonospora nodorum (teleomorph Phaeosphaeria nodorum) is a fungal pathogen that causes Stagonospora nodorum blotch (SNB), a yield- and quality-reducing disease of wheat that can cause major problems for wheat growers in the southeastern United States. Severe epidemics can result in yield losses of up to 50% in susceptible varieties. S. nodorum utilizes a set of necrotrophic effectors (NEs), also known as host-selective toxins, that contribute to disease severity. The NEs are proteins that interact with the host in an inverse gene-for-gene manner: sensitivity genes in the host recognize the effectors produced by the fungus and ultimately lead to increased susceptibility in the field. To date, there are six reported NEs in the wheat-S. nodorum pathosystem. The six NEs are recognized by seven sensitivity genes. The objectives of this study were to: identify the sensitivity genes present in southeastern wheat cultivars that are highly susceptible to SNB; and evaluate the diagnostic potential of molecular markers for these regionally important sensitivity genes, to aid in “breeding them out.” In summary, it was found that: 8 (30%) of the selected cultivars were sensitive to SnToxA and harbor Tsn; 16 (62%) of the selected cultivars were sensitive to SnTox3 and are presumed to harbor Snn3. This gene is widespread in eastern-U.S. wheat germplasm and screening against it appears to be important; and none of the cultivars were sensitive to SnTox1. Xfcp623 was found to be a diagnostic marker in the germplasm tested, and will be useful in screening out cultivars with SNB susceptibility conferred by Tsn1.