ARS | Publication request: Resistance to tan spot and insensitivity to Ptr ToxA in wheat

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 30, 2010
Publication Date: March 14, 2011
Repository URL: http://51: 3: 1059-1067
Citation: Noriel, A.J., Sun, X., Bockus, W., Bai, G. 2011. Resistance to tan spot and insensitivity to Ptr ToxA in wheat. Crop Science. 51:3:1059-1067.

Interpretive Summary: Tan spot is a wheat leaf disease caused by the fungus Pyrenophora tritici-repentis. Tan spot is an important disease that can significantly reduce wheat yields worldwide. Host-selective toxins produced by the fungus are responsible for leaf damage. Growing resistant cultivars is an effective approach to reduce the losses caused by the disease. To identify resistance genes in common wheat, 380 wheat accessions from different geographical origins were evaluated for resistance to P. tritici-repentis race 1, the predominant race in the Great Plains of U.S.A. and western Canada, and for insensitivity to Ptr ToxA, a toxin produced by race 1. About 60% of accessions tested were resistant and only 24% were as susceptible as the susceptible check. A total of 230 accessions showed insensitivity to Ptr ToxA, but only 158 of them also showed resistance to race 1. The results suggest that insensitivity to Ptr ToxA is not the only factor for resistance to race 1, other factors such as Ptr ToxC might also contribute to tan spot damage in some accessions. The tan spot resistant accessions identified in this study should be useful sources for developing new tan spot resistant cultivars.

Technical Abstract: Tan spot, caused by the fungus Pyrenophora tritici-repentis, is an important foliar disease of wheat worldwide. Growing resistant cultivars is an effective approach to reduce the losses caused by the disease. To identify resistance genes in common wheat, 380 wheat accessions from different geographical origins were evaluated for resistance to P. tritici-repentis race 1, the predominant race in the Great Plains of U.S.A. and western Canada, and insensitivity to Ptr ToxA, a host-selective toxin produced by race 1. Most accessions tested (60%) were resistant and only 93 accessions (24%) were as susceptible as TAM 105, the susceptible control. Among 380 accessions, 230 were insensitive to Ptr ToxA, but only 158 of them showed resistance to race 1. A weak correlation between tan spot score and sensitivity to Ptr ToxA suggests that pathogenicity factors other than Ptr ToxA (like Ptr ToxC) also contributed to tan spot development in these accessions. The accessions with resistance to tan spot identified in this study should be useful sources for developing new tan spot resistant cultivars.