VIEW ARTICLE

Resistance

The Residual and Interactive Expressions of 'Defeated' Wheat Stem Rust Resistance Genes. Uzi Brodny, Former senior project associate, Department of Plant Pathology, The Pennsylvania State University, University Park 16802, Present address: The George S. Wise Faculty of Life Sciences, Institute for Cereal Crops Improvement, Tel Aviv University, Tel Aviv 69978, Israel; R. R. Nelson(2), and L. V. Gregory(3). (2)(3)Evan Pugh Professor, and research assistant, respectively, Department of Plant Pathology, The Pennsylvania State University, University Park 16802. Phytopathology 76:546-549. Accepted for publication 2 December 1985. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/Phyto-76-546.

Seven near-isogenic lines of Chinese Spring wheat and Red Egyptian (CI 14181) representing all combinations of the resistance alleles Sr6, Sr8, and Sr9a were studied for their reaction to an isolate of Puccinia graminis f. sp. tritici race RKQQ that possesses virulence alleles corresponding to Sr6, Sr8, and Sr9a. The seven lines with one or more of the resistance genes significantly reduced pustule size and sporulation compared to the Chinese Spring control line. Lines with two resistance genes were more effective in reducing pustule size and sporulation than were lines with single resistance genes. The line with three resistance genes was more effective in reducing pustule size and sporulation than lines with two genes. We conclude that each of the three resistance genes has a residual expression when confronted by matching virulence genes.