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Slow Leaf-Rusting Resistance in Wheat Against Twenty-Two Isolates of Puccinia recondita. R. C. Kuhn, Graduate Research Assistant, Department of Agronomy, Purdue University, West Lafayette, IN 47907; H. W. Ohm(2), and G. E. Shaner(3). (2)Associate Professor, Department of Agronomy, Purdue University, West Lafayette, IN 47907; (3)Associate Professor, Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907. Phytopathology 68:651-656. Accepted for publication 14 October 1977. Copyright 1978 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-68-651.

In previous studies, a single isolate of Puccinia recondita developed more slowly on winter wheat cultivars Purdue 6028A2-5-9-6-1 (P6028) and Suwon 85 than on Suwon 92 and Monon. In this study, we measured the development of 22 isolates of P. recondita on these four cultivars in a growth chamber to test the race nonspecificity of the slow leaf-rusting resistances of P6028 and Suwon 85. For a given isolate of the pathogen, only cultivars that developed a susceptible reaction type were compared. Thus, the development of five isolates on P6028 and 21 isolates on Suwon 85 was compared to their development on Monon and Suwon 92. For all five isolates on P6028, and for 17 isolates on Suwon 85, the latent period was longer, a lower percentage of infection sites developed into pustules, there were fewer pustules per unit area of leaf, and pustules were smaller at 10-14 days after inoculation than on Monon or Suwon 92. The other four isolates were exceptions to these trends because of greater resistance to them by Monon and Suwon 92. The development of these four isolates on Suwon 85 was similar to the development of the other 17 isolates on this cultivar. Final pustule size was similar on all cultivars, although pustules reached this size on P6028 and Suwon 85 later than on Monon and Suwon 92. As measured in this study, slow leaf-rusting is race-nonspecific and should be long lasting.

Additional keywords: horizontal resistance, general resistance, Triticum aestivum, epidemiology, breeding for resistance.