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Resistance

Characterization of Resistance to Leaf Rust in Pacific Northwest Wheats. E. A. Milus, Research assistant, Department of Plant Pathology, Washington State University, Pullman, WA 99164, Present address: Department of Plant Pathology, North Carolina State University, Raleigh, NC 27607; R. F. Line, plant pathologist, Agricultural Research, Science and Education Administration, U. S. Department of Agriculture, Pullman, WA 99164. Phytopathology 70:167-172. Accepted for publication 27 August 1979. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1980. DOI: 10.1094/Phyto-70-167.

Seven types of resistance to two local cultures of Puccinia recondita were identified by determining numbers of uredia per square centimeter of leaf surface, length of latent period, number of spores per uredium, and infection type (size of uredia and lesions) on seedling and adult plants of nine Pacific Northwest wheat cultivars. Two cultivars were fully susceptible to both cultures. One cultivar had hypersensitive resistance to one of the P. recondita cultures. The remaining six cultivars had various degrees of slow rusting in the field. As measured by the above components, two of these cultivars expressed resistance only in the adult plant stage, and four expressed resistance in both the adult and seedling stages. These four cultivars also showed culture cultivar interactions for the above components of resistance, which indicates that slow rusting in them is culture-specific. When cultivars had fewer uredia, longer latent periods, and fewer spores per uredium they also had a range of high to low infection types (large to small uredia and lesions). The association between a range of infection types and other components of resistance may be useful for selecting breeding lines that are slow rusting.

Additional keywords: specific resistance, nonspecific resistance.