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Conservation of Scald Resistance in Barley Composite Cross Populations. L. F. Jackson, Postgraduate Research Plant Pathologist, Department of Plant Pathology, University of California, Davis CA 95616; A. L. Kahler(2), R. K. Webster(3), R. W. Allard(4). (2)(3)(4)Research Associate, Department of Genetics, Professor, Department of Plant Pathology and Professor, Department of Genetics and Department of Agronomy, University of California, Davis CA 95616. Phytopathology 68:645-650. Accepted for publication 5 October 1977. Copyright 1978 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-68-645.

The barley-Rhynchosporium secalis host-parasite system was used as a model to evaluate the potential of barley (Hordeum vulgare) composite cross populations for conservation of disease resistance alleles. Four isolates of R. secalis were used to monitor the frequencies of specific scald resistances through early, intermediate, and late generations of three composite cross populations (CCII, CCV, CC XXI). Resistance to each isolate was maintained through the latest generation tested of each population. Changes in the frequencies of plants resistant to particular isolates were observed between generations in all three populations. In CC II, resistance to three of the four isolates changed from relatively low to extremely high frequencies by generation F47. Trends in frequencies of resistance are discussed in relation to the conservation of genes for disease resistance, and the degree of disease control provided by genetically diverse populations.

Additional keywords: plant breeding.