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Resistance

Un8 Allele for Loose Smut Resistance Associated with Necrosis in Embryos of Infected Barley. B. K. Gabor, Agriculture Canada Research Station, 195 Dafoe Road, Winnipeg, Manitoba, Canada R3T 2M9; P. L. Thomas, Agriculture Canada Research Station, 195 Dafoe Road, Winnipeg, Manitoba, Canada R3T 2M9. Phytopathology 77:533-538. Accepted for publication 18 July 1986. Copyright 1987 Department of Agriculture, Government of Canada.. DOI: 10.1094/Phyto-77-533.

The barley line CI 13662 carries the Un8 allele for resistance to loose smut. Inoculated florets of this line produce seeds from which adult plants are free from sporulation. Extensive necrosis was histologically observed in the embryos of inoculated seeds, but not in seed of cultivars in which resistance is conditioned by dominant alleles at three other loci. The stage of plant growth at which resistance was expressed was also different. The alleles Un3 and Un6, in the cultivars Jet and Conquest, appeared to confer resistance in the seedling stage. The allele Un, in the cultivars Trebi and Warrior, appeared to confer resistance in which penetration of the embryo was inhibited. Electron microscopy showed that the necrosis of cells of embryos of CI 13662 was accompanied by secondary wall thickening and vacuolization in the host and by necrosis of hyphae in the fungus.