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Genetics

Variation in Aggressiveness Among and Within Races of Ustilago hordei on Barley. D. A. Gaudet, Former graduate research assistant, Department of Plant Pathology, North Dakota State University, Fargo 58105, Current address: Agriculture Canada Research Station, Lethbridge, Alberta, Canada T1J 4B1; R. L. Kiesling, professor emeritus, Department of Plant Pathology, North Dakota State University, Fargo 58105. Phytopathology 81:1385-1390. Accepted for publication 24 May 1991. Copyright 1991 Department of Agriculture, Government of Canada. DOI: 10.1094/Phyto-81-1385.

Components of aggressiveness and disease severity among 13 physiological races of Ustilago hordei on Hannchen, Nepal, and Odessa barley were studied to determine inter- and intrarace variability. Variation was observed among the physiological races of U. hordei for the aggressiveness components of peduncle compaction and extent of sorus formation in heads, leaves, and nodes. Variation within races 1, 7, 8, and 12, determined by using random sporidial crosses originating from different teliospores within a race collection inoculated onto Odessa, was observed for extent of peduncle compaction, plant dwarfing, and sorus formation in heads, leaves, and nodes. These race collections were heterozygous for gene(s) governing these traits. Races 7 and 12 were the most variable for these components and races 1 and 8 were the least.