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Genetics

Inheritance of a Morphological Factor Limiting Infection by Ustilago hordei. W. Pedersen, Postdoctoral Fellow, Department of Plant Pathology, University of Nebraska, Lincoln, NE 68583; L. Jensen(2), R. L. Kiesling(3), and L. Darlington(4). (2)Plant Pathologist, Jensen Spraying Inc., Pocahontas, IA 50574; (3)Professor and Chairman, Department of Plant Pathology, North Dakota State University, Fargo, ND 58102; (4)Plant Pathologist, Tela Railroad Co., La Lima, Honduras, C.A. Phytopathology 67:1397-1399. Accepted for publication 2 May 1977. Copyright © 1977 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-67-1397.

Matings of compatible sporidial cultures from ordered tetrads from single teliospores of race 8, of Ustilago hordei sometimes failed to infect the highly susceptible barley cultivar, Odessa (C.I. 934). When the infection failed on Odessa, no infection was found on any other barley cultivars inoculated with the same culture. Matings of sporidial cultures from ordered tetrads of single teliospores which were derived from a single sporidial mating of race 8 wild type resulted in a ratio of three virulent to one avirulent dikaryon. Pathogenicity was always associated with the production of large numbers of infection hyphae of normal length and growth rate. Teliospores were selected from each virulent line, and sporidial cultures from their ordered tetrads were mated. Matings from these F₃ tetrads segregated either in a 3:1 or a 4:0 ratio with virulence dominant. Testcrosses of sporidial cultures of tetrads from F₂ teliospores confirmed that a single recessive gene conditioned the development of infection hyphae. Microscopic examination of the avirulent matings showed a decrease in both length and number of the infection hyphae compared with those of pathogenic matings from the same tetrad. The gene pair, ihi ihi, conditions poor development of infection hyphae.