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Histological Aspects of Dwarf Bunt Resistance in Wheat. John A. Fernández, Former Research Associate, Department of Plant Pathology, Washington State University, Pullman, WA 99164, Present address: Plant Science Division, College of Agriculture and Experiment Station, University of Wyoming, Laramie, WY 82071; Rubén Durán(2), and John F. Schafer(3). (2)(3)Professors, Department of Plant Pathology, Washington State University, Pullman, WA 99164. Phytopathology 68:1417-1421. Accepted for publication 20 April 1978. Copyright © 1978 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-68-1417.

Four wheat cultivars differing in resistance to race D-2 of Tilletia controversa were all initially infected following artificial inoculation. Following penetration of the coleoptile in plants of the highly susceptible cultivar Red Bobs, intercellular hyphae ramified throughout primordial leaf and nodal tissue, and reached cells of the growing point. The fungus was assumed to sporulate in plants so infected, provided hyphae reached the growing point before internodal elongation. This assumption was based on results of sectioning 40 Red Bobs seedlings at various intervals, 37 of which were shown to be infected, and on demonstrating bunt in 57 of 63 plants grown to maturity. In the resistant cultivars Requa and Nugaines, hyphae of the fungus followed a similar route, but almost always failed to invade cells of the growing point and thus failed to sporulate. In the highly resistant cultivar P.I. 178383, the few hyphae detected usually were confined to the first and second leaves well away from the growing point.