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Epidemiology

General Resistance Displayed by Three Hard Red Spring Wheat (Triticum aestivum) Cultivars to Leaf Rust. Glen D. Statler, Associate Professor of Plant Pathology, North Dakota State University, Fargo, ND 58102; John E. Watkins(2) and John Nordgaard(3). (2)Assistant Professor of Plant Pathology, University of Nebraska, Lincoln, NB 68503; (3)Plant Pathologist, Northwood, ND 58267. Phytopathology 67:759-762. Accepted for publication 20 December 1976. Copyright © 1977 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-67-759.

Hard red spring wheat (Triticum aestivum) cultivars, Justin, Fortuna, and Tioga with susceptible reaction types to Puccinia recondita tritici, which causes leaf rust were evaluated for general resistance. Percentage disease severity and reaction type were evaluated periodically. Logit analyses of disease progress curves were computed to compare the apparent infection rate (AIR) for several cultivars. Cultivars Justin, Fortuna, and Tioga consistently exhibited less leaf rust in the field and slower rates of rust development than Thatcher. Rust increased earlier in the season and more rapidly on Thatcher than on the other cultivars. The high correlation coefficient between AIR and rust severity indicated final rust severity could be used as an indication of AIR. The high correlation for AIR between the flag, flag-1, and lower leaves indicated that rate of rust development on a given cultivar could be measured on any leaf. Yields of Justin, Fortuna, and Tioga were not increased by controlling leaf rust with systemic fungicide but yields of Thatcher were usually increased significantly. General resistance was indicated for Justin, Fortuna, and Tioga since they always exhibited a slower rate of rust development and lower rust severities at the end of the evaluation period than did Thatcher. The general resistance displayed by these cultivars apparently provides partial protection against leaf rust infection under North Dakota conditions.