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Resistance

Influence of Genes for Resistance to Puccinia coronata from Avena sterilis on Yield and Rust Reaction of Cultivated Oats. M. D. Simons, Plant pathologist, Agricultural Research, Science and Education Administration, U.S. Department of Agriculture, Department of Botany and Plant Pathology, Iowa State University, Ames, IA 50011; Phytopathology 69:450-452. Accepted for publication 25 October 1978. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1979. DOI: 10.1094/Phyto-69-450.

A strain of the wild oat (Avena sterilis) known to carry a gene for resistance to Puccinia coronata was crossed with a susceptible cultivated oat (A. sativa). Lines started as F₃ plants were carried to F₅ in bulk. Two plants of cultivated type, one resistant and one susceptible, were selected from each of 11 F₅ lines. In addition, 33 resistant and 29 susceptible plants descended from different F₃’s were selected in F₅. All lines were grown in F₇ and F₈, in replicated hill-plot field trials, and plants were exposed to artificially induced epidemics of crown rust. In duplicate trials, plants were maintained free of rust by use of a fungicide to measure any loss in yield or seed weight caused by crown rust. In the rust-free plots, the mean yield of the 11 resistant sister selections was 23% below the mean yield of their susceptible counterparts, and the mean yield of all 44 resistant lines was 10% below that of all 40 susceptible lines. Both the susceptible and the resistant lines varied significantly in response to infection, as measured by reductions in yield and seed weight caused by crown rust. Presumably, the variation was caused by minor genes for tolerance or by a low level of field resistance from the A. sterilis parent.