Influence of Genes for Resistance toPuccinia coronatafromAvena sterilison Yield and Rust Reaction of Cultivated Oats

Abstract

A strain of the wild oat (A. sterilis) known to carry a gene for resistance to P. 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, 1 resistant and 1 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.