THE ORIGIN OF A NEW PHYSIOLOGIC RACE OF CROWN RUST VIRULENT ON THE OAT VARIETIES VICTORIA AND SAIA

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Abstract
A new physiologic race of crown rust, Puccinia coronata Corda f. sp. avenae Erikss., was isolated from oats collected in four Canadian provinces in 1962. This race, 332, is one of the first reported that is capable of attacking both the differential oat varieties Victoria and Saia. A close relationship exists between race 332 and race 216, which suggests that the former may have arisen from the latter by mutation. The evolution of this new race has occurred in the absence of any known Saia type resistance in current commercial varieties, and its survival points up the operation of selective forces other than host resistance on the racial composition of the pathogenic population.