ABSTRACT
Helminthosporium victoriae was first described in 1946 as the causal agent of Victoria blight of oats. It proved to be a highly specialized pathogen since it inflicts its damage on only those oat varieties with the Victoria-type of resistance to crown rust Puccinia coronata. The disease caused by H. victoriae rose to epidemic proportions in 1947 and 1948 and caused serious reduction in yields in most oat-growing regions of the US The 145S virus is probably a multicomponent virus based on the multiplicity of density components resolved in CsCl gradients and the isolation of four distinct double-stranded ribonucleic acid (dsRNA) components. The relatedness of the dsRNA components of the 145S virus needs to be investigated. It is not known whether the multiple components of dsRNA represent a segmented genome or whether one or more of these components are satellites or deletion mutants.
