Pathogenicity of Gaeumannomyces graminis isolates to wheat and rye seedlings

A total of 187 isolates of Gaeumannomyces graminis , obtained from diseased cereal roots between 1979 and 1983, mostly from the UK, were compared for their ability to produce disease on wheat and rye seedlings in the glasshouse. Isolates varied continuously in pathogenic adaptation to rye. from those infecting wheat substantially and rye slightly (designated normal or N‐isolates) to those infecting both wheat and rye substantially (designated R‐isolates). The degree of adaptation to rye was a consistent characteristic of individual isolates. All were morphologically similar to G. graminis var. tritici R‐isolates were obtained from all the areas sampled, they did not appear to predominate on a particular host species and occurred together with N‐isolates and intermediates in a single field.