Heavily-melanized variants of the sexual Gaeumannomyces graminis var. tritici are non-pathogenic and indistinguishable from the asexual, Phialophora state

Gaeumannomyces graminis var. tritici is the aetiologic agent of take-all disease of wheat and barley. Heavily-melanized variants of a lightly pigmented, virulent wild-type strain were isolated and characterized. These variants were phenotypically similar to Phialophora sp., the proposed anamorph of Gaeumannomyces graminis var. tritici. Unlike the wild-type G. graminis strain, Phialophora -like variants produced conidia and lost their ability to reproduce sexually after serial transfer. Some ascospores from initial self-crosses of the Phialophora -like variants regained the G. graminis phenotype, and these derivatives could again produce Phialophora -like variants. As with Phialophora isolates from the field, Phialophora -like variants produced in this study were non-pathogenic and produced less extracellular protein.