Population structure of Rosellinia desmazieresii causing ring-dying of Salix repens

Rosellinia desmazieresii was isolated from eleven disease rings in five different sand dune slacks at Ainsdale National Nature Reserve, U.K. Single ascospore isolates from the same perithecium, or wood- or ascospore-derived isolates from the same ring, were somatically compatible and morphologically identical, indicating a non-outcrossing breeding strategy. However, isolates from different rings were somatically incompatible in all cases, producing a pigmented demarcation zone when paired in culture, suggesting that each ring represented a distinct, clonally propagated genet.