Hymenoscyphus pseudoalbidus, the correct name for Lambertella albida reported from Japan

Recent molecular analyses separate Hymenoscyphus pseudoalbidus (causal agent of ash dieback in Europe) from the morphologically scarcely distinguishable H. albidus. Hymenoscyphus albidus was reported (as Lambertella albida) on petioles of Fraxinus mandshurica in Japan. Phylogenetic analysis in the present study shows Japanese L. albida to be conspecific with H. pseudoalbidus but with a higher genetic variability compared to European isolates. The presence of croziers at the ascus base was found to be a clear distinguishing character of H. pseudoalbidus. Our phylogenetic analysis of the combined ITS and LSU-D1/D2 dataset supports Hymenoscyphus as more appropriate than Lambertella for H. pseudoalbidus. As the Hymenoscyphus clade includes members with two major characters (presence of substratal stroma and brown ascospores) currently used to circumscribe Lambertella, the generic delimitation of Lambertella requires redefinition.