A cryptic powdery mildew (Golovinomyces hieraciorum sp. nov.) on Hieracium and Pilosella (Compositae)

Abstract

The Golovinomyces cichoracearum complex is morphologically highly variable and causes powdery mildew on a wide range of Compositae, including Hieracium spp. and Lapsana communis. A comprehensive phylogenetic analysis of Golovinomyces, published in 2013, revealed that G. cichoracearum s. str. was confined to Scorzonera and Tragopogon spp. as hosts (Compositae, tribe Lactuceae, subtribe Scorzonerinae). To clarify the phylogeny and taxonomy of Golovinomyces on Hieracium spp. (Compositae, tribe Lactuceae, subtribe Hieraciinae), which is common in Asia and Europe, morphology and phylogenetic analyses of ITS + 28S rDNA sequences were conducted for 57 powdery mildew specimens of Hieracium spp. and Lapsana communis. Golovinomyces on Hieracium spp. in Asia and Europe, previously referred to as G. cichoracearum, is a previously undescribed, cryptic species, which is described here as Golovinomyces hieraciorum sp. nov.. Since a sequence retrieved from a powdery mildew on Lapsana communis in Switzerland clustered in sister position to the G. hieraciorum clade, numerous German specimens identified as G. cichoracearum were included in the present examinations. All the re-examined collections of “G. cichoracearum” on L. communis were misidentified, and were shown to belong to Neoërysiphe nevoi or Podosphaera ergerontis-canadensis.