ORIGINAL ARTICLE Genetic diversity and host range of powdery mildews on Papaveraceae Katarína Pastirčáková 1 & Tünde Jankovics 2 & Judit Komáromi 3 & Alexandra Pintye 2 & Martin Pastirčák 4 Received: 29 September 2015 /Revised: 19 February 2016 /Accepted: 23 February 2016 # German Mycological Society and Springer-Verlag Berlin Heidelberg 2016 Abstract Because of the strong morphological similarity of the powdery mildew fungi that infect papaveraceous hosts, a total of 39 samples were studied to reveal the phylogeny and host range of these fungi. ITS and 28S sequence analyses revealed that the isolates identified earlier as Erysiphe cruciferarum on papaveraceous hosts represent distinct line- ages and differ from that of E. cruciferarum sensu stricto on brassicaceous hosts. The taxonomic status of the anamorph infecting Eschscholzia californica was revised, and therefore, a new species name, Erysiphe eschscholziae, is proposed. The taxonomic position of the Pseudoidium anamorphs infecting Glaucium flavum, Meconopsis cambrica, Papaver dubium, and Stylophorum diphyllum remain unclear. This study re- vealed that Erysiphe macleayae exhibits a specific host range different from that of E. cruciferarum, the common pathogen of papaveraceous hosts. Although E. macleayae occurred nat- urally on Macleaya cordata, Macleaya microcarpa, M. cambrica, and Chelidonium majus only, our inoculation tests revealed that the fungus was capable of infecting Argemone grandiflora, Glaucium corniculatum, Papaver rhoeas, and Papaver somniferum, indicating that these plant species may also be taken into account as potential hosts. Erysiphe cruciferarum originating from P. somniferum was not able to infect A. grandiflora, C. majus, E. californica, M. cordata, and P. rhoeas. The emergence of E. macleayae on M. microcarpa is reported here for the first time from the Czech Republic and Slovakia. The appearance of chasmothecia of E. macleayae on C. majus in Slovakia was reported, as well. Erysiphe cruciferarum was identified on G. corniculatum and reported here for the first time from Slovakia. Keywords Erysiphaceae . Eschscholzia . Macleaya . ITS . 28S nrDNA . Morphology Introduction Asexual morphs of powdery mildews belonging to the same genus are, in many cases, morphologically indistinguishable from each other. Therefore, their identification is often com- plicated, especially in the absence of the sexual morphs (chasmothecia), and sometimes questionable based exclusive- ly on morphological data. The identification might be more problematic in those particular cases when one host plant spe- cies is infected by more than one asexual powdery mildew fungi with highly similar morphologies (Cook et al. 1997). On the other hand, morphologically indistinguishable asexual morphs may represent genetically distinct lineages that seem to be specialized to one or a few host plant species belonging even to different plant families. Recently, phylogenetic Section Editor: Franz Oberwinkler Taxonomic novelty Erysiphe eschscholziae Pastirč. & Jankovics Katarína Pastirčáková and Tünde Jankovics contributed equally to this work. * Katarína Pastirčáková uefezima@hotmail.com 1 Institute of Forest Ecology, Branch for Woody Plant Biology, Slovak Academy of Sciences, Akademicka 2, SK-94901 Nitra, Slovakia 2 Plant Protection Institute, Centre for Agricultural Research, Hungarian Academy of Sciences, P.O. Box 102, H-1525 Budapest, Hungary 3 Agricultural Institute, Centre for Agricultural Research, Hungarian Academy of Sciences, Brunszvik u. 2, H-2462 Martonvásár, Hungary 4 Research Institute of Plant Production, National Agricultural and Food Centre, Bratislavska cesta 122, SK-92168 Piestany, Slovakia Mycol Progress (2016) 15:36 DOI 10.1007/s11557-016-1178-8