Katarína Pastirčáková

Genetic diversity and host range of powdery mildews on Papaveraceae

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 lineages 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 revealed that Erysiphe macleayae exhibits a specific host range different from that of E. cruciferarum, the common pathogen of papaveraceous hosts. Although E. macleayae occurred naturally 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.

Global Distribution of Erysiphe platani: New Records, Teleomorph Formation and Re-Examination of Herbarium Collections

Abstract A global survey of the spread of the Platanus powdery mildew, Erysiphe platani , has been carried out. E. platani teleomorph formation was recorded in countries where the fungus anamorph has been present for several years. The first findings of chasmothecia were recorded in Austria, Czech Republic, France, Italy and Slovakia. New records of E. platani (including the teleomorph) were found in Belgium, Croatia and Denmark. The occurrence of this fungus in Sweden and in two countries of North Africa (Algeria and Morocco) was confirmed. Descriptions of morphological features, illustrations, and worldwide distribution of E. platani are provided. Herbarium collections of powdery mildews on Platanus spp. were re-examined and revised. The occurrence of Phyllactinia guttata on Platanus is discussed and questioned.

Individual resistance of Fraxinus angustifolia and F. excelsior clones to Hymenoscyphus fraxineus

Ash dieback, caused by Hymenoscyphus fraxineus, is a serious disease of common and narrow-leaved ash in Europe. The resistance of individual trees seems to be important for the maintenance of ash in European forests. In this in situ wound inoculation study, the susceptibility and differences in resistance to H. fraxineus between Fraxinus excelsior and F. angustifolia clones were assessed. Neither of the tested clones revealed total resistance to ash dieback; variety between the tested clones was observed. Differences in necroses lengths were significant between clones and between two ash species. Longer necroses were formed in F. angustifolia than in F. excelsior. Some clones exhibiting some resistance to the pathogen were identified.

Species diversity of fungi on damaged branches and leaves of ashes (Fraxinus spp.) in different types of stands in Slovakia

Abstract The diversity of fungi on branches and leaves of ashes (Fraxinus angustifolia, F. excelsior, F. ornus) in Slovakia was studied. Symptomatic material collected in Slovakia during the period of 2013 to 2017 and herbarium specimens previously collected were examined. In total, 30 fungal taxa (15 Deuteromycetes, 14 Ascomycetes and one Basidiomycetes) were recorded. Twenty-three of them have never been recorded on ashes in the country. The most frequently occurring fungi were Hymenoscyphus fraxineus (anamorph Chalara fraxinea) that causes necrosis of shoots and branches, and Phyllactinia fraxini, a foliar pathogen that causes powdery mildew disease. Fungal diversity on ashes growing in different types of stands was compared. Species richness was the greatest in seed orchards (20 fungal taxa) compared to private gardens, which contained the lowest (two fungal taxa). Species diversity in forest stands comprised 18 fungal taxa and the urban greenery was represented by 10 fungal taxa. Nine fungal taxa were recorded in tree alley along the road. The widest fungal species spectrum was recorded on F. excelsior.

Powdery mildew of California poppy caused by Erysiphe eschscholziae in Mexico

Abstract Severe infection by powdery mildew was observed on California poppy (Eschscholzia californica) plants in Texcoco, State of Mexico, during spring of 2014 to 2017. Symptoms included colonies of white to greyish mildew-like growth on the abaxial and adaxial surfaces of the leaves. The identification of the fungal species was performed by examination of morphological structures using light microscopy and scanning electron microscope (SEM), as well as sequence analysis of the 5ʹ-end of 28S rRNA gene and the internal transcribed spacer (ITS) region of rDNA. Using the combination of morphological characterization and a phylogenetic analysis using Bayesian inference, the fungal agent was identified as Erysiphe eschscholziae. Pathogenicity tests were conducted on leaves of California poppy plants, and Koch’s postulates were fulfilled. This is the first report of E. eschscholziae causing powdery mildew on Eschscholzia californica in Mexico.

Two blue-stain fungi colonizing Scots pine (Pinus sylvestris) trees infested by bark beetles in Slovakia, Central Europe

Excessive mortality of Scots pine (Pinus sylvestris) trees has recently been observed in the Záhorská nížina lowland in western Slovakia, Central Europe. Continuous drought, bark beetles and blue-stain fungi are likely to play a crucial role in this dieback of pines in a warm sandy area. Two blue-stain fungi, Ophiostoma ips and Ophiostoma minus, were found here on Scots pine trunks infested by bark beetles. These fungi were isolated and identified based on morphological properties and DNA sequences (ITS, LSU, β-tubulin). They colonized the inner bark, phloem and blue-stained sapwood, and were recorded in the galleries of Orthotomicus longicollis and other species of this genus. The occurrence of O. minus was massive; the fungus was found to produce perithecia abundantly in dying pines. Detailed descriptions, illustrations and global distribution of the two fungal species on host pine species are provided. The records of O. ips and those of O. minus are new for the mycoflora of Slovakia. Undetermined mycophagous nematodes were found inside the perithecia of O. ips. The role of bark beetles as real and potential vectors (Ips spp., Orthotomicus spp., Tomicus spp., Hylurgus ligniperda, Hylastes sp.) of blue-stain fungi in a declining pine forest is discussed.