A critical revision of the powdery mildew fungi (Erysiphaceae, Ascomycota) of Ukraine: Erysiphe sect. Microsphaera

The article continues a series of critical reviews of the species composition of powdery mildew fungi (Erysiphaceae, Helotiales, Ascomycota) of Ukraine and their distribution within the country. This article deals with species of the section Microsphaera of the genus Erysiphe. These species are distinguished by fruiting bodies that have non-mycelioid appendages with dichotomously branched apices. A list of 36 species of the section Microsphaera recorded in Ukraine with their distribution by regions is provided, as well as a key for their identification. The most common species frequently occurring in many regions of Ukraine are E. alphitoides, E. astragali, E. berberidis, E. divaricata, E. ehrenbergii, E. euonymi, E. ornata var. europaea, E. palczewskii, E. syringae-japonicae, and E. trifoliorum. Other species, such as E. baeumleri, E. elevata, E. euonymicola, E. friesii, E. grossulariae, E. hyperici, E. hypophylla, E. ornata var. ornata, E. penicillata, E. pseudoacaciae, E. robiniae, E. syringae, E. tortilis, E. vanbruntiana, and E. viburni, were recorded less often. Erysiphe azaleae, E. begoniicola, E. corylacearum, E. deutziae, E. gorlenkoi, E. guarinonii, E. magnifica, E. magnusii, E. platani, E. rayssiae, E. russellii, and E. symphoricarpi are known only from some localities. A number of species are invasive fungi mostly recorded in Ukraine relatively recently, within the last hundred years. Of them, E. alphitoides, E. palczewskii, E. syringae-japonicae, and E. vanbruntiana have become common species in Ukraine. Erysiphe azaleae, E. elevata, and E. platani can massively develop in certain regions or localities. The recently registered E. corylacearum is apparently becoming widespread in the Carpathians, E. ravenelii and E. symphoricarpi at present frequently occur in Kyiv. Some species, such as E. begoniicola, E. deutziae, E. euonymicola, E. guarinonii, E. magnifica, and E. russellii, are known from a few localities; however, in Kyiv magnolias are commonly infected by E. magnifica. At the same time, the North American species E. syringae has disappeared in Ukraine since the East Asian fungus E. syringae-japonicae started to spread on lilac. The indigenous fungus E. robiniae has also ceased to occur on Caragana arborescens, being completely replaced by the East Asian species E. palczewskii.