Distribution of Erysiphe platani (Erysiphales) in Ukraine

Information is provided on Erysiphe platani, a newly invasive fungus in Ukraine. The anamorph of this North American powdery mildew was first recorded in Ukraine in 1986 on Platanus orientalis in the Nikita Botanical Garden (Crimea). Later, it was found in other localities of the Crimean peninsula, and in Odessa and Odessa region on three species of plane, namely P. × hispanica, P. occidentalis and P. orientalis. Spread of the fungus was epiphytotic. This mildew significantly reduces the ornamental value of plane trees, which are often planted in public open spaces within urban areas of southern Ukraine. Recently, E. platani has formed the teleomorph in this region. Morphologically, the Ukrainian material is slightly different from the species description, viz. appendages are longer (up to 3 times the chasmothecial diam.), often with less compact apices.

Usually, alien species of powdery mildews entering Western Europe from North America, are soon recorded in Ukraine.Erysiphe platani was no exception.The fungus was first found by G. Ovcharenko in November 1986 on Platanus orientalis L. in the Nikita Botanical Garden in Crimea (Fig. 1).Collections were repeated the following year.Note that in both cases the fungus developed only the anamorphic state; therefore, it was later referred to a Pseudoidium sp.(Dudka et al. 2004).Obviously, some time later the mildew began to spread intensively in the south of Crimea, because in October and November 2005, samples (again only the anamorph) were collected on Platanus sp. by V.P. Heluta in Yalta, and L. Musatenko and L. Voitenko in Sevastopol.Still later, the fungus spread beyond the Crimea, and after 2010 it was repeatedly collected by V.G.Korytnianska in Odessa region.It infected at least two species of plane (P.× hispanica Mill.ex Muenchh.and P. occidentalis L.) and now formed fruiting bodies, allowing us to refer it to E. platani rather than merely to a Pseudoidium sp.

MATERIALS AND METHODS
Mycelium, conidiophores, conidia and chasmothecia were studied using dried herbarium specimens listed below.For light microscopy, mycelium, conidiophores and conidia were removed from the surface of infected leaves using transparent adhesive tape.To restore shape and size, a piece of tape with these fungus structures was put in a droplet of 40% lactic acid solution on a microscope slide, covered with a cover glass, gently heated to boiling point, then examined and photographed under a light microscope «Primo Star» (Carl Zeiss, Germany) using the Camera «Canon A 300» and software «AxioVision 4.7».Fruiting bodies were placed in a drop of distilled water.Digital data were treated statistically when n was ≥ 30 for each character.
The studied materials were deposited in the National Herbarium of M.G.Kholodny Institute of Botany of the National Academy of Sciences of Ukraine (KW).

RESULTS AND DISCUSSION
All specimens of powdery mildew collected on Platanus L. in Crimea and Odessa region of Ukraine were found to belong to E. platani, and generally corresponded to the description of this species, but their chasmothecial appendages are much longer (up to three times the chasmothecial diameter) than stated in the monograph by Braun and Cook (2012).Moreover, in some cases, our material was slightly distinguished by the elongation of some branches of the first or second order, so that apical parts of appendages could hardly be considered compact.In addition, one specimen of the fungus from Turkey (only anamorph) was identified making it the third record of E. platani in that country.Its morphology matched that of the Ukrainian material.
There follows a description, distribution, location, date of collection and micrographs of the species, and a brief discussion of the materials studied.
Mycelium mostly epiphyllous forming more or less pure white spots or amphigenous dirty-yellowish, irregular and diffuse patches (Fig. 2A).Anamorph of Pseudoidium type.Conidia very variable in shape and size, mainly elongated-ellipsoidal to ellipsoidal, often slightly vase-shaped, sometimes very elongated, to almost cylindrical with rounded ends, 32.5-37.0(-40.0)× 15.0-17.5(-20.0)μm (Fig. 2C).Chasmothecia numerous, scattered, sometimes only in groups on the underside of the leaf in places beneath patches of mycelium that formed on the upper side of the leaf, dark brown, hemispherical, impressed in the lower part, 85-125 μm diam.(Fig. 2B).note: All specimens from Odessa and Odessa region were collected by V. Korytnianska, so the name of the collector is not specified.
As already mentioned, the specimen of E. platani on Platanus sp.collected in Turkey, Antalya, Alanya, Konakli, in September 2011, leg.O. Peregrym (KW 40032F), was included in the study.
It should be noted that due to their high ornamental value, unpretentiousness and tolerance to adverse environmental conditions, plane-trees are widely used in landscaping of the southern cities of Ukraine.In Odessa they are represented by the three species, P. ×hispanica, P. occidentalis and P. orientalis, but only the first two are widely cultivated in the city (Kovalenko, Bonetsky 1985).Stately planetrees are a hallmark of the city and decorate the famous streets and boulevards, e.g.Rishelievska and Pushkinska Streets or Primorsky Boulevard.The oldest of them were given the special conservation status of 'botanichna pamiatka pryrody mistsevoho znachennia' (Popova et al. 2006).Unfortunately, powdery mildew caused by E. platani is very harmful to both old and young trees.A naturally dense down on young leaves that usually disappears as healthy leaves mature remains on damaged parts of the leaf.As a result of the disease, leaves are covered with a more or less thick white or grey coating of plant hairs combined with mycelium, conidiophores and conidia of the fungus.This often results in holes and cracks causing significant deformation of the lamina and young infected shoots often wither.Thus, trees lose appreciable ornamental value and become a source of additional air pollution due to the release of large numbers of conidia.The disease is already epiphytotic in Odessa and Odessa region.

Fig. 1 .
Fig.1.Distribution of Erysiphe platani in the southern part of Ukraine.(Findings are represented by black dots).