Phytophthora cactorum causing bleeding canker of common beech, horse chestnut, and white poplar in the Czech Republic

Abstract

In 2007, declining mature trees of common beech ( Fagus sylvatica ), horse chestnut ( Aesculus hippocastanum ), and white poplar ( Populus alba ) with bleeding cankers were found in several locations in the Central Bohemia region. The morphological and cultural characteristics of isolates from diseased tissues were consistent with those of Phytophthora cactorum (Erwin & Ribeiro, 1996). The colonies were stellate to rosaceous, appressed with slight aerial mycelium on V8 agar. Radial growth was 8-14 mm day -1 at 20 ° C. Optimum growth temperature was 23-25 ° C, minimum 3-8 ° C and maximum 30-33 ° C. Strains were homothallic, produced abundant terminal, smooth-walled, spherical oogonia (20 -35 μ m in diameter). Oospores were plerotic or nearly plerotic, 22-31 μ m in diameter and the oospore wall 1·0-2·2 μ m thick. Antheridia were para-gynous, but amphigynous antheridia also occurred in up to a quarter of cases. Sporangiophores were sympodial, sporangia ellipsoidal, ovoid to subglobose, papillate and measured 17-38 × 14-30 μ m (L:B ratio 1·05-1·80).Comparison of DNA sequences of ITS region of representative isolates from all hosts (GenBank Acc. Nos. EU562207-EU562209) gave 99% identity to P. cactorum . Isolates were deposited at Culture Collection of Fungi, Prague under CCF Nos. 3757, 3758, 3762.The pathogenicity was tested using 20, 1-year-old saplings of all three hosts. Wounds (5 mm diam.) on stems of ten saplings of each host were artificially inoculated by plugs of V8 agar from the actively growing colony margins of isolates and the wounds were sealed by Parafilm. The characteristic stem necroses developed after 1-2 weeks on all plants. Stems of many beech and horse chestnut saplings were girdled in 2 to 3 months and in c . 33% of poplars, with the majority of poplar saplings forming callus and surviving the infection. The pathogen was successfully reisolated from plants showing symptoms. The control plants inoculated in the same way with sterile agar plugs remained healthy.Phytophthora cactorum is well known pathogen of beech and horse chestnut (Brasier & Strouts, 1976;Jung et al ., 2005), but not reported on any poplar species. This is the first report of P. cactorum causing bleeding canker of common beech and horse chestnut in the Czech Republic and the first record of it on white poplar. Acknowledgement

The survey of some factors affecting bark lesion development caused by Phytophthora cactorum on common beech and other broadleaved trees

“…Our results (Mrazkova 2007;Cerny et al 2008Cerny et al , 2009Černý et al 2008;Mrázková 2008; this study) confirmed that Phytophthora spp. causing diseases of woody plants should be taken more seriously in the Czech Republic.…”

“…The isolates of P. cactorum were acquired from stem lesions of white poplar, common beech and horse chestnut. The identity of the isolates was verified by morphological analysis as well as by the analysis of the ITS regions (Cerny et al 2009). P. cactorum isolates are deposited in the Silva Tarouca Research Institute for Landscape and Ornamental Gardening (RILOG) culture collection, Culture Collection of Fungi (Prague) and their sequencies in GenBank.…”

“…EU562207), P078.07 (common beech, CCF 3768, GenBank EU638290) and P100.07 (horse chestnut, CCF 3762, GenBank EU562209). The short morphological description of the species was given in Cerny et al (2009). The isolates of the other Phytophthora species used in the experiments are deposited in RILOG culture collection and four of them in Culture Collection of Fungi (CCF), Prague.…”

“…The first authentic isolates of Phytophthora cactorum were acquired during the contemporary investigation of phytophthora diseases of forest and ornamental woody plants from beech, white poplar, horse chestnut and rhododendron (Mráz-ková et al 2008;Cerny et al 2009). Although the investigations leading to definition of the host spectrum and to decription of the pathogen variability in the Czech Republic have still been in progress, we started the experiments concerned with the pathogenicity of P. cactorum to forest tree species.…”

Horse Chestnut Bleeding Canker Caused by Pseudomonas Syringae Pv. Aesculi in the Czech Republic

“…By contrast, isolation of the bacterium Pseudomonas syringae was shown to be associated with the increased occurrence of bleeding canker (Dijkshoorn-Dekker 2005). However, up until 2008, no new oozing occurred and the symptoms disappeared or, in one case, were identified as being caused by Phytophthora cactorum (Cerny et al 2009). The occurrence of bleeding canker of horse chestnut trees has also been described in France (Bardoux and Rousseau 2007), Belgium and Ireland (EPPO Reporting Service 2011).…”