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- Phytophthora acerina sp nov., a new species causing bleeding cankers and dieback of Acer pseudoplatanus trees in planted forests in northern ItalyPublication . Ginetti, Beatrice; Moricca, S.; Squires, J. N.; Cooke, D. E. L.; Ragazzi, A.; Jung, T.A severe dieback of Acer pseudoplatanus trees was noticed in planted forest stands in northern Italy in 2010. Affected trees showed collar rot and aerial bleeding cankers along the stems, leading to crown dieback and eventually death. An unknown Phytophthora species was consistently isolated from necrotic bark and xylem tissue and from rhizosphere soil. Based on its unique combination of morphological and physiological characters and phylogenetic analysis, this new taxon is here described as Phytophthora acerina sp. nov. Phylogenetic analysis of ITS, cox1 and beta-tubulin gene regions demonstrated that P. acerina is unique and forms a separate cluster within the 'P. citricola complex', closely related to P. plurivora. Phytophthora acerina is homothallic with smooth-walled oogonia, thick-walled, mostly aplerotic oospores with a high abortion rate, paragynous antheridia, and persistent, morphologically variable semipapillate sporangia. Four to 5-week-old cultures produced globose to subglobose, appressoria-like and coralloid hyphal swellings and characteristic stromata-like hyphal aggregations. Optimum and maximum temperatures for growth are 25 degrees C and 32 degrees C, respectively. Genetic uniformity of all 15 studied isolates and the apparent absence of this species in the extensive surveys of nurseries, forests and seminatural ecosystems conducted in the previous two decades across Europe indicate a recent clonal introduction to northern Italy. Under-bark inoculation tests demonstrated high aggressiveness of P. acerina to A. pseudoplatanus indicating that this pathogen might be a serious risk to maple plantations and forests in Europe.
- Widespread Phytophthora infestations in European nurseries put forest, semi-natural and horticultural ecosystems at high risk of Phytophthora diseasesPublication . Jung, Thomas; Orlikowski, L.; Henricot, B.; Abad-Campos, P.; Aday, A. G.; Aguin Casal, O.; Bakonyi, J.; Cacciola, S. O.; Cech, T.; Chavarriaga, D.; Corcobado, T.; Cravador, A.; Decourcelle, T.; Denton, G.; Diamandis, S.; Dogmus-Lehtijaervi, H. T.; Franceschini, A.; Ginetti, Beatrice; Green, S.; Glavendekic, M.; Hantula, J.; Hartmann, G.; Herrero, M.; Ivic, D.; Horta Jung, Marília; Lilja, A.; Keca, N.; Kramarets, V.; Lyubenova, A.; Machado, H.; Magnano di San Lio, G.; Mansilla Vazquez, P. J.; Marcais, B.; Matsiakh, I.; Milenkovic, I.; Moricca, S.; Nagy, Z. A.; Nechwatal, J.; Olsson, C.; Oszako, T.; Pane, A.; Paplomatas, E. J.; Pintos Varela, C.; Prospero, S.; Rial Martinez, C.; Rigling, D.; Robin, C.; Rytkoenen, A.; Sanchez, M. E.; Sanz Ros, A. V.; Scanu, B.; Schlenzig, A.; Schumacher, J.; Slavov, S.; Solla, A.; Sousa, E.; Stenlid, J.; Talgo, V.; Tomic, Z.; Tsopelas, P.; Vannini, A.; Vettraino, A. M.; Wenneker, M.; Woodward, S.; Perez-Sierra, A.An analysis of incidence of Phytophthora spp. in 732 European nurseries producing forest transplants, larger specimen trees, landscape plants and ornamentals, plus 2525 areas in which trees and shrubs were planted, is presented based on work conducted by 38 research groups in 23 European countries between 1972 and 2013. Forty-nine Phytophthora taxa were recorded in 670 nurseries (91.5%); within these nurseries, 1614 of 1992 nursery stands (81.0%) were infested, although most affected plants appeared healthy. In forest and landscape plantings, 56 Phytophthora taxa were recovered from 1667 of 2525 tested sites (66.0%). Affected plants frequently showed symptoms such as crown thinning, chlorosis and dieback caused by extensive fine root losses and/or collar rot. Many well-known highly damaging host-Phytophthora combinations were frequently detected but 297 and 407 new Phytophthora-host associations were also observed in nurseries and plantings, respectively. On average, 1.3 Phytophthora species/taxa per infested nursery stand and planting site were isolated. At least 47 of the 68 Phytophthora species/taxa detected in nurseries and plantings were exotic species several of which are considered well established in both nurseries and plantings in Europe. Seven known Phytophthora species/taxa were found for the first time in Europe, while 10 taxa had not been previously recorded from nurseries or plantings; in addition, 5 taxa were first detections on woody plant species. Seven Phytophthora taxa were previously unknown to science. The reasons for these failures of plant biosecurity in Europe, implications for forest and semi-natural ecosystems and possible ways to improve biosecurity are discussed.