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- Six new Phytophthora species from ITS Clade 7a including two sexually functional heterothallic hybrid species detected in natural ecosystems in TaiwanPublication . Jung, Thomas; Horta, Marília; Scanu, B.; Seress, D.; Kovacs, G. M.; Maia, Cristiana; Perez-Sierra, A.; Chang, T. -T.; Chandelier, A.; Heungens, K.; van Poucke, K.; Abad-Campos, P.; Leon, M.; Cacciola, S. O.; Bakonyi, J.During a survey of Phytophthora diversity in natural ecosystems in Taiwan six new species were detected. Multigene phylogeny based on the nuclear ITS, beta-tubulin and HSP90 and the mitochondrial cox1 and NADH1 gene sequences demonstrated that they belong to ITS Clade 7a with P. europaea, P. uniformis, P. rubi and P. cambivora being their closest relatives. All six new species differed from each other and from related species by a unique combination of morphological characters, the breeding system, cardinal temperatures and growth rates. Four homothallic species, P. attenuata, P. flexuosa, P. formosa and P. intricata, were isolated from rhizosphere soil of healthy forests of Fagus hayatae, Quercus glandulifera, Q. tarokoensis, Castanopsis carlesii, Chamaecyparis formosensis and Araucaria cunninghamii. Two heterothallic species, P. xheterohybrida and P. xincrassata, were exclusively detected in three forest streams. All P. xincrassata isolates belonged to the A2 mating type while isolates of P. xheterohybrida represented both mating types with oospore abortion rates according to Mendelian ratios (4-33 %). Multiple heterozygous positions in their ITS, beta-tubulin and HSP90 gene sequences indicate that P. xheterohybrida, P. xincrassata and P. cambivora are interspecific hybrids. Consequently, P. cambivora is re-described as P. xcambivora without nomenclatural act. Pathogenicity trials on seedlings of Castanea sativa, Fagus sylvatica and Q. suber indicate that all six new species might pose a potential threat to European forests.
- Diversity of Phytophthora Species from Declining Mediterranean Maquis Vegetation, including Two New Species, Phytophthora crassamura and P. ornamentata sp nov.Publication . Scanu, Bruno; Linaldeddu, Benedetto T.; Deidda, Antonio; Jung, ThomasThe Mediterranean basin is recognized as a global biodiversity hotspot accounting for more than 25,000 plant species that represent almost 10% of the world's vascular flora. In particular, the maquis vegetation on Mediterranean islands and archipelagos constitutes an important resource of the Mediterranean plant diversity due to its high rate of endemism. Since 2009, a severe and widespread dieback and mortality of Quercus ilex trees and several other plant species of the Mediterranean maquis has been observed in the National Park of La Maddalena archipelago (northeast Sardinia, Italy). Infected plants showed severe decline symptoms and a significant reduction of natural regeneration. First studies revealed the involvement of the highly invasive wide-host range pathogen Phytophthora cinnamomi and several fungal pathogens. Subsequent detailed research led to a better understanding of these epidemics showing that multiple Phytophthora spp. were involved, some of them unknown to science. In total, nine Phytophthora species were isolated from rhizosphere soil samples collected from around symptomatic trees and shrubs including Asparagus albus, Cistus sp., Juniperus phoenicea, J. oxycedrus, Pistacia lentiscus and Rhamnus alaternus. Based on morphological characters, growth-temperature relations and sequence analysis of the ITS and cox1 gene regions, the isolates were identified as Phytophthora asparagi, P. bilorbang, P. cinnamomi, P. cryptogea, P. gonapodyides, P. melonis, P. syringae and two new Clade 6 taxa which are here described as P. crassamura sp. nov. and P. ornamentata sp. nov. Pathogenicity tests supported their possible involvement in the severe decline that is currently threatening the Mediterranean maquis vegetation in the La Maddalena archipelago.
- 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.
- Phytophthora pachypleura sp nov., a new species causing root rot of Aucuba japonica and other ornamentals in the United KingdomPublication . Henricot, B.; Perez Sierra, A.; Jung, ThomasIsolates of an unknown Phytophthora species from the Phytophthora citricola complex' have been found associated with mortality of Aucuba japonica in the UK. Based on morphological characteristics, growth-temperature relationships, sequences of five DNA regions and pathogenicity assays, the proposed novel species is described as Phytophthora pachypleura. Being homothallic with paragynous antheridia and semipapillate sporangia, P.pachypleura resembles other species in the P.citricola complex' but can be discriminated by its distinctively thick-walled oospores with an oospore wall index of 071. In the phylogenetic analysis based on three nuclear (ITS, -tubulin, EF-1) and two mitochondrial (cox1, nadh1) DNA regions, P.pachypleura formed a distinct clade within the P.citricola complex' with P.citricola s. str., P.citricola E and P.acerina as its closest relatives. Phytophthora pachypleura is more aggressive to A.japonica than P.plurivora and P.multivora and has the potential to affect other ornamental species.