Browsing by Author "Schena, Leonardo"
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- Diversity of Phytophthora species in Valdivian rainforests and association with severe dieback symptomsPublication . Jung, Thomas; Durán, Alvaro; Stowasser, Eugenio Sanfuentes von; Schena, Leonardo; Mosca, Saveria; Fajardo, Sebastian; González, Mariela; Navarro Ortega, Angella D.; Bakonyi, Jozsef; Seress, Diana; Michal Tomšovský; Cravador, Alfredo; Maia, Cristiana; Marilia Horta Jung; Horta Jung, Marília; Jung, Thomas; Cravador, AlfredoThe Valdivian rainforest, one of the global hotspots of biodiversity, is a temperate rainforest originating as a Tertiary relic from the supercontinent Gondwana. In November 2014, a survey of Phytophthora diversity was performed in 13 natural forest stands and 20 forest streams and rivers in two protected areas near Valdivia and in a temperate montane forest in the Concepción area. One planted stand each of the introduced tree species Castanea sativa and Fagus sylvatica were also included. Using baiting assays, eight described species and four previously unknown taxa of Phytophthora were isolated from 86% of the 50 rhizosphere soil samples from seven of the eight tree species sampled in 12 forest stands, and from 20 streams: P. chlamydospora, P. cinnamomi, P. kernoviae, P. lacustris, P. plurivora, P. pseudosyringae, P. ×cambivora, P. ×stagnum, P. valdiviana nom. prov. from Clade 2b, P. madida nom. prov. from Clade 8a, and P. chilensis nom. prov. and P. pseudokernoviae nom. prov. The latter two species are the closest relatives of P. kernoviae from Clade 10. Phytophthora pseudokernoviae nom. prov. was also isolated from necrotic leaves of Drimys winteri. From the Valdivia river, a swarm of three Clade 6 hybrids was recovered. Each hybrid isolate resulted from multiple reticulation events with P. thermophila as maternal and both P. amnicola and P. chlamydospora as paternal parents. In addition, three previously unknown and recently described Nothophytophthora species, N. caduca, N. chlamydospora and N. valdiviana, were isolated from several forest streams. Phytophthora cinnamomi, the most common and widespread species in soils of native forests, was associated with severe dieback of Valdivian rainforest trees, in particular D. winteri, Luma apiculata, Nothofagus dombeyi and the endangered Saxegothaea conspicua. A first pathogenicity test demonstrated high aggressiveness of P. cinnamomi to several native tree species, including N. dombeyi, Blepharocalyx cruckshanksii and Gevuina avellana.
- High diversity of Phytophthora species in natural ecosystems and nurseries of Portugal: detrimental side effect of plant introductions from the age of discovery to modern globalizationPublication . Horta Jung, Marília; Maia, Cristiana; Mora-Sala, Beatriz; Abad-Campos, Paloma; Schena, Leonardo; Mosca, Saveria; Carella, Giuseppe; Moricca, Salvatore; Nechwatal, Jan; Dionísio, Lídia; Cravador, Alfredo; Jung, ThomasBetween 2010 and 2015, an extensive survey of Phytophthora diversity was performed across Portugal. Baiting and direct isolation tests obtained 48 Phytophthora taxa in 62 of 70 forest stands (89%) from 148 of 302 rhizosphere soil samples (49%) and 25 of 29 tree species (86%), and from bark cankers of Alnus lusitanica and Fagus sylvatica ; from 33 of 34 rivers and forest streams (97%); and in 12 of 13 forest nurseries (92%) from 54 of 87 root ball samples (61%) and 16 of 21 tree species (76%). The 799 Phytophthora isolates belonged to 28 known and three recently described species; one designated and two new non‐hybrid taxa; and five designated and nine new hybrid taxa. The majority, 34 Phytophthora taxa (71%), are introduced aliens in Europe while nine (19%) and five (10%) taxa are of cryptic and native origin, respectively. Phytophthora cinnamomi was the most common species in forests (56%) and forest nurseries (61%). Multiple first records for Portugal and partly Europe of both Phytophthora taxa and tree declines and new host– Phytophthora associations were found. Isolation rates from forest soil differed considerably between declining (65%) and healthy trees (10%), regardless of the tree species. The widespread infestations of nurseries with aggressive wide‐host range pathogens like P . cinnamomi , P . pseudocryptogea , P . × cambivora , P . multivora and P . plurivora , and host‐specific pathogens like P . alticola , P . quercetorum and P . quercina , will inevitably cause their further spread to the wider environment, exacerbating pathogen threats to forest ecosystems and thus weakening their resilience to climatic extremes.
- Multiple new cryptic pathogenic Phytophthora species from Fagaceae forests in Austria, Italy and PortugalPublication . Jung, Thomas; Horta Jung, Marília; Cacciola, Santa Olga; Cech, Thomas; Bakonyi, Jozsef; Seress, Diana; Mosca, Saveria; Schena, Leonardo; Seddaiu, Salvatore; Pane, Antonella; Lio, Gaetano Magnano di San; Maia, Cristiana; Cravador, Alfredo; Franceschini, Antonio; Scanu, BrunoDuring surveys of Phytophthora diversity in natural and semi-natural Fagaceae forests in Austria, Italy and Portugal, four new cryptic species were isolated from rhizosphere soil samples. Multigene phylogeny based on nuclear ITS, beta-tubulin and HSP90 and mitochondrial cox1 and NADH1 gene sequences demonstrated that two species, P. tyrrhenica and P. vulcanica spp. nov., belong to phylogenetic Clade 7a, while the other two species, P. castanetorum and P. tubulina spp. nov., clustered together with P. quercina forming a new clade, named here as Clade 12. All four new species are homothallic and have low optimum and maximum temperatures for growth and very slow growth rates at their respective optimum temperature. They differed from each other and from related species by a unique combination of morphological characters, cardinal temperatures, and growth rates. Pathogenicity of all Phytophthora species to the root system of their respective host species was demonstrated in soil infestation trials.