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[EN] A non-papillate, heterothallic Phytophthora species first isolated in 2001 and subsequently from symptomatic roots, crowns and stems of 33 plant species in 25 unrelated botanical families from 13 countries is formally described here as a new species. Symptoms on various hosts included crown and stem rot, chlorosis, wilting, leaf blight, cankers and gumming. This species was isolated from Australia, Hungary, Israel, Italy, Japan, the Netherlands, Norway, South Africa, Spain, Taiwan, Turkey, the United Kingdom and United States in association with shrubs and herbaceous ornamentals grown mainly in greenhouses. The most prevalent hosts are English ivy (Hedera helix) and Cistus (Cistus salvifolius). The association of the species with acorn banksia (Banksia prionotes) plants in natural ecosystems in Australia, in affected vineyards (Vitis vinifera) in South Africa and almond (Prunus dulcis) trees in Spain and Turkey in addition to infection of shrubs and herbaceous ornamentals in a broad range of unrelated families are a sign of a wide ecological adaptation of the species and its potential threat to agricultural and natural ecosystems. The morphology of the persistent non-papillate ellipsoid sporangia, unique toruloid lobate hyphal swellings and amphigynous antheridia does not match any of the described species. Phylogenetic analysis based on sequences of the ITS rDNA, EF-1a, and b-tub supported that this organism is a hitherto unknown species. It is closely related to species in ITS clade 7b with the most closely related species being P. sojae. The name Phytophthora niederhauserii has been used in previous studies without the formal description of the holotype. This name is validated in this manuscript with the formal description of Phytophthora niederhauserii Z.G. Abad et J.A. Abad, sp. nov. The name is coined to honor Dr John S. Niederhauser, a notable plant pathologist and the 1990 World Food Prize laureate., We thank Dr Michael Coffey at the World Oomycete Genetic Resource (WOC) and World Phytophthora Genetic Resource (WPC) Collections for providing valuable information for this manuscript. We also thank Dr Elaine Davison at Western Australian Department of Agriculture for providing isolate VPRI 32086 to James H. Cunnington. The contribution of Dr Suzanne Spencer at the North Carolina Department of Agriculture and Consumer Services providing isolate PH2424 to Z. Gloria Abad is appreciated. Research in Hungary was supported by the Hungarian Scientific Research Fund (OTKA) grants K61107 and K101914. Research in Scotland was support by the Scottish government. Research in Italy was supported by Italian Ministry of University and Research (MIUR; PRIN 2008). LB is supported by the Swiss State Secretariat for Education and Research (grant reference: SER No. C09.0139) and the European Union for the projects ISEFOR ‘‘Increasing sustainability of European forests: modeling for security against invasive pests and pathogens under climate change (FP7- KBBE-2009-3 call, proposal number 245268) and the COST action FP0801 ‘‘Established and emerging Phytophthora: increasing threats to woodland and forest ecosystems in Europe’’.

Phylogenetic analysis of four species of Lundquistia revealed the genus to be polyphyletic. Morphological characters and phylogenetic relationships demonstrate that Lundquistia should be reduced to synonymy with Sporisorium. Three new combinations are proposed: Sporisorium dietelianum, S. duranii, and S. mexicanum. Sporisorium fasicularis is considered a synonym of S. panici-leucophaei.