Phytophthora niederhauserii sp. nov., a new polyphagous species mostly isolated from ornamentals potted plants in twelve countries of five continents.

A non-papillate, heterothallic Phytophthoraspecies first isolated in 2001 and subsequently fromsymptomatic roots, crowns and stems of 33 plantspecies in 25 unrelated botanical families from 13countries is formally described here as a new species.Symptoms on various hosts included crown and stemrot, chlorosis, wilting, leaf blight, cankers andgumming. This species was isolated from Australia,Hungary, Israel, Italy, Japan, the Netherlands, Norway,South Africa, Spain, Taiwan, Turkey, the UnitedKingdom and United States in association with shrubsand herbaceous ornamentals grown mainly in greenhouses.The most prevalent hosts are English ivy(Hedera helix) and Cistus (Cistus salvifolius). Theassociation of the species with acorn banksia (Banksiaprionotes) plants in natural ecosystems in Australia, inaffected vineyards (Vitis vinifera) in South Africa andalmond (Prunus dulcis) trees in Spain and Turkey inaddition to infection of shrubs and herbaceousornamentals in a broad range of unrelated familiesare a sign of a wide ecological adaptation of thespecies and its potential threat to agricultural andnatural ecosystems. The morphology of the persistentnon-papillate ellipsoid sporangia, unique toruloidlobate hyphal swellings and amphigynous antheridiadoes not match any of the described species.Phylogenetic analysis based on sequences of the ITSrDNA, EF-1a, and b-tub supported that this organismis a hitherto unknown species. It is closely related tospecies in ITS clade 7b with the most closely relatedspecies being P. sojae. The name Phytophthoraniederhauserii has been used in previous studieswithout the formal description of the holotype. Thisname is validated in this manuscript with the formaldescription of Phytophthora niederhauserii Z.G. Abadet J.A. Abad, sp. nov. The name is coined to honor DrJohn S. Niederhauser, a notable plant pathologist andthe 1990 World Food Prize laureate.