Identification of two powdery mildew fungi, Oidium neolycopersici sp nov and O-lycopersici, infecting tomato in different parts of the world

A world-wide study of the Oidium species causing economic damage on tomato has identified two taxa using classical morphological, scanning electron mi croscope (SEM) and molecular phylogenetic analyses. The material consisted of a total of 25 tomato powdery mildew isolates and 29 herbarium specimens coming from all continents where tomatoes are grown. A taxon with non-caten ate conidia widespread in Europe, Africa. North and South America and Asia was identified as an O. subgen. Pseudoidium, species (teleomorph: Erysiphe sect. Erysiphe). Formerly mistaken for O. lycopersicum (or O. lycopersici), it is now recognised as a district species, O. neolycopersici sp. nov. A p hylogenetic analysis of the internal transcribed spacer (ITS) sequences of the ribosomal DNA (rDNA) indicated that O. neolycopersici is closely relate d to Erysiphe macleayae, E. aquilegiae and other Pseudoidium species. Only a taxon with catenate conidia was found on Australian specimens. This was i dentified as a species of O. subgen. Reticuloidium (teleomorph: Golovinomyc es sp.). Phylogenetic analysis of the rDNA ITS sequences showed that this s pecies is closely related to O. longipes infecting eggplant. Because it is most likely to be the same species as the original O. lycopersicum, which w as actually first described in Australia, this is here neotypified as O. ly copersici.