Species of the genus Geosmithia are associated with insect species, mainly bark beetles. On Ulmus spp., the same beetles are also vectors of Ophiostoma ulmi s.l., the agent of Dutch elm disease (DED), a worldwide elm disease. Aim of this paper is to characterise Geosmithia species associated with elms and/or elm beetles in Europe. Seventy-two strains representative of all morphological taxonomic units were used to build a phylogenetic tree based on ITS, β-tubulin and elongation factor 1-α gene regions. On the basis of molecular and morpho-physiological traits, seven taxonomic entities were identified. In addition to the species previously known our results assigned strains previously identified as Geosmithia pallida to two separate taxa: Geosmithia sp. 2 and Geosmithia sp. 5. Two new species, Geosmithia omnicola and Geosmithia ulmacea, are described. Two strains were assigned to the partially described species Geosmithia sp. 20. Geosmithia species living on Ulmus do not discriminate between elm species, but between different environments. The association between Ulmus and Geosmithia is common, stable, and seems to be related to specific vectors. The relationship between Geosmithia and Ophiostoma would deserve further investigation, as these fungi share the same vectors and habitat for a significant part of their life cycles.

Department for Innovation in Biological Agro food and Forest Systems University of Tuscia via San Camillo de Lellis s n c 01100 Viterbo Italy

Department of Biology University of Florence via Madonna del Piano 6 50019 Sesto Fiorentino Italy

Department of Botany Faculty of Science Charles University Benatská 2 128 01 Praha 2 Czech Republic

Institute for Sustainable Plant Protection C N R via Madonna del Piano 10 50019 Sesto Fiorentino Italy

Institute of Microbiology of the Academy of Sciences of the Czech Republic v v i Videnská 1083 142 20 Praha 4 Czech Republic

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