Phylogenetic data for the description of Phytophthora heterospora sp. nov.

<p>Since 1999, an unusual <i>Phytophthora</i> species has repeatedly been found associated with stem lesions, root and collar rot on young olive trees in Southern Italy. In all cases, this species was obtained from new commercial plantations or from nursery seedlings. Morphologically the <i>Phytophthora</i> isolates were characterized by the abundant production of caducous conidia and sporangia, resembling <i>P. palmivora</i> var. <i>heterocystica</i>. Additional isolates with similar features were obtained from nursery plants of <i>Ziziphus spina-christi</i> in Iran, <i>Juniperus oxycedrus</i> and <i>Capparis spinosa</i> in Italy, and mature trees in commercial farms of <i>Durio zibethinus</i> in Vietnam. In this study, morphology, breeding system and growth characteristics of these unusual <i>Phytophthora</i> isolates were examined, and a combined mitochondrial and nuclear multigene phylogenetic analysis was performed. The proportion between conidia and sporangia varied amongst isolates and depending on the availability of free water. Oogonia with amphigynous antheridia and aplerotic oospores were produced in dual cultures with an A2 mating type strain of <i>P. palmivora</i> indicating all isolates belonged to the A1 mating type. Phylogenetically, these isolates grouped in a distinct well-supported clade sister to <i>P. palmivora</i>, indicating they constitute a separate species. The new species, described here as <i>Phytophthora heterospora</i> sp. nov., proved to be highly pathogenic to both olive and durian plants in artificial stem inoculations.</p>