Characterization and mefenoxam sensitivity of Phytophthora spp. from ornamental plants in Italian nurseries

Abstract

Genetic variability and mefenoxam sensitivity are described for Phytophthora spp. isolates recovered from nine ornamental plant species at four locations in Sicily, Southern Italy. Fifty-four isolates of Phytophthora spp. were obtained from symptomatic plant tissues. Mating type analyses revealed that all isolates are heterothallic, consisting of mating type A1. Fungicide sensitivity assays determined that all isolates are sensitive to mefenoxam. Characterisation of 48 isolates was performed using molecular and phylogenetic analyses of the internal transcribed spacer of ribosomal DNA (rDNA-ITS), beta-tubulin (β-tub) and elongation factor 1 alpha (EF-1α) regions. The isolates belonged to Phytophthora nicotianae (34 isolates), P. arecae (syn. palmivora) (five) and P. niederhauserii (nine). The pathogenicity of three representative isolates was tested on seedlings or cuttings of each host, grown in a growth chamber. All isolates were pathogenic and reproduced symptoms identical to those observed in the nursery. This is the first report of disease caused by P. nicotianae, P. arecae or P. niederhauserii on several ornamental plants in Italy, and of the sensitivity of these Phytophthora species to mefenoxam.