Recovery of Phytophthora species from potted ornamentals in commercial nurseries in Italy

During surveys of ornamental retail nurseries in Italy, Phytophthora species were recovered with a high frequency from roots of potted plants. Isolates obtained with BNPRAH and PARPNH selective media were identified using morphological criteria, electrophoretic patterns of mycelial proteins and isozymes and sequencing of internal transcribed spacer (ITS) region of rDNA. The species recovered most frequently from the roots and rhizosphere soil were P. nicotianae, P. palmivora, P. cryptogea and P. citricola. Other less common species were P. asparagi, P. cactorum, P. cinnamomi, P. drechsleri, P. gonapodyides, P. hedraiandra, P. inundata, P. niederhauseri, P. tentaculata and non identified Phytophthora spp.included in the ITS clades 1 and 6. Phytophthora isolates were obtained also from asymptomatic plants confirming the risk of spreading exotic and endemic pathogens through nursery stocks.