Detection and molecular characterization of Phytophthora species in southern Italy

Polymerase chain reaction (PCR) assays were done on specimens collected in southern Italy from pepper and zucchini with Phytophthora blight; tomato with either late blight or buckeye rot; strawberry with crown rot, clementine (Citrus reticulata) with decline and root and fruit rot. All primers used were directed to nuclear ribosomal DNA (rDNA) sequences. The great majority of diseased plants and trees examined tested positive. Fungi were differentiated and characterised on the basis of primer specificity, restriction fragment length polymorphism (RFLP), and sequence analyses of the PCR-amplified rDNA. P. capsici was identified in diseased pepper and zucchini, P. infestans in tomato with late blight symptoms, P. nicotianae, P. cactorum and P. citrophthora in buckeye rot-affected tomatoes, diseased strawberries, and symptomatic Clementine trees, respectively. Thirty pure cultures of Phytophthora isolates from central and southern Italy, previously classified by traditional methods but never by molecular techniques, were also examined by RFLP and sequence analysis of PCR-amplified rDNA. The results of molecular identification tallied with those obtained by traditional methods for all but one isolate from lemon, formerly identified as P. hibernalis, which proved to be more closely related to P. citricola. Most of the diseases examined were already known in southern Italy but their causal agents had been characterised molecularly only from other geographic areas. It is worth mentioning that zucchini blight is a new record for southern Italy.