IDENTIFICATION AND CHARACTERIZATION OF THE PHYTOPLASMA ASSOCIATED WITH ELM YELLOWS IN SOUTHERN ITALY AND ITS RELATEDNESS TO OTHER PHYTOPLASMAS OF THE ELM YELLOWS GROUP

In the neighbouring regions Basilicata, Campania, and Calabria of sout hern Italy, diseased trees of European field elm (Ulmus minor) were ex amined for phytoplasmal infection using polymerase chain reaction (PCR ) technology. All affected trees examined tested positively. Using a p rimer pair specific for the EY phytoplasma group and restriction fragm ent length polymorphism (RFLP) analysis of PCR-amplified ribosomal DNA , the organism detected was identified as the elm yellows (EY) phytopl asma. RFLP analysis of PCR-amplified ribosomal DNA was also employed t o attempt differentiation within the EY group which includes, in addit ion to the EY agent, phytoplasmas infecting Rubus, alder, eucalypts, S panish broom, and grapevine. Following separate digestion with AluI, R saI, Sau3AI, MseI, HhaI, and KpnI, all PCR-products from EY-group phyt oplasmas examined had similar RFLP profiles. When the same ribosomal D NA fragments were digested with TaqI restriction endonuclease, three d ifferent restriction profiles were detected among the EY-group phytopl asmas. These profiles represented, respectively, (1) the EY phytoplasm a (2) the phytoplasmas causing rubus stunt ana being associated with a lder yellows, spartium witches' broom, and eucalyptus little leaf, and (3) the flavescence doree phytoplasma. RFLP analysis using TaqI endon uclease enabled for the first time the differentiation of the phytopla smas associated with alder yellows, eucalyptus little leaf, and sparti um witches' broom from the EY agent.