Phytoplasma detection in Empoasca decedens Paoli and Empoasca spp. and their possible role as vectors of European stone fruit yellows (16SrX-B) phytoplasma

After first identification of 16SrX-B phytoplasma sub-group (European Stone Fruit Yellows: ESFY) in Empoasca decedens P. and in Empoasca spp. collected in an apricot-plum experimental orchard in June 2001 and in January 2002, further field surveys, together with transmission trials, were carried out to verify the ability of E. decedens to transmit ESFY from Prunus armeniaca L. to P. armeniaca. In the experiment performed on July 2001, it was possible to identify ESFY presence ten months after inoculation; in the trial taken up on July 2002, the phytoplasma was detectable fifty-one days after inoculation. Yellow sticky traps were placed and kept out weekly since June 2002 to January 2003 in the two orchards of Istituto Sperimentale per la Frutticoltura (ISF) in Southern and in Central-Italy. During all the research E. decedens and Empoasca spp. were found on the traps, however insects positive to ESFY were found, in the Southern field, in July, October and January and, in the Central-one, in September, October and November. After extraction of nucleic acids with a chloropform/phenol procedure, two nested–PCR reactions, with primers amplifying general and group specific ribosomal sequences, were carried out on batches containing two to seven insects and in plant employed in transmission experiments. Restriction fragment length polymorphism (RFLP) analyses, mainly with TruI, Tsp509I, RsaI and SspI were employed for phytoplasma identification. Numerous samples of E. decedens and Empoasca spp. showed the presence of ESFY (16SrX-B) phytoplasma. In other samples of E. decedens P. and Empoasca spp. different phytoplasma groups were identified