Individuazione di ‘Candidatus phytoplasma ziziphi’ in drupacee in Italia.

During the last years in two different areas of northern Italy in which cherry and peach trees are mainly grown it was observed a severe symptomatology that leads plants to decline and die in two-weeks/one month maximum. From the beginning of the summer the affected plants show leaves of smaller size, with chlorosis, reddening, curling aspect, and premature fall; young branches also show some lack of lignifications. Preliminary tests allow to exclude the presence of several biotic or abiotic agents therefore to verify the possible phytoplasma association with the disease, nucleic acid extraction was performed from leaf midribs as well as from phloem scrapes of declining trees. Chloroform/phenol extraction (Prince et al., 1993) was applied before molecular analyses that were then carried out by nested PCR with primers amplifying 16S rDNA, spacer region and part of the 23S region. Samples positive with R16RF2/R2 primers were subjected to RFLP analyses with MseI, RsaI, and HpaII (Lee et al., 1998), restriction profiles obtained from peach and cherry samples were undistinguishable from each others and were identical to the reference sample JWB (jujube witches’ broom) employed as control, therefore the phytoplasmas detected were attributed to ribosomal subgroup 16SrV-B. The further use of CJF1/R1 (Zhu et al., 1977) subgroup 16SrV-B specific primers allow to confirm this identification. Sequencing of R16F2/R2 amplicons obtained from one sample of peach and one of cherry respectively was also performed. After aligning and comparing these sequences with those in GenBank it was possible to determine the presence of 99% homology with sequence AB052877, Candidatus Phytoplasma ziziphi recently described (Jung et al., 2003). It is know from literature that in areas where peach and cherry are mainly cultivated severe phytoplasma diseases often occur, but they are associated with diverse agents: 16SrX-B in Europe, 16SrIII-A in Canada and California, 16rVII-A in Sicily, 16SrV-B in India and China, 16SrXII-A in Italy and Chile. The detection of jujube witches’ broom subgroup phytoplasmas is however reported for the first time in Italy and this must to be taken into consideration for possible epidemic outbreaks. It is important to continue the monitoring at national level in order to verify the real diffusion and spreading of this phytoplasma in Italian cultivations.