Identification by molecular techniques of phytoplasmas associated with apricot chlorotic leafroll in Italy

For a long time, aA severe disease has been observed on apricot in northern and southern Italy. The affected trees show symptoms similar to those of apricot chlorotic leafroll (ACLR), but include, in some cases, also early sprouting of leaves, production of malformed and abnormally small fruits, early autumnal leaf yellowing and premature leaf fall. The identification of phytoplasma(s) associated with this disease was carried out in different regions of Italy. The presence of phytoplasma specific DNA bands was detected in most of the symptomatic apricot samples after nested-PCR using the R16(X)F1/R1 primers that gave specific products for phytoplasma of group 16SrX. No amplification was obtained from the reaction mixture devoid of nucleic acid template and when the PCR products were reamplified with other specific primer pairs. Patterns obtained from RFLP of sequences amplified from apricot were indistinguishable from one another, identical with those of ACLR (16SrX-B) phytoplasma strain, and could be distinguished from those associated with apple proliferation (AP or 16SrX-A) and pear decline (PD or 16SrX-C). The results indicate that the disease outbreaks in different Italian regions are associated with strictly related phytoplasma strains. The spreading of the disease could be due to still unknown specific vectors or from the exchange of infected material.