Molecular identification of phytoplasmas from olive trees in Italy

Olive trees (51 adult plants and 13 seedlings from different Italian regions) showing yellowing, shortening of internodes, witches' broom, bud abortion, little leaf, hypertrophied inflorescences, decline and fasciation symptoms were tested for the presence of phytoplasmas. DNAs extracted from leaf veins were amplified in reactions assisted by universal or group-specific primer pairs constructed on 16S rRNA phytoplasma sequences and analyzed by restriction with five different enzymes. Phytoplasmas, identified as members of 16Sr-IB, -V, and -XIIA groups (Lee et al., 1998) on the basis of their RFLP patterns, were detected from 34 samples (53.0%). Of these, 24 (ca 68.0%) carried a single phytoplasma [21 members of subgroup IB (87.5 %), one (4.0%) XIIA, and two (ca 8.0%) V]. Seven samples (20.5%) carried two different organisms (IB and XIIA subgroups members) and 3 (ca 9.0%) carried phytoplasmas of all three subgroups here identified. In addition, a IB subgroup member was detected in one symptomless adult tree. It appears that these phytoplasmas are ubiquitous in the areas surveyed, but a clear correlation between a given syndrome and the presence of one or more phytoplasmas did not emerge.