Four Spanish Isolates of Pear Decline Phytoplasma are Related to Other European Phytoplasmas of the Apple Proliferation Group

A portion of about 1000 bp within the 16S rDNA of four pear decline (PD) symptomatic trees (two from Badajoz and two from Sevilla) was ampli®ed by nested polymerase chain reaction (PCR) and directly sequenced. A sequence similarity search against the EMBL and GenBank nucleotide databases showed that they were most similar to two previously sequenced isolates of pear decline phytoplasma of German and Italian origin. In a phylogenetic analysis they clustered in a separate branch within the apple proliferation group. The four Spanish PD sequences were fully homologous to previously published primers R16F2n, primer forward (Ahrens and SeemuÈ ller. Phytopathology 82:828±832, 1992) and PD probe. However, primers fPD, fU5 and R16F2 showed some mismatches with these sequences.