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) sy mptomatic trees (two from Badajoz and two from Sevilla) was amplified by ne sted polymerase chain reaction (PCR) and directly sequenced. A sequence sim ilarity search against the EMBL and GenBank nucleotide databases showed tha t they were most similar to two previously sequenced isolates of pear decli ne phytoplasma of German and Italian origin. In a phylogenetic analysis the y clustered in a separate branch within the apple proliferation group. The four Spanish PD sequences were fully homologous to previously published pri mers R16F2n, primer forward (Ahrens and Seemuller. Phytopathology 82:828-83 2, 1992) and PD probe. However, primers fPD, fU5 and R16F2 showed some mism atches with these sequences.