The first Stolbur Phytoplasma occurrence on two St. John's Worth species (Hypericum perforatum L. and Hypericum barbatum L.) in Serbia

The symptoms indicating phytoplasma like leaf yellowing, reddening and early drying were observed on two St. John’s worth species (Hypericum perforatum L. and Hypericum barbatum L.) on infected fields (Pancevo, Indjija and Stara Pazova) in Serbia in 2008. Electron microscopy examination of the ultra-thin sections revealed the presence of numerous polymorphic phytoplasma-like bodies in the phloem tissue of leaf midribs and petioles. The phytoplasma etiology was confirmed by polymerase chain reaction (PCR) using 3 sets of primers (P1/P7, P1/16S-Sr and R16F2n/R16R2). Restriction fragment length polymorphism (RFLP) analysis of amplification products of 1.2 kb (obtained with R16F2n/R2 primer pair) in 51 from 60 symptomatic plants, indicated the presence of 16SrXII-A phytoplasma subgroup from all three affected localities. Sequence of R16F2n/R2 amplicon for representative phytoplasma H. perforatum L. isolate Hp22 was deposited in the GeneBank with accession number JQ033928. This is the first report of the natural occurrence of Stolbur phytoplasma in two cultivated St. John’s worth species in Serbia