Characterisation of a 16SrII phytoplasma strain associated with bushy stunt of hawkweed oxtongue (Picris hieracioides) in south-eastern Serbia and the role of the leafhopper Neoaliturus fenestratus (Deltocephalinae) as a natural vector

Abstract

A 2-year study of host association, molecular characterisation and vector transmission of a phytoplasma related to the 16SrII group in a vineyard of south-eastern Serbia was conducted. Grapevine, eight common weeds and 31 Auchenorrhyncha species were collected and analysed for phytoplasma presence. PCR-RFLP analyses of the 16S rRNA gene identified the presence of a new strain of phytoplasma related to the 16SrII group in P. hieracioides with symptoms of stunting or bushy stunting. Grapevine samples, all without symptoms, were negative for phytoplasma presence. Plants of Erigeron annuus, Cynodon dactylon, Daucus carota and P. hieracioides, either exhibiting symptoms of yellowing or without symptoms, were positive for the presence of stolbur phytoplasma. Among the tested cicada species, seven were infected with phytoplasmas from the aster yellows group, two with stolbur phytoplasma, two with 16SrII phytoplasma, and one with the 16SrV-C phytoplasma subgroup. The phytoplasma strain of the 16SrII group was recorded in approximately 50 % of the collected leafhopper species Neoaliturus fenestratus and in a few specimens of the planthopper Dictyophara europaea. The vector status of N. fenestratus was tested using the second generation of the planthopper in two separate transmission trials with P. hieracioides and periwinkle seedlings. In both tests, the leafhopper successfully transmitted 16SrII phytoplasma to exposed plants, proving its role as a natural vector of this phytoplasma in Europe. A finer molecular characterisation and phylogenetic relatedness of the 16SrII phytoplasma strain by sequence analyses of the 16S rRNA and ribosomal protein genes rpl22-rps3 indicated that it was most closely related to the 16SrII-E subgroup.