Diversity of phytoplasmas identified in the polyphagous leafhopper Euscelis incisus (Cicadellidae, Deltocephalinae) in Serbia: pathogen inventory, epidemiological significance and vectoring potential

Abstract

Euscelis incisus is polyphagous leafhopper that is widely distributed and abundant in diverse agroecosystems. Two generations per year allows this species to come into contact with a plethora of different phytoplasmas. We first investigated the interactions of E. incisus with phytoplasmas in different ecosystems as a bioindicator of phytoplasma diversity. Among the 510 analyzed E. incisus specimens collected from eight localities in Serbia, 53 (10%) tested positive for diverse ‘Ca. Phytoplasma’ taxa. Restriction fragment length polymorphism (RFLP) analysis and sequence comparison based on the F2nR2 fragment of the 16S rRNA gene revealed the presence of six 16S phytoplasma ribosomal groups and eight subgroups in E. incisus (16SrI-R, 16SrI-F, 16SrII-E, 16SrIII-B, 16SrIX-C, 16SrIX-E, 16SrXI-G and 16SrXII-A). The most prevalent was the 16SrXII-A phytoplasma group, represented by two multilocus stolbur phytoplasma genotypes: STOLg and Rqg31g. While the 16SrXII-A phytoplasmas were identical to the previously recorded isolates from Serbia, the 16SrI-F and 16SrI-R subgroups closely related to the previously documented 16SrI-B and 16SrI-C subgroups were recorded for the first time in Serbia. In addition, records of the 16SrIX and 16SrXI groups represent the first findings of these phytoplasma groups in Serbia. Transmission trials of ‘Ca. P. solani’ were performed with naturally infected E. incisus adults. The leafhoppers successfully transmitted stolbur phytoplasma to exposed Catharanthus roseus plants, indicating their role as a natural vector.