Leafhoppers in phytoplasma infected carrot fields: species composition and potential phytoplasma vectors

Aster yellows phytoplasmas (‘Candidatus Phytoplasma asteris’, AY) have a wide host range and are transmitted in a persistent manner by phloem-feeding leafhoppers and planthoppers (Hemiptera: Auchenorrhyncha). Recently, aster yellows phytoplasmas have been reported for the first time in carrot fields in Serbia (Duduk et al., 2007). In order to find out potential vectors of identified phytoplasmas to carrots, and phytoplasmas occurring in infected insects, during 2007 and 2008 leafhoppers were collected and tested for the presence of phytoplasmas. The insects were trapped from the beginning of April to the end of October, in two sites in the South Bačka region of Serbia (Begeč and Begeč bogland), where phytoplasma associated diseases incidence was reported. Adult leafhoppers were sampled at two-week intervals, in carrot fields and weeds nearby, by using double-sided, yellow sticky traps (25x10) and by sweep netting in both sites. Leafhoppers were stored in 96% ethanol and identified before extraction of nucleic acids. Phytoplasma detection in identified insects was carried out by nested PCR-RFLP assays on 16S ribosomal gene. In the surveyed sites the presence of four known vectors of AY phytoplasmas was recorded: Anaceratagallia laevis (Ribaut), Macrosteles laevis (Ribaut), M. quadripunctulatus (Kirschbaum) and M. sexnotatus (Fallen) (Duduk at al., 2008). Other six leafhopper species, which are not known, according to literature as AY vectors but reported as vectors of other phytoplasmas and/or viruses, Anaceratagallia ribauti (Ossiannilsson), A. venosa (Fourcroy), Empoasca spp., Scaphoideus titanus (Ball), Psammotettix alienus (Dahlbom), P. striatus (Linnaeus) were identified. The other five identified species, Eupteryx mellissae (Curtis), Ophiola decumana (Kontkanen), Psammotettix confinis (Dahlbom), P. notatus (Melichar) and Errastanus ocellaris (Fallén), are not known in literature as vectors of any plant pathogen. AY phytoplasmas were detected in the following vector and non-vector leafhopper species: A. laevis, A. ribauti, M. quadripunctulatus, M. sexnotatus, O. decumana and P. confinis. Since the detection of AY phytoplasmas in previously unreported vector species is not a proof of their vector abilities, further research is needed to verify ability of A. ribauti, O. decumana and P. confinis to transmit AY phytoplasmas to carrot and to other phytoplasma host plants.