Posters P-40 Microinjection and insect feeding medium bioassays to test the vector specificity of Flavescence dorée phytoplasma by some Hemiptera species

Phytoplasmas are a group mollicute plant pathogens transmitted by insect vectors in the Hemiptera. Although vector species have been identified for many of plant diseases associated with phytoplasmas, little is known about the specificity of vector transmission. Some phytoplasma strains seem to be specifically transmitted, for example phytoplasmas in the Elm yellow group seem to be transmitted by only a few leafhopper species. Other strains have low vector specificity, such as those clustered in the Aster yellows group, which are transmitted by several leafhopper species. Flavescence dorée of the grapevine is associated with a phytoplasma (FDP) that seems to be specifically transmitted in the field by the leafhopper vector Scaphoideus titanus Ball (Hemiptera, Cicadomorpha, Cicadellidae). However earlier works revealed that, in experimental conditions, other leafhopper species were alternative vectors of FDP to herbaceous hosts, i.e. Euscelidius variegatus Kirschbaum (Hemiptera, Cicadomorpha, Cicadellidae) (Caudwell et al. 1972). In the present work we studied the vector specificity of FDP by 15 Hemiptera Cicadomorpha and Fulgoromorpha species collected in European vineyards. To test vector transmission we adopted needle injection to deliver phytoplasma suspensions into the abdomen of candidate vector species (Purcell 1996), and after an incubation period we fed the injected insects on artificial diets through a Parafilm membrane (Zhang et al. 1998, Tanne et al. 2001) and tested the feeding medium for the presence of FDP DNA by a PCR procedure.