ATTACHMENT OF THE FLAVESCENCE DOREE PATHOGEN (MLO) TO LEAFHOPPER VECTORS AND OTHER INSECTS

Flavescence doree (FD) is an important yellows disease of grapevine, c aused by mycoplasma-like-organism (MLO) and is transmitted in the fiel d by the leafhopper Scaphoideus titanus Ball. It can be transmitted in the laboratory between Vicia faba test plants by the leafhopper, Eusc elidius variegatus Kbm. A technique to identify a specific attachment system between the MLO and the leafhopper vectors was developed. In th is method, called ''Double Dot'', extracts of macerated healthy whole insects or organs applied to a support membrane or cryosections of hea lthy whole leafhoppers, are incubated with a MLO-enriched extract from FD-infected V. faba or FD-infected E. variegatus. Attached MLO cells were identified by immunolabelling using FD-MLO specific monoclonal an tibodies. Attachment of MLO cells was obtained on extracts of healthy S. titanus and E. variegatus and on tissues such as salivary glands, h emolymph and alimentary tract. On cryosections, MLO attachment was obt ained on acini IV and V of the salivary glands and on some acini III, on the ventriculus of the alimentary tract, and on the abdomen fat bod ies. ''Double dot'' experiments were done using other insect species, and MLO cells attachment was obtained on most MLO-vector insects but a lso on insects from a few non-vector species.