Attachment of the Flavescence doree pathogen (MLO) to leafhopper vectors and other insects

Abstract

SUMMARY Flavescence doree (FD) is an important yellows disease of grapevine, caused by mycoplasma‐like‐organism (MLO) and is transmitted in the field by the leafhopper Scaphoideus titanus Ball. It can be transmitted in the laboratory between Vicia faba test plants by the leafhopper, Euscelidius variegatus Kbm. A technique to identify a specific attachment system between the MLO and the leafhopper vectors was developed. In this method, called “Double Dot”, extracts of macerated healthy whole insects or organs applied to a support membrane or cryosections of healthy 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 antibodies. Attachment of MLO cells was obtained on extracts of healthy S. titanus and E. variegatus and on tissues such as salivary glands, hemolymph and alimentary tract. On cryosections, MLO attachment was obtained 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 bodies. “Double dot” experiments were done using other insect species, and MLO cells attachment was obtained on most MLO‐vector insects but also on insects from a few non‐vector species.