PROPAGATION OF FLAVESCENCE DOREE MLO (MYCOPLASMA-LIKE ORGANISM) IN THE LEAFHOPPER VECTOR EUSCELIDIUS-VARIEGATUS KBM

Flavescence doree (FD) MLO is experimentally maintained in broadbean and transmitted by the leafhopper vector Euscelidius variegatus. Indirect ELISA allowed the study, according to time after feeding access, of the distribution of MLO in the different organs of the vector. Colloidal gold indirect immunolabeling was used to visualize the MLO cells in the FD-infected organs. The alimentary tract was the first organ to become infected. Infected cells were not numerous but were crowded with MLO particles. Infection did not seem to be localized in specific cells. MLO multiplied in the cytoplasm of midgut cells and reached the hemolymph either by crossing between two cells or through individual infected cells. By circulating in the hemolymph, MLO infected salivary glands, in which they subsequently multiplied. Abdomen fat bodies and finally brain were infected; an increase in the number of MLO was observed in these organs. Observation by electron microscopy showed that MLO infection in fat bodies was important, with no particular localization. In contrast, MLO infection in the brain was low. Mycetomes were occasionally infected. No MLO particles were detected in malpighian tubules or in male and female genital organs. (C) 1994 Academic Press, Inc.