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

Abstract

Flavescence dorCe (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 111, 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.

Immunodominant membrane proteins from two phytoplasmas in the aster yellows clade (chlorante aster yellows and clover phyllody) are highly divergent in the major hydrophilic region The GenBank accession numbers for the sequences reported in this paper are AF244540 and AF244541 for AY-C and CP, respectively.

“…Preliminary evidence for one phytoplasma, the grapevine pathogen flavescence dore! e, suggests that some unidentified pathogen-specific material in phytoplasmaenriched preparations will bind to insect cells (Lefol et al, 1993). Phytoplasma classification is currently based mainly on 16S rRNA gene sequences (Seemu$ ller et al, 1998).…”

Risk of a spreading a dangerous new grapevine disease, Flavescence dorée (FD) phytoplasma, and the distribution of its leafhopper vector (Scaphoideus titanus Ball) in Hungary

“…Ennek azonban egyelôre nem kell különös jelentôséget tulajdonítanunk, mert az még további vizsgálatokat igényel, hogy ez a növényfaj bármilyen szerepet töltene be a Flavescence dorée fitoplazma epidemiológi-ájában (Carraro 2005). Lefol et al (1993) laboratóriumi kísérletekben képes volt több más rovart is megfertôzni ezzel a fitoplazmával (a növénypatogén fitoplazmák a rovarokban betegséget nem okoznak, még ha nyálmirigyeikben elszaporodnak is! ), de azt nem voltak képesek igazolni, hogy ezek vektorként mûködnének a szabadban.…”

“…Ezután hosszú lappangási idôszak következik, melynek során még nem képes a kórokozót terjeszteni, mert ez az idô szükséges a kórokozó elszaporodásához a rovar nyálmirigyeiben (Lefol et al 1993). A látens idôszak mintegy 38-42 nap, aminek elmúltával a rovar élete végéig terjeszteni fogja a kórokozót.…”

Scientific Opinion on pest categorisation of Grapevine Flavescence dorée

“…Then it colonises the haemolymph before entering and multiplying in the salivary gland. Finally it is delivered to another host plant through saliva (Lefol et al, 1993(Lefol et al, , 1994. There is a temperature-dependent latency period between the phytoplasma's acquisition by the insect and its transmission to another host plant, between 10 and 45 days.…”