Survey for grapevine yellows phytoplasmas in diverse European countries and Israel

Research NotePhytoplasmas of a large number of GY-affected grapevines from several European countries and Israel were characterized using PCR-RFLP of a 16S rDNA region. Only phytoplasmas in the EY group and the stolbur group were found. The latter was the most wideley spread

Le syndrome des basses richesses de la betterave sucrière en Bourgogne, un modèle de maladies infectieuses émergentes - Bilan des recherches 1997-2007

National audienceUne maladie inconnue de la betterave sucrière est apparue en Côte d'Or au début des années 1990 et a gagné le reste du bassin sucrier du Centre-est (Bourgogne et Jura). Les programmes d'étude financés par la filière betterave-sucre et Conseil régional de Bourgogne de 1997 à 2007, ont permis d'en élucider entièrement l'étiologie et la transmission, de développer des méthodes de diagnostic moléculaire, et de parvenir à une compréhension globale de son épidémiologie. Les méthodes de lutte directes et agronomiques préconisées ont montré leur efficacité pour limiter les pertes de rendement en sucre associées à cette maladie. Par ailleurs, la biologie de bactéries pathogènes habitant le phloème des plantes, encore peu connues, a été étudiée dans leurs relations complexes avec leur insecte vecteur, permettant des hypothèses sur les mécanismes d'émergence de ce type de nouvelles maladies des plantes

Syndrome des basses richesses de la betterave sucrière, caractérisation de la protéobactérie associée, biologie et vection (perspectives de lutte)

Le syndrome des basses richesses (SBR) est une maladie de la betterave sucrière en Bourgogne et en Franche-Comté. La SBRp, une nouvelle gamma-3 protéobactérie phytopathogène, proche de bactéries endosymbiotiques secondaires des hémiptères est l agent étiologique majoritaire. Pentastiridius leporinus (Hemiptera, Cixiidae) est le vecteur principal du SBR. Son éthologie et son cycle monovoltin se sont adaptés à la rotation culturale betterave sucrière - céréale. C est majoritairement durant sa phase adulte qu il transmet avec une grande efficacité le SBR. Pentastiridius leporinus acquiert la SBRp par voie maternelle et par prise de nourriture à l état larvaire sur pivots de betteraves infectées et sur les débris de betteraves enfouies dans le sol. Il existe en champ un phénomène d entretien de populations fortement contaminées. Plus les adultes migrants sont nombreux et plus leur taux d'infection par la SBRp est élevé, plus le taux d'acquisition horizontale par les larves de la génération suivante, est important. L association d une lutte insecticide avec une lutte agronomique, permettrait de lutter efficacement contre le SBR.The Syndrome "basses richesses" (SBR) is a disease of sugar beet described in Bourgogne and Franche Comté. The SBRp, a new phytopathogenic gamma-3 proteobacteria, related to secondary endosymbiotic bacteria of hemipters is the major aetiological agent. Pentastiridius leporinus (Hemiptera, Cixiidae) is the principal vector of SBR.. Its ethology and monovoltine biological are fitted to the cultural rotation sugar beet cereals. Adults were the more efficient developmental stage for cycle transmission of SBR. Pentastiridius leporinus acquired SBRp vertically through the egg, and also through feeding acquisition by nymphs on infected tap roots of sugar beet and on fragments of sugar beets left deep in the ground. Hence a process could be described that results in maintaining field populations with a high rate of infection. The more numerous were migrating adult populations and the higher was their SBRp infection rate, the higher was the rate of horizontal acquisition by nymphs of the next generation. The association of insecticide control with cultural practice would permit an efficient control of SBR.DIJON-BU Sciences Economie (212312102) / SudocSudocFranceF

nfluence of phytoplasma-insect vectors-host plants interactions on the epidemiology of Flavescence dorée of the grapevine disease

Ecological-biological interactions of Flavescence dorée phytoplasma (FDP), host plants and vectors were investigated in field and laboratory conditions. Main results showed that (i) FDP reduced the fitness of its natural vector Scaphoideus titanus Ball and of the experimental vector Euscelidius variegatus Kirschbaum, congenital infection in S. titanus offspring did not occur; (ii) FDP-affected tolerant grapevine cultivar Merlot was shown to be a poorer source of FDP for S. titanus acquisition than the susceptible grapevine cultivar White Pinot; (iii) a statistical model describing the pattern of infected and infective S. titanus occurrence in the vineyards was proposed on the basis of experimental data of a 4-year survey of the leafhopper species populations collected in severely FDP-affected vineyards; (iiii) results of assays of insect injection and artificial feeding suggested that vector specificity of FDP is restricted to the Cicadellidae family, subfamily Deltocephalinae.Les interactions biologiques et écologiques entre le phytoplasme de la Flavescence dorée (FDP), les plantes hôtes et les vecteurs ont été étudiés au champ et au laboratoire. Les résultats principaux montrent que (i) le FDP réduit les performances de son vecteur naturel, Scaphoideus titanus Ball et du vecteur expérimental Euscelidius variegatus Kirschbaum; (ii) les plantes infectées du cépage tolérant Merlot constituent un réservoir moins important que le cépage sensible Pinot Blanc pour l'acquisition du FDP par S. titanus; (iii) un modèle statistique qui décrit l'évolution des cicadelles S. titanus infectées et infectieuses a été proposé sur la base de données expérimentales acquises pendant une étude de 4 années sur des populations du vecteur dans des vignobles très affectés par FDP; (iiii) la microinjection d'extraits enrichis en FDP et des tests de prise de nourriture artificielle sur membrane suggèrent que la spécificité de vection du FDP est limitée aux insectes de la famille des Cicadellidae, sous-famille Deltocephalinae.DIJON-BU Sciences Economie (212312102) / SudocSudocFranceF

Host preferences of the leafhopperScaphoideus titanus, vector of “flavescence dorée” phytoplasma

International audienceThe spread of “flavescence dorée” (FD) phytoplasma among grapevines is made by the leafhopper Scaphoideus titanus (Hemiptera: Cicadellidae). Laboratory choice tests were performed to better understand insect vector preferences. The host preferences of nymphs and adults were compared between an experimental host plant, broadbean, and its natural host plant, grapevine, and between healthy and FD-infected plants. Grapevine was preferred to broadbean by nymphs and adults, but this preference was influenced by feeding experience. The presence of FD phytoplasma in plants made FD-infected grapevines more attractive than the healthy ones to both instar stages tested, while the preference for infected broadbean over healthy ones was only observed in adults. Plant yellowing due to the phytoplasma may increase the attractiveness of FD-infected plants. The experimental results showed that S. titanus was more attracted to yellow cues than to green, blue, or red ones. The attractiveness of FD-infected grapevines to the vector could be an efficient way to enhance disease spreading by increasing the proportion of infective vectors in the population

Spatio-temporal pattern of Pentastiridius leporinus migration in an ephemeral cropping system

International audience* 1 Cixiid planthoppers (Hemiptera: Fulgoromorpha: Cixiidae) are considered to be important economic pests because of their ability to transmit phloem-restricted prokaryotes causing emerging plant diseases worldwide. However, little information is available on the biology and ecology of such species. This is the case for Pentastiridius leporinus (Linnaeus), a cixiid planthopper reported to live on common reed across Countries of Central and Northern Europe. However, in the east of France, the same planthopper species appears to complete its life cycle in the sugar beet-wheat cropping system and has been repeatedly shown to transmit prokaryotic plant pathogens that are associated with an emerging disease of sugar beet called syndrome ‘basses richesses'. * 2 To gather evidence on the biology of the planthopper in the cropping rotation, we analysed the flight activity of adults. We used transparent sticky traps for sampling migrating adults and quantified nymphs as well as emerging adults on the roots of wheat plants. * 3 Results showed a significant correlation between disappearance of nymphs and emerging adults from wheat roots and the occurrence of migrant adults in nearby sugar beet fields. Planthoppers migrated more abundantly and colonized sugar beet for longer periods than any other crop available. Flight activity was very pronounced during the migratory phase that was extended from the middle of June to the middle of July. A geographic information system and geostatical analysis revealed that planthoppers flew and colonized the centre of the sugar beet field rather than the borders. * 4 Overall, results obtained in the present study suggest that the ecology and biology of the planthopper vector in the cropping rotation is a primary factor that leads to the emergence of the syndrome ‘basses richesses' disease of sugar beet

Insect Vectors (Hemiptera: Cixiidae) and Pathogens Associated with the Disease Syndrome “Basses Richesses” of Sugar Beet in France

International audienceThe syndrome “basses richesses” (SBR) is a disease of sugar beet in eastern France associated with two phloem-restricted, nonculturable plant pathogens: a stolbur phytoplasma and a γ-3 proteobacterium, here called SBR bacterium. Three planthopper (Hemiptera: Cixiidae) species were found to live near and within sugar beet fields in eastern France: Cixius wagneri, Hyalesthes obsoletus, and Pentastiridius leporinus. The role of these planthoppers in spreading the two pathogens to sugar beet was studied. Based on its abundance and high frequency of infection with the SBR bacterium, P. leporinus was considered to be the economic vector of SBR disease. C. wagneri, the primary vector of ‘Candidatus Phlomobacter fragariae’ to strawberry in western France, also was found to be infected by the SBR bacterium and to transmit the pathogen to sugar beet. Neither C. wagneri nor P. leporinus were infected by stolbur phytoplasma. Populations of H. obsoletus living on bindweed (Convolvulus arvensis) and nettle (Urtica dioica) collected near sugar beet fields did not carry the SBR bacterium, but were highly infected with two restriction fragment length polymorphism-differentiable stolbur phytoplasma isolates. In transmission assays, only the bindweed phytoplasma isolate was transmissible to and pathogenic on sugar beet. When compared with controls, the bindweed stolbur phytoplasma and SBR bacterium similarly reduced the biomass of sugar beet plants, but the phytoplasma caused greater reductions in taproot biomass and sugar content than the SBR bacterium

Characterization and evolution of two bacteriome-inhabiting symbionts in cixiid planthoppers (Hemiptera: Fulgoromorpha: Pentastirini)

International audienceLike other plant sap-sucking insects, planthoppers within the family Cixiidae (Insecta: Hemiptera: Fulgoromorpha) host a diversified microbiota. We report the identification and first molecular characterization of symbiotic bacteria in cixiid planthoppers (tribe: Pentastirini). Using universal eubacterial primers we first screened the eubacterial 16S rRNA sequences in Pentastiridius leporinus (Linnaeus) with PCR amplification, cloning, and restriction fragment analysis. We identified three main 16S rRNA sequences that corresponded to a Wolbachia bacterium, a plant pathogenic bacterium, and a novel gammaproteobacterial symbiont. A fourth bacterial species affiliated with ‘Candidatus Sulcia muelleri’ was detected in PCR assays using primers specific for the Bacteroidetes. Within females of two selected cixiid planthoppers, P. leporinus and Oliarus filicicola, fluorescence In situ hybridization analysis and transmission electron microscopy observations showed that ‘Ca. Sulcia muelleri’ and the novel gammaproteobacterial symbiont were housed in separate bacteriomes. Phylogenetic analysis revealed that both of these symbionts occurred in at least four insect genera within the tribe Pentastirini. ‘Candidatus Purcelliella pentastirinorum’ was proposed as the novel gammaproteobacterial symbiont

Vector Transmission of a Plant-Pathogenic Bacterium in the Arsenophonus Clade Sharing Ecological Traits with Facultative Insect Endosymbionts

International audienceThe planthopper Pentastiridius leporinus (Hemiptera: Cixiidae) is the major vector of a nonculturable plant-pathogenic γ-3 proteobacterium associated with a disease of sugar beet called syndrome basses richesses (SBR). The bacterium, here called SBR bacterium, belongs to the Arsenophonous clade, which includes mostly insect-associated facultative symbionts. Assays using field-collected planthopper nymphs and adults were carried out to investigate the interaction of SBR bacterium with the insect vector and its transmission to sugar beet. Field-collected planthoppers showed a percentage of infection that averaged from 57% for early instar nymphs to near 100% for late instar nymphs and emerging adults. SBR bacterium was persistently transmitted by emerging adults. Root-feeding nymphs were able to inoculate SBR bacterium to sugar beet. The bacterium was transmitted vertically from infected parental females to their respective offspring with an average frequency of 30%. Real-time polymerase chain reaction assays on dissected planthopper internal organs revealed a high concentration of the bacterium within male and female reproductive organs and within female salivary glands. SBR-like bacteria were observed through transmission electron microscopy in the cytoplasm of different insect organs including ovaries, salivary glands, and guts with no evidence for cytological disorders. SBR bacterium seems to share common ecological traits of insect-transmitted plant pathogens and facultative insect endosymbionts suggesting it may have evolved primarily as an insect-associated bacterium

Monitoring of grapevine leafroll-associated virus 1 (GLRaV-1) dispersion by the mealybug phenaccocus aceris

International audienceA four-year monitoring in a vineyard affected with leafroll and first transmission experiments were performed in order to understand leafroll dispersion by the mealybug Phenacoccus aceris. Our data showed for the first time that GLRaV-1 progression was due to the colonisation of the monitored vineyard by infective P. aceris spreading from bordering infected vineyards. Additionally, GLRaV-3 and Grapevine virus A (GVA) were transmitted by first instar nymphs of P. aceris