Development of an in vitro Dual Culture System for Grapevine and Xiphinema index as a Tool for Virus Transmission

Grapevine fanleaf virus (GFLV) is a nepovirus that is transmitted to grapevines by the ectoparasitic nematodeXiphinema index. GFLV causes severe losses in yield and quality in viticulture worldwide. Presently, laborious andtime-consuming field trials or greenhouse tests are necessary for screening putative GFLV resistance in new grapegenotypes developed in breeding programmes. We developed an in vitro dual culture system for grapevines andnematode vectors that requires less time and space than inoculation experiments done in the greenhouse. Virusinfection of in vitro grapevines was investigated using immunocapture-reverse transcriptase-polymerase chainreaction (IC-RT-PCR) analysis. The development of root galls induced by feeding nematodes on in vitro grapevineswas also analysed. Virus infection in grapevines in the dual culture with viruliferous nematodes was detected sixweeks post-inoculation. Root galls were always absent from parasitised in vitro grapevines with detectable virusinfection, whereas they developed on some parasitised, but virus-negative tested grapevines. Therefore, root gallscannot be used as a reliable indicator for parasitism and virus transmission

Analysis of the acquisition and multiplication efficiency of different strains of Ca. Phytoplasma mali by the vector Cacopsylla picta

Based on previous observations during long-term acquisition and transmission trials, studies were carried out under standardized conditions in order to analyse the acquisition and multiplication efficiencies of different strains of Candidatus Phytoplasma mali by different developmental stages of Cacopsylla picta. The acquisition of Ca. P. mali from micropropagated plants infected with different strains was tested for nymphs, larval stages and new adults of C. picta. When born on infected plants a nearly 100% acquisition was achieved for all strains of Ca. P. mali by C. picta. Differences in acquisition efficiency were observed for new generation adults which acquired the phytoplasma as imagines. The multiplication efficiency of the different Ca. P. mali strains inside the insects was analysed by quantitative real-time PCR. Significant differences in the capacity of the different strains to colonise the insect were found. Despite high acquisition rates only few subsequent transmission events to healthy test plants could be recorded

Influence of Apple stem grooving virus on Malus sieboldii-derived apple proliferation resistant rootstocks

Apple stem grooving virus (ASGV, Capillovirus) is widely spread in apple growing regions. As it causes no symptoms on most cultivated apple varieties and rootstocks it is considered latent in Malus x domestica. In Asia, however, ASGV has been found associated with topworking disease of apple rootstocks originating from Malus sieboldii. Recently, M. sieboldii and its hybrids have gained new interest in Europe as they confer resistance to apple proliferation (AP) disease. A new breeding program aiming to develop AP-resistant rootstocks of agronomic value for modern apple culture, reported unexpected tree decline which was to be associated with ASGV. As little information is available on the variability of ASGV isolates in Germany, the complete genome of a German isolate of ASGV associated with tree decline was cloned and sequenced. Sequence comparisons with available ASGV isolates revealed two regions of high variability in the genome. The genetic variability of additional isolates from Germany and other countries were collected and the variable areas characterised. In addition ASGV was successfully maintained in micropropagated apple trees and could be transmitted by in vitro grafting to various genotypes, making it possible to study in vitro the effect of the virus and virus/phytoplama combination on M. sieboldii-derived genotypes. Keywords: Latent apple viruses, Candidatus Phytoplasma mali, micropropagation, in vitro grafting, genetic variabilit

Genomeditierung von Pflanzen im internationalen und rechtlichen Kontext

Das Urteil des Europäischen Gerichtshofs (EuGH) vom Juli 2018 und die damit verbundenen Auflagen für die Zulassung Genom-editierter Pflanzen machen die Nutzung entsprechender Verfahren für die Pflanzenzüchtung in Europa nahezu unmöglich. Unser Mitglied, die Gesellschaft für Pflanzenbiotechnologie, begleitet diese Entwicklungen mit großer Sorge. Hier stellt sie sich und ihre Arbeit vor

Factors associated with diversity, quantity and zoonotic potential of ectoparasites on urban mice and voles

Wild rodents are important hosts for tick larvae but co-infestations with other mites and insects are largely neglected. Small rodents were trapped at four study sites in Berlin, Germany, to quantify their ectoparasite diversity. Host-specific, spatial and temporal occurrence of ectoparasites was determined to assess their influence on direct and indirect zoonotic risk due to mice and voles in an urban agglomeration. Rodent-associated arthropods were diverse, including 63 species observed on six host species with an overall prevalence of 99%. The tick Ixodes ricinus was the most prevalent species, found on 56% of the rodents. The trapping location clearly affected the presence of different rodent species and, therefore, the occurrence of particular host-specific parasites. In Berlin, fewer temporary and periodic parasite species as well as non-parasitic species (fleas, chiggers and nidicolous Gamasina) were detected than reported from rural areas. In addition, abundance of parasites with low host-specificity (ticks, fleas and chiggers) apparently decreased with increasing landscape fragmentation associated with a gradient of urbanisation. In contrast, stationary ectoparasites, closely adapted to the rodent host, such as the fur mites Myobiidae and Listrophoridae, were most abundant at the two urban sites. A direct zoonotic risk of infection for people may only be posed by Nosopsyllus fasciatus fleas, which were prevalent even in the city centre. More importantly, peridomestic rodents clearly supported the life cycle of ticks in the city as hosts for their subadult stages. In addition to trapping location, season, host species, body condition and host sex, infestation with fleas, gamasid Laelapidae mites and prostigmatic Myobiidae mites were associated with significantly altered abundance of I. ricinus larvae on mice and voles. Whether this is caused by predation, grooming behaviour or interaction with the host immune system is unclear. The present study constitutes a basis to identify interactions and vector function of rodent-associated arthropods and their potential impact on zoonotic diseases

Size and sequence variability of the arabis mosaic virus protein 2 A

International audienc

Size and sequence variability of the arabis mosaic virus protein 2A

International audience The RNA 2 of the nepovirus Arabis mosaic virus (ArMV) encodes a polyprotein from which protein 2A is released by proteolytic cleavage at the N-terminus. The 2A gene of 19 ArMV isolates from different geographical origin and 9 distinct natural hosts was amplified by RT/PCR and subsequently cloned and sequenced. These 19 isolates and those from databanks were classified into four groups based on the size of the protein 2A which ranged from 233 to 280 amino acids, and sequence identities. Sequence variability was mainly located in the N-terminus of the proteins, whereas the core region and the C-terminus were conserved