Onion (Allium cepa L.) as a new host for 'Candidatus Arsenophonus phytopathogenicus' in Germany.

Onion (Allium cepa L.) is the most produced vegetable after tomato worldwide and is grown on about 15,000 ha in Germany. In Lampertheim, Hesse in southwest Germany (49°40'02.3"N, 8°26'00.0"E) bulbs of the cultivar 'Red Baron F1' were harvested in September 2023 in an apparently healthy state. Four months later some of the onions showed rotting symptoms, which could not be assigned to a known storage disease. At first, the bulbs became glassy, later they showed soft rot. They originated from a field located in a growing region severely affected by "Syndrome Basses Richesses" (SBR). 'Candidatus Arsenophonus phytopathogenicus' as well as 'Candidatus Phytoplasma solani' are associated with this disease in sugar beet (Gatineau et al. 2002). Moreover, 'Ca. A. phytopathogenicus' was recently reported in association of bacterial wilt and yellowing in potato (Behrmann et al. 2023). Both phloem-restricted bacteria are vectored by the polyphagous planthopper Pentastiridius leporinus (Therhaag et al. 2024), which is highly abundant in this region. To examine, if the unknown symptoms in onion might be related to the presence of these pathogens, DNA of 69 bulbs showing a different degree of softening were analyzed. The samples were tested for the presence of 'Ca. Phytoplasma solani' in a TaqMan assay (Behrmann et al. 2022). All showed negative results. To demonstrate the presence of 'Ca. A. phytopathogenicus', universal and genus-specific primers for the amplification of 16S rDNA and a real-time qPCR assay amplifying an hsp20 fragment were employed (Christensen et al. 2004, Zübert and Kube 2021). Two bulbs of the five positive samples were in an apparently healthy state, the other three showed light to moderate softening symptoms. The 16S rDNA fragments from two samples were sequenced on both strands and aligned. Both fragments were homologous. One fragment of 1474 bp fragment showing 100% homology to the 16S rDNA from SBR (accession no. AY057392) was submitted to GenBank (accession no. PP400342). Other taxa of 'Ca. Arsenophonus' showed 16S rDNA homologies of less than 99.3 %. To corroborate the finding onion samples were subjected to PCR reactions employing genus-specific primers for the conserved tufB, secY and manA gene, which had been derived from multiple alignments of 'Ca. A. spp' sequence submissions (Sela et al. 1989, Lee et al. 2010). The tufB, secY and manA primers amplified fragments of about 980 bp, 640 bp and 930 bp, respectively, from all previously positive samples. Samples which had been tested negative for 'Ca. P. phytopathogenicus' remained negative. Fragments from two accessions were sequenced and the sequences from both isolates were 100 % identical. A BLAST search of the partial tufB gene (acc. no. PP950434) showed 98.57 % sequence identity to a yet unnamed Arsenophonus endosymbiont (acc. no. OZ026540) and 91.85 to 91.83 % to 'Ca. A. nasoniae' and 'Ca. A. apicola', respectively. A similar result was obtained for the partial secY sequence (acc. no. PP950433). The manA sequence (acc. no. PP942231) was identical to a partial sequence of 'Ca. A. phytopathogenicus' strain HN (acc. no. OK335757) and 97.42 % to 'Ca. A. nasoniae and about 87 % to related Arsenophonus species. The finding of 'Ca. A. phytopathogenicus' in onion is novel and might indicate an expanding host range of vector and pathogen in the regional crop rotation. As a correlation between the pathogen and the soft rot symptom is unclear at present, further investigations are needed.

Biological and Genetic Characterization of Physostegia Chlorotic Mottle Virus in Europe Based on Host Range, Location, and Time.

Application of high throughput sequencing (HTS) technologies enabled the first identification of Physostegia chlorotic mottle virus (PhCMoV) in 2018 in Austria. Subsequently, PhCMoV was detected in Germany and Serbia on tomatoes showing severe fruit mottling and ripening anomalies. We report here how prepublication data-sharing resulted in an international collaboration across eight laboratories in five countries, enabling an in-depth characterization of PhCMoV. The independent studies converged toward its recent identification in eight additional European countries and confirmed its presence in samples collected 20 years ago (2002). The natural plant host range was expanded from two to nine species across seven families, and we confirmed the association of PhCMoV presence with severe fruit symptoms on economically important crops such as tomato, eggplant, and cucumber. Mechanical inoculations of selected isolates in the greenhouse established the causality of the symptoms on a new indexing host range. In addition, phylogenetic analysis showed a low genomic variation across the 29 near-complete genome sequences available. Furthermore, a strong selection pressure within a specific ecosystem was suggested by nearly identical sequences recovered from different host plants through time. Overall, this study describes the European distribution of PhCMoV on multiple plant hosts, including economically important crops on which the virus can cause severe fruit symptoms. This work demonstrates how to efficiently improve knowledge on an emergent pathogen by sharing HTS data and provides a solid knowledge foundation for further studies on plant rhabdoviruses.[Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Caraway yellows virus, a novel nepovirus from Carum carvi.

A novel nepovirus was identified and characterised from caraway, and tentatively named caraway yellows virus (CawYV). Tubular structures with isomeric virus particles typical for nepoviruses were observed in infected tissues by electron microscopy. The whole genome of CawYV was identified by high throughput sequencing (HTS). It consists of two segments with 8026 nt for RNA1 and 6405 nt for RNA2, excluding the poly(A) tails. CawYV-RNA1 shared closest nt identity to peach rosette mosaic virus (PRMV) with 63%, while RNA2 shared 41.5% with blueberry latent spherical virus (BLSV). The amino acid sequences of the CawYV protease-polymerase (Pro-Pol) and capsid protein (CP) regions share the highest identities with those of the subgroup C nepoviruses. The Pro-Pol region shared highest aa identity with PRMV (80.1%), while the CP region shared 39.6% to soybean latent spherical virus. Phylogenetic analysis of the CawYV-Pro-Pol and -CP aa sequences provided additional evidence of their association with nepoviruses subgroup C. Based on particle morphology, genomic organization and phylogenetic analyses, we propose CawYV as a novel species within the genus Nepovirus subgroup C.

Reassortants of the pandemic (H1N1) 2009 virus and establishment of a novel porcine H1N2 influenza virus, lineage in Germany.

The incursion of pandemic (H1N1) 2009 virus (pdmH1N1) into the German pig population was investigated in a serosurvey and by virological means between June 2009 and December 2012. Analysis of 23,116 pig sera from a total of 2,666 herds revealed 224 herds that reacted with pdmH1N1 but not with the prevalent avian-like H1N1 swine influenza virus. Sixty-six pdmH1N1 strains and their reassortant derivatives (pdmH1huN2, huH3pdmN1) have been collected since November 2009. Sequencing of three pdmH1N1, 20 pdmH1huN2 and one huH3pdmN1 strains with conventional and next generation sequencing techniques and subsequent phylogenetic analyses with available sequence data revealed the emergence of five distinct reassortant genotypes in Europe. The most frequent genotype emerged at least three times independently, one of which (Papenburg lineage) established a stable infection chain and became more prevalent in pigs than pdmH1N1 in Germany.