High-throughput sequencing technologies were used to identify plant viruses in cereal samples surveyed from 2012 to 2017. Fifteen genome sequences of a tenuivirus infecting wheat, oats, and spelt in Estonia, Norway, and Sweden were identified and characterized by their distances to other tenuivirus sequences. Like most tenuiviruses, the genome of this tenuivirus contains four genomic segments. The isolates found from different countries shared at least 92% nucleotide sequence identity at the genome level. The planthopper Javesella pellucida was identified as a vector of the virus. Laboratory transmission tests using this vector indicated that wheat, oats, barley, rye, and triticale, but none of the tested pasture grass species (Alopecurus pratensis, Dactylis glomerata, Festuca rubra, Lolium multiflorum, Phleum pratense, and Poa pratensis), are susceptible. Taking into account the vector and host range data, the tenuivirus we have found most probably represents European wheat striate mosaic virus first identified about 60 years ago. Interestingly, whereas we were not able to infect any of the tested cereal species mechanically, Nicotiana benthamiana was infected via mechanical inoculation in laboratory conditions, displaying symptoms of yellow spots and vein clearing evolving into necrosis, eventually leading to plant death. Surprisingly, one of the virus genome segments (RNA2) encoding both a putative host systemic movement enhancer protein and a putative vector transmission factor was not detected in N. benthamiana after several passages even though systemic infection was observed, raising fundamental questions about the role of this segment in the systemic spread in several hosts.

Department of Chemistry and Biotechnology Tallinn University of Technology Akadeemia tee 15 Tallinn 10618 Estonia

Department of Plant Biology Swedish University of Agricultural Sciences Almas allé 5 Uppsala 75651 Sweden

Division of Biotechnology and Plant Health Norwegian Institute of Bioeconomy Research Høgskolevegen 7 Ås 1433 Norway

Division of Crop Protection and Plant Health Crop Research Institute Praha 16106 Czech Republic

Division of Plant Protection Estonian Crop Research Institute Aamisepa 1 Jõgeva 48309 Estonia

INRA UR407 Unité de Pathologie Végétale Montfavet 84140 France

Institute of Agricultural and Environmental Sciences Estonian University of Life Sciences Kreutzwaldi 1 Tartu 51006 Estonia

Integrated and Urban Plant Pathology Laboratory Gembloux Agro Bio Tech University of Liège Passage des Déportés 2 Gembloux 5030 Belgium

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