The yellow dwarf viruses (YDVs) of the Luteoviridae family represent the most widespread group of cereal viruses worldwide. They include the Barley yellow dwarf viruses (BYDVs) of genus Luteovirus, the Cereal yellow dwarf viruses (CYDVs) and Wheat yellow dwarf virus (WYDV) of genus Polerovirus. All of these viruses are obligately aphid transmitted and phloem-limited. The first described YDVs (initially all called BYDV) were classified by their most efficient vector. One of these viruses, BYDV-RMV, is transmitted most efficiently by the corn leaf aphid, Rhopalosiphum maidis. Here we report the complete 5612 nucleotide sequence of the genomic RNA of a Montana isolate of BYDV-RMV (isolate RMV MTFE87, Genbank accession no. KC921392). The sequence revealed that BYDV-RMV is a polerovirus, but it is quite distantly related to the CYDVs or WYDV, which are very closely related to each other. Nor is BYDV-RMV closely related to any other particular polerovirus. Depending on the gene that is compared, different poleroviruses (none of them a YDV) share the most sequence similarity to BYDV-RMV. Because of its distant relationship to other YDVs, and because it commonly infects maize via its vector, R. maidis, we propose that BYDV-RMV be renamed Maize yellow dwarf virus-RMV (MYDV-RMV).

The phytobiome includes not just cellular microorganisms, but also all viruses associated with plants: the virome. Plants and aphids exchange viruses regularly and efficiently; thus, the plant virome is tightly linked with the aphid virome. Yet, little is known about aphid viromes, particularly that of the soybean aphid (Aphis glycines), one of the most economically important pest insects of soybean. To sample the soybean aphid virome, and to seek new viruses as potential biological control agents, we employed next-generation sequencing. Genomes isolated from viruses in soybean aphids collected at four sites revealed many viruses, and six complete or nearly complete genomes were assembled. Most abundant were the picornavirus-like dicistroviruses Aphid lethal paralysis virus and Rhopalosiphum padi virus. We also sequenced the genome of a new dicistrovirus, Big Sioux River virus, fragments of which had been found previously in honey bee. Genome sequences that represent two entirely new virus families were obtained. These include an abundant tetravirus-like virus and a virus distantly related to cileviruses of plants and negeviruses of insects. Surprisingly, Cotton leafroll dwarf virus, a member of the genus Polerovirus, was found in soybean aphids from China, suggesting that the soybean aphid may be a vector of this virus. This virus had not been reported previously in China or in soybean. This study provides a peek into the rapidly expanding, largely unexplored world of insect viromes that will provide valuable knowledge for future understanding of plant−virus−vector interactions. [Formula: see text] Copyright © 2017 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

The cell line IPLB-LD-652Y, derived from the gypsy moth (Lymantria dispar L.), is routinely used to study interactions between viruses and insect hosts. Here we report the full genome sequence and biological characteristics of a small RNA virus, designated Lymantria dispar iflavirus 1 (LdIV1), that was discovered to persistently infect IPLB-LD-652Y. LdIV1 belongs to the genus Iflavirus. LdIV1 formed icosahedral particles of approx. 30 nm in diameter and contained a 10 044 nt polyadenylated, positive-sense RNA genome encoding a predicted polyprotein of 2980 aa. LdIV1 was induced by a viral suppressor of RNA silencing, suggesting that acute infection is restricted by RNA interference (RNAi). We detected LdIV1 in all tested tissues of gypsy-moth larvae and adults, but the virus was absent from other L. dispar-derived cell lines. We confirmed LdIV1 infectivity in two of these cell lines (IPLB-LD-652 and IPLB-LdFB). Our results provide a novel system to explore persistent infections in lepidopterans and a new model for the study of iflaviruses, a rapidly expanding group of viruses, many of which covertly infect their hosts.