title: Seed Transmission of Soybean vein necrosis virus: The First Tospovirus Implicated in Seed Transmission.
abstract: Soybean vein necrosis virus (SVNV; genus Tospovirus; Family Bunyaviridae) is a negative-sense single-stranded RNA virus that has been detected across the United States and in Ontario, Canada. In 2013, a seed lot of a commercial soybean variety (Glycine max) with a high percentage of discolored, deformed and undersized seed was obtained. A random sample of this seed was planted in a growth room under standard conditions. Germination was greater than 90% and the resulting seedlings looked normal. Four composite samples of six plants each were tested by reverse transcription polymerase chain reaction (RT-PCR) using published primers complimentary to the S genomic segment of SVNV. Two composite leaflet samples retrieved from seedlings yielded amplicons with a size and sequence predictive of SVNV. Additional testing of twelve arbitrarily selected individual plants resulted in the identification of two SVNV positive plants. Experiments were repeated by growing seedlings from the same seed lot in an isolated room inside a thrips-proof cage to further eliminate any external source of infection. Also, increased care was taken to reduce any possible PCR contamination. Three positive plants out of forty-eight were found using these measures. Published and newly designed primers for the L and M RNAs of SVNV were also used to test the extracted RNA and strengthen the diagnosis of viral infection. In experiments, by three scientists, in two different labs all three genomic RNAs of SVNV were amplified in these plant materials. RNA-seq analysis was also conducted using RNA extracted from a composite seedling sample found to be SVNV-positive and a symptomatic sample collected from the field. This analysis revealed both sense and anti-sense reads from all three gene segments in both samples. We have shown that SVNV can be transmitted in seed to seedlings from an infected seed lot at a rate of 6%. To our knowledge this is the first report of seed-transmission of a Tospovirus.
authors.affiliation: Department of Plant Pathology, University of Wisconsin, 1630 Linden Drive, Madison, WI, 53706, United States of America.
authors.forename: Carol
authors.initials: C
authors.lastname: Groves
authors.affiliation: Department of Entomology, University of Wisconsin, 1630 Linden Drive, Madison, WI, 53706, United States of America.
authors.forename: Thomas
authors.initials: T
authors.lastname: German
authors.affiliation: Department of Entomology, University of Wisconsin, 1630 Linden Drive, Madison, WI, 53706, United States of America.
authors.forename: Ranjit
authors.initials: R
authors.lastname: Dasgupta
authors.affiliation: Department of Plant Pathology and Microbiology, Iowa State University, 351 Bessey Hall, Ames, IA, 50011, United States of America.
authors.forename: Daren
authors.initials: D
authors.lastname: Mueller
authors.affiliation: Department of Plant Pathology, University of Wisconsin, 1630 Linden Drive, Madison, WI, 53706, United States of America.
authors.forename: Damon L
authors.initials: DL
authors.lastname: Smith
mesh_terms: D015415:Biomarkers / Q000032:analysis; D018562:Disease Transmission, Infectious; D059014:High-Throughput Nucleotide Sequencing; D010935:Plant Diseases / Q000235:genetics / Q000276:immunology / Q000821:virology*; D010940:Plant Proteins / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D018749:RNA, Plant / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012639:Seeds / Q000235:genetics / Q000821:virology*; D013025:Glycine max / Q000235:genetics / Q000821:virology*; D017865:Tospovirus / Q000472:pathogenicity*
chemical_list: D015415:Biomarkers; D010940:Plant Proteins; D012333:RNA, Messenger; D018749:RNA, Plant