Background: Soybean vein necrosis disease is caused by Soybean vein necrosis virus (SVNV). SVNV is genetically and serologically a distinct species of the genus Tospovirus within the family Bunyaviridae which are vectored by at least 12 species of the genera Thrips and Frankliniella in nature.
Objective:SVNV is the first Tospovirus known to infect soybean . In Egypt Tospovirus; including Impatiens necrotic spot virus (INSV), Iris yellow spot virus (IYSV) and Tomato Spotted Wilt Virus (TSWV), have been reported by different investigators, but no information about SVNV. Therefore, the objective of this study is to identify and characterize a new Tospovirus associated with soybean. The transmission efficiency of SVNV by different thrips species is also determined as well as the incidence of viruliferous thrips and the role of weeds as reservoirs of both virus and vectors.
Methods: A virus isolate infecting soybean (Glycine max L.) plants showing symptoms suspected to be due to SVNV was collected from the Experimental farm of Faculty of Agriculture, Cairo University ,Giza Governorate during May 2014/2015. To identify the causal virus, the plants were tested by enzyme-linked immune-sorbent assay using antibodies against different Tospovirus i,e. Tomato spotted wilt virus (TSWV), Iris yellow spot virus (IYSV) and SVNV. Identification of this virus also was based on host range,transmissibility ,serological tests and electron microscopy
Results: The present study, confirms the presence of naturally occurring SVNV on soybean plants in Egypt based on disease symptoms observed on infected soybean plants in both field and greenhouse which confirmed by double antibody sandwich (DAS-ELISA) using SVNV specific antiserum and by tissue and dot blotting immuneo-binding assay. SVNV was able to infect only 11 plant species from 28 tested by mechanical inoculation. The virus was transmitted by mechanical means and by phytophagous thrips species; the most efficient vector was Neohydatothrips variabilis (Beach) (62.0%) while Frankliniella occidentalis (Pergande), Caliothrips phaseoli (Hood) and Megalurothrips sjostedti (Trybom) gave 3.4 %, 6.7 % and 3.3% transmission, respectively. Both N. variabilis and C. phaseoli were newly recorded on soybean crops in the present study. Electron micrograph revealed the presence of isometric shaped particles 80–100 nm diameter, typical of Tospovirus. The incidence of SVNV disease reached its maximum (66.7%) by the end of the soybean season Conclusion: The management of SVNV in soybean filed should focus on the thrips vector of the virus, and the plant hosts that sources of inoculums for spread of SVNV to and within soybean fields.
Soybean (Glycine max L.), Soybean vein necrosis virus (SVNV), Identification, Thrips ,Thysanoptera, Tospoviruses, Thrips transmission.