Acquisition, Replication and Transmission of Soybean Vein Necrosis Virus (SVNV) by Neohydatothrips variabilis, Frankliniella tritici, and F. fusca (Thysanoptera: Thripidae) in Soybean
Abstract
Soybean vein necrosis virus (SVNV) is a newly identified soybean virus, involved in genus Tospovirus, which is exclusively transmitted by thrips in a persistent-propagative manner. Until recently, Neohydatothrips variabilis (soybean thrips) was the only known vector of SVNV, however, Frankliniella tritici (eastern flower thrips) and F. fusca (tobacco thrips) have also been confirmed as vectors of SVNV. Hence, the goal of this study was to investigate vector competence (acquisition, replication and transmission efficiencies) of SVNV by N. variabilis and the two other thrips vector species. Using quantitative real-time PCR (qPCR), I showed a significant relationship between virus acquisition time and proportion of transmitting adult N. variabilis. Less than 10% and 17% of transmission rates were observed by N. variabilis at 6 and 48h AAP, although there were similar viral copies were detected at 6h AAP compared to those after 12 and 24h AAP, except for 48h AAP, which had significant lower viral copies. Overall, N. variabilis containing 103 and 104 of log copies of viral RNA had significantly higher success of transmission rate than those containing ≤ 102 and ≤ 105 of viral copies. Consistent with other studies, our immunolabeling results on N. variabilis revealed that the anterior of midgut cells are the initial sites of entry for SVNV and then the virus subsequently infects the surrounding muscle cells and eventually the salivary glands. SVNV was able to infect the alimentary canal after 6h AAP but, interestingly, a significant lower infection rate of salivary glands was observed at 6h AAP compared to 12, 24 and 48h AAP. Infection of salivary glands is pre-requisite for successful transmission of the virus. Analysis of SVNV progression in F. tritici and F. fusca revealed that virus infection occurs in the forgut (FG), midgut (MG), tubular salivary gland (TSG) that connect MG to primary salivary gland (PSG), as well as in the efferent duct and PSG. However, the infection percentage was lower in tobacco thrips and eastern flower thrips compared to the primary vector. Hence, successful transmission not only depends on virus acquisition but also replication and dissemination within the thrips vector. This study will increase fundamental and applied knowledge of virus-vector interactions for development of effective management strategies.
Degree
M.S.
Advisors
Nachappa, Purdue University.
Subject Area
Entomology|Virology
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