ABSTRACT
In Georgia, tomato spotted wilt tospovirus (TSWV) causes significant losses in peanut, tobacco, tomato, and pepper. Transmission of TSWV in Georgia primarily is by tobacco thrips (TT), Frankliniella fusca (Hinds), and western flower thrips, F. occidentalis (Pergande), with TT being the predominant vector species in peanut (2). TSWV must be acquired at the larval stage for the adult to transmit the virus. Detection of NSs (a non-structural TSWV protein present only following virus replication) in thrips by enzyme-linked immunosorbent assay (ELISA) is a reliable indicator that the virus had multiplied in the vector and thus the vector is competent to transmit TSWV. While this has been accomplished with F. occidentalis (1), information is lacking for F. fusca, the predominant vector in Georgia and other states in the Southeast. Thus, the nature of the TSWV-TT association was investigated and the proportion of transmitters in a field population determined in 1,436 individual adult TT collected from sticky cards positioned in selected peanut fields in south Georgia. Additionally, 650 larvae collected from volunteer peanut plants were reared to adults in the laboratory and the resulting 295 adult TT were individually evaluated by ELISA. Of those collected from the sticky cards, NSs was detected in 8% of the adult insects, indicating that the virus had multiplied in TT. NSs was not detected in control TT that had no access to the virus. Of the adult TT that emerged from larvae collected from volunteer peanuts, 6.1% were positive for NSs. Our study provides the first immunological evidence that TSWV multiplies in TT. References: (1) M. D. Bandla et al. Phytopathology 84:1427, 1994. (2) J. R. Chamberlin et al. J. Econ. Entomol. 86:40, 1993.
ABSTRACT
ABSTRACT Interactions between viral and cellular membrane fusion proteins mediate virus penetration of cells for many arthropod-borne viruses. Electron microscope observations and circumstantial evidence indicate insect acquisition of tomato spotted wilt virus (TSWV) (genus Tospovirus, family Bunyaviridae) is receptor mediated, and TSWV membrane glycoproteins (GP1 and GP2) serve as virus attachment proteins. The tospoviruses are plant-infecting members of the family Bunyaviridae and are transmitted by several thrips species, including Frankliniella occidentalis. Gel overlay assays and immunolabeling were used to investigate the putative role of TSWV GPs as viral attachment proteins and deter mine whether a corresponding cellular receptor may be present in F. occidentalis. A single band in the 50-kDa region was detected with murine monoclonal antibodies (MAbs) to the TSWV-GPs when isolated TSWV or TSWV-GPs were used to overlay separated thrips proteins. This band was not detected when blots were probed with antibody to the non-structural protein encoded by the small RNA of TSWV or the TSWV nucleocapsid protein, nor were proteins from nonvector insects labeled. Anti-idiotype antibodies prepared to murine MAbs against GP1 or GP2 specifically labeled a single band at 50 kDa in Western blots and the plasmalemma of larval thrips midguts. These results support the putative role of the TSWV GPs as viral attachment proteins and identified potential cellular receptor(s) in thrips.
