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Spotted wilt caused by tomato spotted wilt virus (TSWV; family Bunyaviridae; genus Tospovirus) is a serious disease of peanut (Arachis hypogaea L.) in the southeastern United States. Peanut genotypes with field resistance to TSWV are effective in suppressing spotted wilt. All commercially available genotypes with field resistance to TSWV were developed through conventional breeding. As a part of the breeding process, peanut genotypes are regularly screened under field situations. Despite numerous advantages associated with field screening, it is often limited by inconsistent vector (thrips) and TSWV pressure. A greenhouse transmission protocol would aid in thorough screening of selected genotypes and conserve time. In this study, various parameters associated with TSWV transmission, including tobacco thrips, Frankliniella fusca (Hinds) density, mode of inoculation, and plant age, were evaluated. Greater incidences of TSWV infection were obtained with thrips-mediated inoculation when compared with mechanical inoculation. TSWV inoculation with three, five, and 10 thrips resulted in greater incidences of TSWV infection in plants than inoculation with one thrips. However, incidences of TSWV infection did not vary between plants inoculated with three, five, and 10 viruliferous thrips. With both thrips-mediated and mechanical inoculation methods, incidences of TSWV infection in 1-wk-old plants were greater than in 4-wk-old plants. TSWV copy numbers, as determined by qPCR, also decreased with plant age. Results suggest that using at least three thrips per plant and 1- to 2-wk-old plants would maximize TSWV infection in inoculated plants. [ABSTRACT FROM PUBLISHER]

Iris yellow spot virus (IYSV) can severely affect onion production. IYSV is transmitted by the onion thrips, Thrips tabaci. However, information on IYSV-thrips-onion interactions is limited due to the difficulty associated with infecting onion plants experimentally. Lisianthus (Eustoma russellianum) was used as an indicator host to study mechanical transmission of IYSV, IYSV transmission by T. tabaci, IYSV distribution in the host plant, and the effect of temperature on IYSV symptom expression. Mechanical inoculation tests from IYSV-infected onion plants to noninfected lisianthus plants resulted in a mean transmission rate of 82.5 ± 6.9% (mean ± standard error), and from IYSV-infected lisianthus plants to noninfected lisianthus plants resulted in a mean transmission rate of 89.2 ± 7.1%. T. tabaci adults transmitted IYSV at a rate of 80.0 ± 8.3% from infected onion plants to noninfected lisianthus plants. To assess IYSV distribution in infected lisianthus plants, leaf sections, stems, and roots were tested by enzyme-linked immunosorbent assay (ELISA). All the plant parts tested positive for IYSV, but not on every plant assayed. Alternating night and day temperatures of 18 and 23°C, 25 and 30°C, and 30 and 37°C were evaluated for the effects on IYSV symptom expression. More severe symptoms developed on inoculated plants incubated at the 18 and 23°C or 25 and 30°C temperature regimes than at the 30 and 37°C regime, and symptoms were observed earliest on plants incubated at the 25 and 30°C temperature regime compared to the other temperature regimes. [ABSTRACT FROM AUTHOR]