The competence of four thrips species to transmit and replicate four tospoviruses

The tospoviruses Tomato spotted wilt virus (TSWV), Tomato chlorotic spot virus (TCSV), Groundnut ringspot virus (GRSV) and Chrysanthemum stem necrosis virus (CSNV) are well-known pathogens on tomato in Brazil. The thrips species Frankliniella occidentalis, F. schultzei, Thrips tabaci and T. palmi were studied for their competence to transmit these tospoviruses. Frankliniella occidentalis transmitted all four tospoviruses with different efficiencies. Frankliniella schultzei transmitted TCSV, GRSV and CSNV. Although F. schultzei has been reported as a vector of TSWV, the F. schultzei population in the present study did not transmit the TSWV isolate used. A population of T. tabaci known to transmit Iris yellow spot virus (onion isolate) did not transmit any of the studied tospoviruses, and nor did T. palmi. Replication of these tospoviruses could be demonstrated by ELISA, not only in the thrips species that could transmit them, but also in those that could not. The results strongly suggest that competence to transmit is regulated not only by the initial amount of virus acquired and replication, but also by possible barriers to virus circulation inside the thrip's body.