The transmission specificity and efficiency of tospoviruses

Recent studies analyzing nucleocapsid protein gene have revealed the existence of a broad genetic diversity of tospoviruses. In Brazil, six tospoviruses have been reported in agricultural, horticultural and floral crops. The viruses 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 (de Ávila et al., 1993, Bezzera et al., 1999, Nagata et al., 1998). In the Federal District, Brazil, four potential thrips vector species, Frankliniella occidentalis, F. schultzei, Thrips tabaci and T. palmi, were used in a study to compare the efficiency by which they transmit these viruses (Nagata et al., 1999a). F. occidentalis and T. palmi are considered as recently introduced species in this country (Monteiro et al., 1995a, b, 2000). T. palmi, which causes tremendous crop losses on green pepper, potato and cucurbits (Monteiro et al., 2000), seems to be an important vector of tospoviruses in east and south Asian countries. In Europe and USA, F. occidentalis is considered to be the major vector of TSWV and Impatiens necrotic spot virus (INSV). In such diversity of tospoviruses and potential vector species, the elucidation of vector competence of tospoviruses in Brazil may be of great interest to provide a foundation to design effective management strategies. The four above mentioned thrips species were tested for the efficiency by which the four tomato infecting tospoviruses are transmitted. After 16 h acquisition of virus by first instar larvae, the thrips were maintained on non-infected leaves till the adult stage, and the ability to transmit the virus was evaluated using leaf disk assay combined with ELISA (Wijkamp and Peters, 1993). F. occidentalis transmitted all four tospoviruses with varying efficiency according to the virus species, from 18 % with GRSV to 71 % Tatsuya Nagata1, Ana Carla Leite Almeida2, Renato de Oliveira Resende3 & Antonio Carlos de Àvila2. 1Biotecnologia Genomica, Universidade Catolica de Brasilia, Campo II, 916 Norte, 70790-160, Brasilia, DF, Brazil. 2Departamento de Virologia, EMBRAPA/Hortaliças, C.P. 218, 70359-970, Brasilia, DF, Brazil, 3Deptamento de Biologia Celular, Universidade de Brasilia, 70970-000, DF, Brazil. E-mail: [email protected]