ARTHROPODS IN RELATION TO PLANT DISEASE Diversity of Thrips Species and Vectors of Tomato Spotted Wilt Virus in Tomato Production Systems in Kenya ISAAC MACHARIA, 1,2,3 DAVID BACKHOUSE, 1 ROB SKILTON, 4 ELIJAH ATEKA, 5 SHU-BIAO WU, 1 MOSES NJAHIRA, 4 SOLOMON MAINA, 4 AND JAGGER HARVEY 4 J. Econ. Entomol. 108(1): 20–28 (2015); DOI: 10.1093/jee/tou010 ABSTRACT Thrips have been recognized as primary vectors of tomato spotted wilt virus (TSWV) with Frankliniella occidentalis (Pergande) reported as the most important and efficient vector, while other species such as Thrips tabaci Lindeman also include populations that can vector the virus. A study was undertaken to establish the diversity of thrips and presence of vectors for TSWV in four major tomato production areas in Kenya. The cytochrome oxidase 1 (CO1) gene was used to generate sequences from thrips samples collected from tomatoes and weeds, and phylogenetic analysis done to establish the variation within potential vector populations. Ceratothripoides brunneus Bagnall was the predominant species of thrips in all areas. F. occidentalis and T. tabaci were abundant in Nakuru, Kirinyaga, and Loitokitok but not detected at Bungoma. Other vectors of tospoviruses identified in low numbers were Frankliniella schultzei (Trybom) and Scirtothrips dorsalis Hood. Variation was observed in T. tabaci, F. occidentalis, and F. schultzei. Kenyan specimens of T. tabaci from tomato belonged to the arrhenoto- kous group, while those of F. occidentalis clustered with the Western flower thrips G group. The detec- tion of RNA of TSWV in both of these species of thrips supported the role they play as vectors. The study has demonstrated the high diversity of thrips species in tomato production and the occurrence of impor- tant vectors of TSWV and other tospoviruses. KEY WORDS Thysanoptera, tospovirus, phylogenetic analysis, molecular diagnosis, Solanum lycopersicum Introduction Thrips (Thysanoptera: Thripidae) are among the most economically important pests in crop production systems. They can cause physical damage on leaves and fruits and act as important vectors of viruses in vegeta- ble and ornamental production. Most thrips species are polyphagous, attacking both perennial and annual crops, hence supporting their survival and invasiveness. They have been reported as the sole vectors of tospovi- ruses with at least 14 thrips species consisting of eight Frankliniella species, three Thrips species, and one species of each Scirtothrips, Dictyothrips, and Cerato- thripoides shown as important vectors of tospoviruses (Riley et al. 2011). Among these, nine thrips species are vectors of tomato spotted wilt virus (TSWV): Frank- liniella occidentalis (Pergande) (Western flower thrips), Frankliniella schultzei (Trybom) (common blossom thrips), Frankliniella fusca (Hinds) (tobacco thrips), Frankliniella bispinosa (Morgan), Frankliniella intonsa (Trybom), Frankliniella cephalica (Crawford), Frank- liniella gemina Bagnall, Thrips tabaci Lindeman (onion thrips), and Thrips setosus Moulton (Pappu et al. 2009, Riley et al. 2011). F. occidentalis has been reported to be the most effi- cient vector and readily retains acquired virus through- out its life (Wijkamp et al. 1995). Its high fecundity, efficient and rapid dispersal ability, and polyphagous nature enable even a small number of Western flower thrips to transmit TSWV to a substantial number of plants (Riley et al. 2011). F. occidentalis has also been reported as a vector of other tospoviruses including im- patiens necrotic spot virus, chrysanthemum stem ne- crosis virus, groundnut ringspot virus and tomato chlorotic spot virus (TCSV; Pappu et al. 2009, Riley et al. 2011). Transmission studies have shown variation in the competence of T. tabaci as a vector of TSWV (Jacobson et al. 2013, Westmore et al. 2013). Both poor and effi- cient transmitting populations have been observed in Europe, Australia, and the United States (Chatzivassi- liou et al. 2000, Wilson 2001, Jenser et al. 2003, Jacob- son and Kennedy 2013, Westmore et al. 2013). Similar observations were reported with F. schultzei where the dark form was considered to be a more prolific vector of tospoviruses than the pale form (Sakimura 1969, 1 School of Environmental and Rural Science, University of New England, Armidale, NSW 2351, Australia. 2 Kenya Plant Health Inspectorate Service (KEPHIS), P.O. Box 49592, Nairobi 00100, Kenya. 3 Corresponding author, e-mail: macharia.isaac@gmail.com. 4 Biosciences Eastern and Central Africa -International Livestock Research Institute Hub (BecA-ILRI Hub), P.O. Box 30709, Nairobi 00100, Kenya. 5 Department of Horticulture, Jomo Kenyatta University of Agricul- ture and Technology (JKUAT), P.O. Box 62000, Nairobi 00200, Kenya. V C The Authors 2015. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com Downloaded from https://academic.oup.com/jee/article/108/1/20/795206 by guest on 27 June 2022