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Tomato chlorotic spot virus, an emerging tospovirus threatening vegetable production in the United States

Shouan Zhang: University of Florida

<div><em>Tomato chlorotic spot virus</em> (TCSV) is a tospovirus first detected in tomato and bell pepper in south Florida in 2012. Subsequently, TCSV was confirmed in tomato in Ohio and New York. Since 2014, TCSV has caused significant losses to tomato and bell pepper growers in south Florida. TCSV is efficiently transmitted by flower thrips, which are abundant in many regions of the USA. Initial symptoms of TCSV in tomato begin to appear on top leaves as tiny necrotic lesions three weeks after transplanting. Within one week, the symptoms quickly expand to cause bronzing, necrosis, deformation of leaves, and terminal stem and leaf death. In bell pepper, TCSV causes chlorosis on top leaves and necrosis over time. TCSV results in severe stunting and eventually death of the plant if plants are infected at an early stage. Infected plants produce few, if any, fruit with necrotic rings rendering them unmarketable. Field survey from 2016 to 2017 indicated that TCSV has become the dominant tospovirus in south Florida. In 2017, TCSV was also detected in snapbean and purslane in Homestead, FL. Reverse transcription loop-mediated isothermal amplification (RT-LAMP) was developed for specific detection of TCSV from tomato plants. Results of field trials in Homestead, FL indicate that tomato cultivars carrying <em>sw-5</em> gene are resistant to TCSV. Applying insecticides is not highly effective in reducing TCSV incidence, but can minimize secondary spread of TCSV by its thrips vectors.</div>