A NOVEL METHOD FOR TOSPOVIRUS ACQUISITION BY THRIPS

An in vitro feeding method for the acquisition of impatiens necrotic s pot tospovirus (INSV) and tomato spotted wilt tospovirus (TSWV) by wes tern flower thrips (Frankliniella occidentalis (Pergande) was develope d. This is the first system developed in which tospovirus viability wa s maintained in an in vitro technique specifically designed for thrips feeding. Three-day-old larvae of western flower thrips were caged in a cylindrical plastic tube with Parafilm membrane covering both ends. Leaf extracts from INSV- and TSWV-infected Nicotiana benthamiana or Da tura stramonium were prepared. Following one cycle of differential cen trifugation, the extract was placed on the membrane on one end of the cage. A second membrane was placed over the first membrane thus coveri ng the extract. After a 24-h acquisition access feeding period, thrips were kept on green-bean pods in a container until they were 10-day-ol d adults. Enzyme-linked immunosorbent assays (ELISA) showed that acqui sition feeding of virus suspensions prepared from infected plant hosts resulted in thrips testing positive for viruses. Cohorts from these E LISA-positive thrips were shown to be viruliferous when placed onto vi rus-susceptible host plants. This in vitro method is an important tool in the study of tospovirus/thrips interactions.