Transmissibility of four tospoviruses by a thelytokous population of Thrips tabaci from Liguria, northwestern Italy

Studies were carried out on a population of Thrips tabaci Lindeman (Thysano ptera: Thripidae) from Liguria to assess its sex-ratio and its ability to t ransmit four tospoviruses: tomato spotted wilt (TSWV), impatiens necrotic s pot, tomato chlorotic spot and groundnut ringspot. The population was compo sed of females only (therefore thelytokous). The first instar larvae were a llowed to acquire the virus for 48 h on infected leaves of datura, basil or pepper, and then reared on cucumber until emergence, which medially occurr ed 9.5 days after latching. Transmission capacity was checked using two ino culation access periods (IAPs) of 48 h each on pepper leaf disks. T. tabaci was able to transmit TSWV isolate P105 with an efficiency of 16.7% and 4.4 % in the first and second IAP, respectively, and TSWV isolate BR-01 with an efficiency of 2.0%. The onion thrips did not transmit the three other tosp oviruses. During the IAPs, almost all adults fed on the leaf disks, produci ng evident silvery scars. The presence of tospovirus nucleocapsids in thrip s was assayed by Triple Antibody Sandwich (TAS) and cocktail ELISA. Not all adults that had transmitted TSWV were positive in the tests, whereas some non-transmitter individuals proved positive. For each of the other tospovir uses, some thrips were positive in at least one test, although none was abl e to transmit the virus.