Effects of temperature and host on the generation of tomato spotted wilt virus defective interfering RNAs

The generation of defective interfering (DI) RNA molecules of tomato spotted wilt tospovirus (TSWV) was studied by serially passaging inocula from plant to plant under different controlled conditions. DI RNAs were generated at higher rates in plants at 16 degrees C than in plants incubated at higher temperatures. Another factor promoting the TSWV DI RNA generation was the use of high virus concentrations in the inocula. The solanaceous species Capsicum annuum, Datura stramonium, Lycoparsicon esculentum, Nicotiana benthamiana, and N. rustica supported the generation of DI RNAs, whereas the virus recovered from the inoculated composite species, Emilia sonchifolia, remained free of any DI RNA under all conditions tested; This study resulted in a strategy to maintain DI RNA-free TSWV isolates, as well as in an efficient way to produce a large population of different DT RNA species. A single DI RNA species usually became dominant in an isolate after a few rounds of serial inoculations. The possible mechanisms involved in TSWV DI RNA generation under different inoculation circumstances are discussed.