Populations of onion thrips, Thrips tabaci Lindeman (Thysanoptera: Thripidae), were shown to differ significantly in their ability to transmit an isolate of tomato spotted wilt virus (Tospovirus: Bunyaviridae) (TSWV) collected from potato [Solanum tuberosum L. (Solanaceae)]. To gain an understanding of the basis for this variation, we generated reciprocal crosses between an efficient and an inefficient transmitting population. The resulting F 1 progeny and progeny from the parental populations were tested for their ability to transmit TSWV. Our results indicate that the ability to transmit TSWV efficiently by T. tabaci is inherited as a recessive trait. © 2007 The Authors.