Engineering Floricultural Crops for Resistance to Tomato spotted wilt virus

Tospoviruses are a major threat to the production of greenhouse ornamental and horticultural crops worldwide. Two closely-­?related species of tospoviruses found in the US -­? TSWV (Tomato spotted wilt virus) and INSV (Impatiens necrotic spot virus), can both infect a wide range of commercially-­?important plant species. Tospoviruses are vectored exclusively by several species of thrips, which rank among the major insect pests of greenhouse operations. In particular, it was the spread of western flower thrips (Frankliniella occidentalis) from western North America to many other parts of the world on infested plant material that has contributed to the continued occurrence of tospovirus epidemics, which often result in economic losses to growers. We propose to introduce TSWV resistance into the model plant Nicotiana benthamiana, a highly susceptible host for this virus, using a technology known as post-­?transcriptional gene silencing (PTGS), or RNA interference (RNAi). Employing established methods, we will generate plants that express gene-­?silencing constructs derived from the partial sequences of two TSWV genes. We will identify stable transformants and quantitatively test these plants, their progeny, and the appropriate controls for their relative susceptibility to TSWV infection. There is ample precedence in the scientific literature for the use of RNAi-­?based strategies to engineer resistance to plant viruses in several viral families. Our previous experience with another RNA virus, Tobacco etch virus (TEV), has shown that N. benthamiana plants expressing gene silencing constructs derived from three TEV genes exhibited a high level of resistance (functional immunity) to subsequent TEV infection. Successful demonstration of engineered TSWV resistance in N. benthamiana will then allow us to apply this technology to greenhouse-­?grown ornamental crop species such as African violet, begonia, gloxinia, petunia, etc., as well as horticultural crops, such as tomatoes and peppers, that are highly susceptible to systemic TSWV infection. Engineered resistance to TSWV will be of great value to the floriculture industry because it will eliminate viral damage to susceptible crops, and will interrupt the thrips-­?plant-­?thrips infection cycle in production greenhouses because the resistant plants are no longer sources of TSWV.