Abstract: This invention is directed to a monopartite RNA viral vector comprising modified tobravirus RNA-1 comprising an inserted foreign RNA sequence. This invention is also directed to a bipartite RNA viral vector derived from a tobravirus, wherein the vector comprises one or more foreign RNA sequences. The invention is directed to a method of silencing one or more endogenous plant host genes and a method of simultaneously silencing a plant host gene and expressing a foreign gene in a plant host. Such methods comprise infecting a plant host with a bipartite vector comprising modified tobravirus RNA-1 and RNA-2.