Maize dwarf mosaic virus and maize rough dwarf virus-resistant selectable marker-free siRNA composite expression vector and construction method thereof

The invention discloses a maize dwarf mosaic virus and maize rough dwarf virus-resistant selectable marker-free siRNA composite expression vector and a construction method thereof. The method comprises the following steps of: respectively amplifying specific fragments of coat protein genes of maize dwarf mosaic virus and maize rough dwarf virus by reverse transcription-polymerase chain reaction (RT-RCR) so as to construct an inverted repeat expression vector, and serially connecting two inverted repeat fragments of coat proteins of the maize dwarf mosaic virus and the maize rough dwarf virus by using an intermediate vector; and performing enzyme cutting on a double T-containing eukaryotic expression vector, connecting the enzyme-cut vector to a Ubiquitin promoter and a Nos terminator, and connecting the serially connected repeat fragments to the vector to construct the maize dwarf mosaic virus and maize rough dwarf virus-resistant selectable marker-free siRNA composite expression vector. Dual-resistant plants