Method for preparing inhibitor for reducing tobacco nicotine synthesis by double-stranded RNA interference technology and application thereof

The invention discloses a method for preparing an inhibitor for reducing tobacco nicotine synthesis by a double-stranded RNA interference technology and an application thereof. The method comprises extracting RNA from tobacco, carrying out reverse transcription to obtain cDNA of a tobacco putrescine-N-methyltransferase (PMT) gene, amplifying a fragment of the gene cDNA through a PCR technology, connecting the fragment to a plasmid vector PET-21a for expressing RNA, transferring the plasmid into an RNAE3 enzyme-free Escherichia coli cell, expressing a hairpin dsRNA, crushing the cell to obtain a dsRNA crude preparation, and orderly adding glycerol, a protectant and a dispersant into the dsRNA crude preparation to obtain the inhibitor for reducing tobacco nicotine synthesis. The inhibitor is applied to tobacco according to a ratio of 5 to 15mL/plant so that tobacco nicotine synthesis is reduced. The method has the advantages of simple production processes, low cost, and no damage to human, domestic animals and higher animals, is suitable for large-scale application for tobacco, and has a wide industrial prospect.