以ＰＶＹ、ＣＭＶ及烟草为材料，研究ＲＮＡ介导抗病性的特点及遗传稳定性，研究不同有效ｃＤＮＡ片段组合连接后转化植物对抗病性的影响，探索以此来增强转基因植物对病毒的抗性及抗病性持久性、扩展抗病范围（同时抗几个流行病毒株系）以及多抗（同时抗两种以上病毒）基因工程策略的可行性及应用价值。

cDNAs covering the full genome of potato virus Y (PVY) were cloned by transcription-ploymerase chain reaction. Point mutation techniques were used to get rid of any possible start codons in the cDNA fragments. Plant expressing vectors containing segments from different region, different length and different slicing strategies were constructed. The plant expressing vectors were transformed into tobacco. Molecular hybridization analysis and resistance identification showed that the transformed cDNA fragments were expressed successfully at the transcription level, but no translated productions were examined. The transgenic plants showed high resistance to PVY infection. These results revealed that the resistance to PVY infection was mediated at RNA level. The resistance mediated by the cDNA from 3' region of the PVY CP gene was much stronger than that of 5' region, and the minimum length of cDNA was 200bp for resistance initiation. The results also showed that the best construction is the inverted repeat, from which the transcript could form hairpin construction. Based on these results, plant expressing vectors containing the cDNAs from the 3' regions of both PVY and potato virus X (PVX) CP genes were constructed in such way in which inverted repeats of their transcripts could be formed. The transgenic plants transformed with such constructs showed high resistance to both PVY and PVX infections.