The virus types infecting tobacco plants in the fields of Hunan were investigated and tested by ELISA in laboratory in 2005 and 2006. The results showed that there were 6types such as CMV, TMV, PVY, PVX, TEV and TRSV on tobacco of Hunan. These virus types alone or combined infected the tobacco plants. ELISA test of 856 samples exhibiting mosaic symptom indic...