The inhibition of infectivity of Tobacco mosaic virus by tannins extracted from plants

The antiTMV activities of tannins extracted from 11 kinds of plants were determined. Infectivity of Tobacco mosaic virus (TMV) on Nicotiana glutinosa was strongly inhibited (more than 80%) by tannins (5.000 or 2.500 mg·mL-1) extracted from each kind of plants incubated with TMV for 10 mins. Strong inhibition (more 80%) was also showed when leaves were inoculated with TMV after incubated immediately with tannins at 5.000 mg·mL-1. The infectivity of TMV was recovered by dialysis for 3 days from incubations in vitro with tannins, but inhibition was reduced for tannins extracted from some kinds of plant after incubated with TMV for 3 days. Tannins of all plants did not affect multiplication of TMV in infected leaf discs. Tannins extracted form Euphorbia hirta, Polygonum perfoliatum, P.cuspidatum reduced infectivity when applied immediately on N.glutinosa before TMV inoculation. It also retarded symptom expression for 3-8 days in first leaves of N.tobacum cv.K326 when applied immediately before TMV inoculation.