Nicotiana tabacum cv. NC89 plants were grown in plastic pots till the three leaf stage and were treated as follows.
1) the soil in each pot was drenched three times at 6 day intervals with 10 ml of 100-fold CZ dilution, nutrient broth medium or water. Fresh weight, plant height and area of the biggest leaf were measured 15 days after first drenching. Each treatment to six plants was repeated three times.
2) plants were sprayed three times at 6-day intervals with 10 ml of 100-fold CZ dilution, nutrient broth medium or water. The plants were inoculated with 160-fold TMV suspension 6 h after the last spray. All plants were examined for disease severity 15 days after inoculation. Each treatment consisted of twenty-five plants, and all experiments were repeated three times