First Report of Tobacco Bushy Top Disease in China

In 1993, a severe epidemic of a new disease of flue-cured tobacco (Nicotiana tabacum) occurred in western Yunnan Province, People's Republic of China. Since then, over 40,000 ha of tobacco have been affected, with an average incidence of ≈15%. Infected plants were stunted, and leaves showed symptoms of vein distortion, vein clearing, mottling, and rounding. Axillary buds sprouted from the main stem of infected plants early and formed lateral shoots, on which other shoots were produced. As a result, the infected plants presented the characteristic “bushy” appearance. Aphid- (Myzus persicae (Sulzer)) and sap-transmission experiments were conducted. In aphid-transmission tests, after an acquisition feeding period of 24 h on diseased tobacco, the shortest test feeding that resulted in infection was 5 min. The causal agent(s) was readily sap-transmissible, but it could not be transmitted from sap-inoculated plants to healthy plants by aphids. Thirty-two species of plants in eleven families were tested by sap-i...