Preliminary Study Of The Disease Survey And Pathogen Isolation And Infected Dynamicstate Of Tobacco Bacterial Wilt In Yunnan Province

In recent years, the bacterial wilt of tobacco has been more and more serious when leaf harvested in south of Yunnan Province especially Wenshan area, more than 80% infected disease some areas or all leaves would be dead. This paper was aimed to do the systemic survey and the researches on pathogen isolation of the disease about the bacterial wilt of tobacco at regular periods for finding the present conditions and providing reference for treatment.1. From 2004 to 2007, the survey and pathogen isolation of tobaccos with bacterial wilt disease were carried out in Wenshan province. The tobacco affected with lower stem black necrotic was due to bacterial wilt, black shank and mixed effect with bacterial wilt and black shank, their percentages were 86.3%, 27.7% and 14% respectively in the major tobacco planted counties such as Wenshan, Yanshan, Guangnan, Xichou and Malipo county in Wenshan prefecture.2. 91 strains of Ralstonia solanacearum were isolated from 170 samples gathered from 7 counties such as Wenshan, Baoshan and Simao of Yunnan province. The pathogen backward inoculation test and ELISA test were showed that it was mostly affected by tobacco bacterial wilt, partially with black shank for lower stem black necrosis prefecture in Wenshan and Baoshan.3. This research on infection and pathogenesis dynamics of Wenshan tobacco affected with Ralstonia solanaceanm was systemically processed by digging roots and ELISA detection at the fixed location and time. The results of investigation and detection after transplanting by digging weekly indicated that the roots were affected in the fifth week after transplanting and some roots showed the black necrosis; 50% of the roots were detected with Ralstonia solanaceanm and black necrosis appeared on several tobacco stems in the seventh week after transplanting; the pick out rate of Ralstonia solanaceanm in stems and roots raised up to more than 80% when the tobacco were transplanted in the twelfth week. There were intervals between the three periods of the positive detection in the roots sample, the symptoms appearing on the roots and the one appearing on the stems. And the interval of the three periods was about 21 days. The first two periods should be taken as the first and second application time to prevent the tobacco bacterial wilt disease respectively.