Etiology And Diagnosis Of Tobacco Root And Stem Diseases In Fujian, China

In China, Fujian is one of the major tobacco production areas. The serious loss was caused by tobacco root and stem diseases every year. According to the survey of the tobacco root and stem diseases in Fujian province from2009to2012, four major root and stem diseases were diagnosised and etiological researched, such as tobacco fusarium root rot, tobacco damping-off, tobacco root and stem rot and tobacco black shank. The results were as follows:1. Tobacco damping-off was found for the first time in the floating seeding in Jianyang of Fujian province in March,2011. By the pathogen morphology observation and ITS sequence analysis, pathogen was identified as Pythium irregulare.2. In the tobacco field of tobacco-rice rotation, tobacco root and stem rot was found, the pathogen was identified as Rhizoctonia solani. Comparative studies and artificial cross-inoculation test of this pathogens and rice sheath blight pathogens reveal, the two kinds of Rhizoctonia have the common feature of the Rhizoctonia. The result that rice Rhizoctonia has strong pathogenicity on tobacco and tobacco Rhizoctonia also has strong pathogenicity on rice. The results show that the wintering sclerotium may become primary infection source of tobacco root and stem rot in the tobacco field of tobacoo-rice rotation.3. In recent years, tobacco fusarium root rot occurred commonly in Fujian province. Two kinds of Fusarium were isolated from the samples of tobacco fusarium root rot and were identified as Fusarium solani var. coeruleum and Fusarium oxysporum Schlecht. by morphology. Results of pathogenicity test showed that both two Fusarium were able to infection tobacco. Fusarium solanivar. coeruleum was the superior race and had the higher separation rate.4. In Ninghua, Sanming city of Fujian province in July2011, tobacco black shank was found for the first time since tobacco pest and disease survey was carried out from2009. By pathogens isolation, pathogenicity test, pathogens morphological observation and ITS sequence analysis, the pathogen is identified as Phytophthora parasitica var. nicotianae. The pathogen metalaxyl sensitivity test, the results indicated that it was hypersensitive and had not resistance to metalaxyl.