Morphological and Molecular Identification of Fusarium ipomoeae as the Causative Agent of Leaf Spot Disease in Tobacco from China

Tobacco (Nicotiana tabacum L.), which creates jobs for 33 million people and contributes two trillion dollars' tax annually, is one of the most important economic plants globally. However, tobacco is seriously threatened by numerous diseases during production. Previously, the field survey of tobacco diseases was conducted in the Guizhou and Guangxi provinces, the two main tobacco-producing areas in China. A serious leaf spot disease, with a 22% to 35% incidence, was observed in farming plants. In order to determine the causal agents, we collected the disease samples and isolated the pathogenic fungi. The pathogen was identified as Fusarium ipomoeae, based on the morphological characteristics and phylogenetic analysis. Pathogenicity tests showed that F. ipomoeae could induce tobacco leaf spot and blight. To our knowledge, this is the first report worldwide of F. ipomoeae causing leaf spots and stems on tobacco. Our study reveals the serious consequences of F. ipomoeae on tobacco filed production and provides information for future diagnosis and management of the Fusarium disease.