Symptoms and pathogen identification of tobacco bacterial leaf spot disease in Zhenghe,Fujian

【Objective】 To identify the pathogenic agent of tobacco(Yunyan 87) bacterial leaf spot disease newly found in Zhenghe County of Fujian in 2020, so as to provide a theoretical basis for further exploring the disease regularity and the precise control measures.【Method】 The bacterial strains were isolated and purified from disease leaves of tobacco Yunyan 87 in Zhenghe County of Fujianby the plate-marking method, the pathogenicity of the isolated strains were tested by Koch's Postulation, and its taxonomic status were confirmed by bacteria biological characteristics, physiological and biochemical characteristics, and specific primer detection and 16S rDNA gene sequence analysis.【Result】 The results showed that fifteen strains were isolated from diseased leaves of tobacco. According to Koch's Postulation, all the fifteen strains were the pathogens of tobacco bacterial leaf spot disease and their pathogenicity was no obvious difference. The colonies of the pathogen were bulge and white on NA plate in 1-2 d cultivation, the edges were irregular and thick.The bacterial cellswere rod-shaped and had 4 flagella on polar. Gram stain was negative. Based on 8 key physiological and biochemical characteristics, 94 phenotypes in Biolog instrument, specific primer detection and 16S rDNA sequence analy-sis of the pathogens, all 15 tested isolates were identified as Pseudomonas amygdali pv. tabaci.【Conclusion】 The tobacco bacterial leaf diseases in Zhenghe County of Fujian is caused by P. amygdali pv. tabaci.