Location: Floral and Nursery Plants ResearchTitle: Pectobacterium carotovorum. subsp. brasiliense is a causal agent of bacterial leaf rot of tobacco in China
|WANG, JING - Chinese Academy Of Agricultural Sciences|
|WANG, YIHONG - Chinese Academy Of Agricultural Sciences|
|DAI, PEIGANG - Chinese Academy Of Agricultural Sciences|
|CHEN, DEXIN - Chinese Academy Of Agricultural Sciences|
|ZHAO, TINGCHANG - Chinese Academy Of Agricultural Sciences|
|LI, XIAOLONG - China National Tobacco Corporation Nanjing Compamy|
Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/9/2016
Publication Date: 1/9/2017
Citation: Wang, J., Wang, Y., Dai, P., Chen, D., Zhao, T., Li, X., Huang, Q. 2017. Pectobacterium carotovorum. subsp. brasiliense is a causal agent of bacterial leaf rot of tobacco in China. Plant Disease. 101(5):830.
Interpretive Summary: A new leaf rot disease of tobacco was observed in Shaowu region, Fujian Province of China. A bacterial pathogen was determined to be the causal agent of the disease because the isolated bacterium from diseased tobacco leaves in the affected field caused similar disease symptoms when the bacterium was used to infect healthy tobacco plants. Our study is the first step towards effective control of the newly discovered tobacco disease in China.
Technical Abstract: A new leaf rot disease of tobacco was found in fields of the Shaowu region, Fujian Province of China in 2015. A typical symptom was necrosis along the main or lateral veins of tobacco leaves, eventually causing wilting and death of the leaves, while the necrosis spread no further than the epidermis of stem. In order to determine the causal agent of the disease, pathogenic bacteria were isolated from diseased leaf samples obtained from Shaowu and plated on nutrient agar (NA). One predominant type of bacterial colonies formed shiny, convex, grayish white, translucent and round colonies on nutrient agar. This bacterium was designated as FM6. FM6 caused macerated leaf veins and leaf death when stab-inoculated under greenhouse conditions. The bacterium re-isolated from the artificially infected plants showed similar colony morphology and characteristics, demonstrating that FM6 is a causal agent of the tobacco leaf disease in China. FM6 also caused dark lesions on potato tubers and soft rot on okra, cabbage, carrot, celery, eggplant, squash, cowpea, and green pepper within 48 h of inoculation, suggesting its potential threat to vegetable production in China. Morphological analysis showed that FM6 is a gram-negative facultative anaerobe, grows and forms pits on crystal violet pectate (CVP) medium, forms cream-colored non-fluorescent pigment on King's B medium, and is able to grow at 370C on nutrient agar, indicating that it belongs to the genus Pectobacterium. Physiological and biochemical analysis based on Biolog’s GEN III Microplate confirmed FM6 as the species P. carotovorum. The 16S rRNA gene sequence of FM6 was found to be most closely related to the known P. carotovorum subsp. brasiliense strain C18 with 99% sequence identity, suggesting that FM6 is also a member of the subspecies brasiliense. Furthermore, FM6 was phenotypically similar to the South African strains in Clade II of P. carotovorum subsp. brasiliense. This is the first report that P. carotovorum subsp. brasiliense causes bacterial leaf rot disease of tobacco in China.