Pathogen Identification Of Populus × Euramericana Canker Disease

This study mainly identified pathogen of a new canker, which has been observed on stem and branch of Populus xeuramericana cv.'74/76' and P.×euramerican 'zhonglin 46' in Henan, Shandong Province and Tianjin City. Pathogens were isolated from the infected tissues, and pathogenicity test, fungicide bioassay and a preliminary survey of pathogenesis reqularity were conducted. The main research conclusions were as follows:1. The disease is characterized by canker with white exudates dripping the bark appeared mainly in the summer and abundant white smelly exudates were flowing from the cracks. The trunk phloem next to the crack was necrotic and occasional dieback of twigs and stem tops was observed. Diseased trees even died in serious cases.2. Used tissue isolation and leach solution to isolate pathogen, and inoculation the isolations in the glasshouse and in poplar stand to test the pathogenicity. Fungus strain Mz01 and bacterial strains named as N-5-1,4-4,1031 were pathogenic. Combined the result of cultural characteristics analysis, physiological, biochemical and molecular assay, both fungus Fusarium solani and bacterium Brenneria quercina were considered as the pathogens causing Populus×euramericana canker disease. This is the first report of poplar canker caused by Brenneria quercina in China.