First report of bacterial Wilt caused by Ralstonia solanacearum on Ageratum conyzoides in China.
Ageratum conyzoides is believed to act as reservoir host for many plant diseases. In June 2011, a 30% incidence of bacterial wilt on A. conyzoides was observed in a field of Rhizoma kaempferiae [Kaempferia galanga] in Yangchun city of Guangdong province, China. The initial symptoms were wilting of the apical leaves during the day, which recovered at night. After 4 to 6 days, the leaves became totally necrotic. The basal stems of the diseased plants were blackened and the vascular tissue turned brown. To investigate the disease aetiology before understanding the disease link between A. conyzoides and R. kaempferiae, 10 plants with typical wilting symptoms were collected from the field. A total of 10 bacterial isolates were isolated from the vascular tissue of each diseased plant. Based on the pathogenicity tests, carbohydrate utilization, and near full-length 16S rDNA sequences, the bacterial isolates from the diseased A. conyzoides belonged to race 4 and biovar 3 of R. solanacearum. This is thought to be the first report of a disease caused by R. solanacearum on A. conyzoides in China.