First report of bacterial wilt caused by Ralstonia solanacearum on Mesona chinensis in China.

摘要

In June, 2009, a wilting disease of Xiancao (M. chinensis [Plastoma chinensis]) was observed in Guangdong and the neighbouring Guangxi and Fujian provinces (China) with incidence of up to 50%. Affected plants initially showed withering symptoms on apical leaves during the daytime, with recovery at night. As the disease progressed, withering leaves spread downward, eventually encompassing the whole plant. Leaves lost vigour but remained green. After 3-4 days, wilting became irreversible. Roots and basal stem tissues blackened and rotted, resulting in plant death. Longitudinal sectioning of the basal stem showed browning of vascular tissues with whitish ooze visible when compressed. To investigate the disease aetiology, 12 Xiancao plants from three cultivars showing typical wilting symptoms were collected from Zengcheng City of Guangdong Province in June 2010. Twenty-seven bacterial isolates showing large, elevated, and fluidal colonies with a pale red centre were isolated from the vascular tissue. BLAST search against the current version of GenBank database showed 100% similarity with the 16S rDNA sequences of 26 R. solanacearum strains. This is thought to be the first report of a disease caused by R. solanacearum on M. chinensis.