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An easy, rapid method has been needed to test the pathogenicity of strains of Ralstonia pseudosolanacearum, the cause of serious bacterial wilt on ginger (Zingiber officinale). When ginger leaves were clip-inoculated with race 4 strains, yellowing and V-shaped lesions developed on leaves, but no lesions formed after inoculation with race 1 strain or on mock-inoculated leaves. Tests of different bacterial concentrations as inoculum showed that the optimal concentration was greater than or equal to 106 cfu/ml. This simple, high-throughput leaf clipping inoculation method provides an efficient, easy method to evaluate pathogenicity of R. pseudosolanacearum race 4 on ginger.

Here, we report the complete genome sequences of three Ralstonia solanacearum strains isolated from Zingiberaceae plants in Japan. The total genome sizes of these strains ranged from 5.87 to 6.05 Mb. Strains MAFF 211472, MAFF 211479, and MAFF 311693 each carried one chromosome and one megaplasmid. MAFF 311693 contained an additional 71.9-kb plasmid.

Seventy strains of Ralstonia solanacearum from solanaceous crops in Myanmar were molecularly characterized by rep-PCR DNA fingerprinting. Cluster analysis based on the fingerprints (total 33 fingerprint types) revealed seven main clusters at 80% similarity level. Strains in phylotype I showed 29 fingerprint types and were divided into six clusters, most of which were closely correlated with host plant, geographic origin, sequevar and/or biovar. In contrast, phylotype II strains showed four DNA fingerprint types within a single cluster. These results suggest that genetic diversity of the strains is endemic and that phylotype I and II may be invasive strains.