First report of bacterial blight of crucifers caused by Pseudomonas cannabina pv. alisalensis in Japan

In October 2010, a bacterial disease produced flecks and spots on leaves of Chinese cabbage, cabbage and Japanese radish in Nagano Prefecture, Japan. The symptoms started on the abaxial surface of leaves as angular, water-soaked flecks of 1–2 mm in diameter with a yellow halo of 3–4 mm width. These flecks then became visible on both leaf surfaces, enlarged and coalesced into large blight lesions. The symptoms were similar to bacterial leaf spot caused by Pseudomonas syringae pv. maculicola. The bacterium isolated from leaf lesions formed a white colony and produced polysaccharides on YP agar. The isolates were identified as P. syringae group by LOPAT tests and the 16S rDNA sequence. Moreover, the results of pathogenicity on cruciferous plants, bacteriological characteristics, rep-PCR and the sequences of rpoD and gyrB showed that the isolates should be identified as P. cannabina pv. alisalensis (recently transferred from P. syringae pv. alisalensis). This is the first report of P. cannabina pv. alisalensis isolated from diseased crucifers in Japan.