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Abstract Acidovorax citrulli (Ac) is the causal agent of bacterial fruit blotch (BFB), a disease affecting watermelon, melon and other cucurbits. A transposon (Tn5) mutant library was constructed with strain xjL12. The mutant △xj48 was selected for its loss of pathogenicity on hami melon (Cucumis melo var. saccharinus) seedlings and its ability to elicit hypersensitive reaction (HR) on tobacco. The gene disrupted by Tn5 was identified as a homolog of the hpaP gene, a conserved gene of type Ⅲ secretion system (T3SS). Further characterization of the mutant using genetic recombination revealed that swimming motility, biofilm formation and the expression of the hrcV gene requires a functional hpaP gene. Pathogenicity was partially recovered in a hpaP complemented strain. The genetic evidence in this report demonstrates that the hpaP gene is critical for the pathogenicity of Acidovorax citrulli, and plays an important role in infection.
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Received: 27 December 2010
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