Visualization of Ralstonia solanacearum cells during biocontrol of bacterial wilt disease in tomato with Pythium oligandrum

Akira Masunaka, Kazuhiro Nakaho, Masao Sakai, Hideki Takahashi, Shigehito Takenaka

    Research output: Contribution to journalArticlepeer-review

    20 Citations (Scopus)


    The biocontrol agent Pythium oligandrum (PO) can suppress bacterial wilt caused by Ralstonia solanacearum (RS) in tomato. To understand the primary biocontrol mechanisms of bacterial wilt by PO, we pretreated tomato plants with sterile distilled water or preinoculated them with PO, followed by inoculation with RS, then observed PO and RS in fixed sections of tomato tissues using a confocal laser-scanning microscope and fluorescence labeling until 14 days after the inoculation with RS. Horizontal and vertical movement of RS bacteria was frequently observed in the xylem vessels of roots and stems of tomato plants (cv. Micro-Tom) that had not been inoculated with PO. In plants that were preinoculated with PO, the movement of RS was suppressed, and bacteria appeared to be restricted to the pit of vessels, a reaction similar to that observed in resistant rootstocks. PO colonization was mainly observed at the surfaces of taproots, the junctions between taproots and lateral roots, and the middle sections of the lateral roots. PO was not observed near wound sites or root tips where RS tended to colonize. However, RS colonization was significantly repressed at these sites in PO preinoculated plants. These observations suggest that the induction of plant defense reactions is the main mechanism for the control of tomato bacterial wilt by PO, not direct competition for infection sites.

    Original languageEnglish
    Pages (from-to)281-287
    Number of pages7
    JournalJournal of General Plant Pathology
    Issue number4
    Publication statusPublished - 2009 Jul


    • Bacterial wilt
    • Biological control
    • Confocal laser scanning microscopy
    • Micro-Tom
    • Pythium oligandrum
    • Ralstonia solanacearum

    ASJC Scopus subject areas

    • Agronomy and Crop Science
    • Plant Science


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