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Enhanced production of indole-3-acetic acid by a genetically modified strain of Pseudomonas fluorescens CHA0 affects root growth of cucumber, but does not improve protection of the plant against Pythium root rot

Beyeler, Markus ; Keel, Christoph ; Michaux, Patrick ; Haas, Dieter

In: FEMS Microbiology Ecology, 1999, vol. 28, no. 3, p. 225-233

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    Titel
    • Enhanced production of indole-3-acetic acid by a genetically modified strain of Pseudomonas fluorescens CHA0 affects root growth of cucumber, but does not improve protection of the plant against Pythium root rot
    Autor
    • Beyeler, Markus. Laboratoire de Biologie Microbienne, Université de Lausanne, CH-1015 Lausanne, Switzerland
    • Keel, Christoph. Laboratoire de Biologie Microbienne, Université de Lausanne, CH-1015 Lausanne, Switzerland
    • Michaux, Patrick. Laboratoire de Biologie Microbienne, Université de Lausanne, CH-1015 Lausanne, Switzerland
    • Haas, Dieter. Laboratoire de Biologie Microbienne, Université de Lausanne, CH-1015 Lausanne, Switzerland
    Dokumententyp
    • Postprint
    OAI-PMH-ID
    • oai:doc.rero.ch:299849
    Summary
    The biocontrol strain CHA0 of Pseudomonas fluorescens produces small amounts of indole-3-acetic acid via the tryptophan side chain oxidase and the tryptophan transaminase pathways. A recombinant plasmid (pME3468) expressing the tryptophan monooxygenase pathway was introduced into strain CHA0; this resulted in elevated synthesis of indole-3-acetic acid in vitro, especially after addition of l-tryptophan. In natural soil, strain CHA0/pME3468 increased fresh root weight of cucumber by 17-36%, compared to the effect of strain CHA0; root colonization was about 106 cells per g of root. However, both strains gave similar protection of cucumber against Pythium ultimum. In autoclaved soil, at 6×107 cells per g of root, strain CHA0 stimulated growth of roots and shoots, whereas strain CHA0/pME3468 caused root stunting and strong reduction of plant weight. These results are in agreement with the known effects of exogenous indole-3-acetic acid on plant roots and suggest that in the system examined, indole-3-acetic acid does not contribute to the biocontrol properties of strain CHA0