December
2000
, Volume
13
, Number
12
Pages
1,340
-
1,345
Authors
Thomas F. C.
Chin-A-Woeng
,
Guido V.
Bloemberg
,
Ine H. M.
Mulders
,
Linda C.
Dekkers
,
and
Ben J. J.
Lugtenberg
Affiliations
Leiden University, Institute of Molecular Plant Sciences, Clusius Laboratory, Wassenaarseweg 64, 2333 AL Leiden, The Netherlands
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RelatedArticle
Accepted 12 August 2000.
Abstract
The phenazine-1-carboxamide-producing bacterium Pseudomonas chlororaphis PCL1391 controls tomato foot and root rot caused by Fusarium oxysporum f. sp. radicis-lycopersici. To test whether root colonization is required for biocontrol, mutants impaired in the known colonization traits motility, prototrophy for amino acids, or production of the site-specific recombinase, Sss/XerC were tested for their root tip colonization and biocontrol abilities. Upon tomato seedling inoculation, colonization mutants of strain PCL1391 were impaired in root tip colonization in a gnotobiotic sand system and in potting soil. In addition, all mutants were impaired in their ability to control tomato foot and root rot, despite the fact that they produce wild-type levels of phenazine-1-carboxamide, the antifungal metabolite previously shown to be required for biocontrol. These results show, for what we believe to be the first time, that root colonization plays a crucial role in biocontrol, presumably by providing a delivery system for antifungal metabolites. The ability to colonize and produce phenazine-1-carboxamide is essential for control of F. oxysporum f. sp. radicis-lycopersici. Furthermore, there is a notable overlap of traits identified as being important for colonization of the rhizosphere and animal tissues.
JnArticleKeywords
Additional keywords:
phenazines,
root rot,
site-specific recombinase,
sss gene.
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ArticleCopyright
© 2000 The American Phytopathological Society