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Protection of cucumber against Pythium root rot by fluorescent pseudomonads: predominant role of induced resistance over siderophores and antibiosis
Author(s) -
Marc Ongena,
Fouad Daayf,
Philippe Jacques,
Philippe Thonart,
Nicole Benhamou,
T. C. Paulitz,
Pierre Cornélis,
Nico Koedam,
Richard R. Bélanger
Publication year - 1999
Publication title -
plant pathology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.928
H-Index - 85
eISSN - 1365-3059
pISSN - 0032-0862
DOI - 10.1046/j.1365-3059.1999.00315.x
Subject(s) - antibiosis , biology , siderophore , pythium , root rot , pythium ultimum , biological pest control , microbiology and biotechnology , botany , horticulture , bacteria , genetics
Four Pseudomonas strains were evaluated for their intrinsic properties conferring their ability to protect long English cucumber against Pythium aphanidermatum in hydroponic culture. Two of the strains, BTP1 and its siderophore‐negative mutant M3, increased plant yield as compared with the non‐inoculated control plants. Strain BTP7 was intermediate in its biocontrol activity while strain ATCC 17400 failed to reduce disease development. The role of pyoverdines could not be confirmed since treatment with either BTP1 or its siderophore‐negative mutant M3 provided similar suppression of Pythium disease. In addition, no siderophores were detected in the nutrient solution. BTP1 did not inhibit pathogen growth in vitro on several media, suggesting that antibiosis was not a mechanism of suppression. Quantification of root bacterial populations did not indicate differences among the strains. On the other hand, roots treated with either BTP1 or its sid − mutant M3 contained more antifungal phenolics than roots from any other treatments including controls. These results suggest that antifungal compounds induced by inoculation of cucumber roots with the fluorescent Pseudomonas strains BTP1 and M3 participate actively in the protection of cucumber plants against P. aphanidermatum