Diversity and activity of biosurfactant-producing Pseudomonas in the rhizosphere of black pepper in Vietnam.
OBJECTIVE
Phytophthora capsici is a major pathogen of black pepper and zoospores play an important role in the infection process. Fluorescent pseudomonads that produce biosurfactants with zoosporicidal activities were isolated from the black pepper rhizosphere in Vietnam, and their genotypic diversity and potential to control Phy. capsici root rot was determined.


METHODS
Biosurfactant-producing pseudomonads were genotypically and biochemically characterized by BOX-polymerase chain reaction (PCR), 16S-rDNA sequencing, reverse-phase-high-performance liquid chromatography and liquid chromatography-mass spectrometry analyses.


RESULTS
Biosurfactant-producing fluorescent pseudomonads make up c. 1.3% of the culturable Pseudomonas population in the rhizosphere of black pepper. Although BOX-PCR revealed substantial genotypic diversity, the isolates were shown to produce the same biosurfactants and were all identified as Pseudomonas putida. When applied to black pepper stem cuttings, several of the biosurfactant-producing strains provided significant disease control. In absence of the disease, several of the bacterial strains promoted shoot and root growth of black pepper stem cuttings.


CONCLUSIONS
Biosurfactant-producing pseudomonads indigenous to the rhizosphere of black pepper plants are genotypically diverse and provide a novel resource for the control of Phy. capsici root rot and growth promotion of black pepper stem cuttings.


CONCLUSIONS
The results of this study provide a strong basis for further development of supplementary strategies with antagonistic bacteria to control foot and root rot of black pepper and to promote plant growth.
Tran
H
H
Laboratory of Phytopathology, Wageningen University, The Netherlands.
Kruijt
M
M
Raaijmakers
J M
JM
D010572:Pest Control, Biological; D010838:Phytophthora / Q000187:drug effects; D029222:Piper nigrum / Q000254:growth & development / Q000382:microbiology*; D010935:Plant Diseases / Q000382:microbiology; D018517:Plant Roots / Q000382:microbiology; D016958:Pseudomonas putida / Q000378:metabolism / Q000502:physiology*; D012988:Soil Microbiology; D013170:Spores; D013501:Surface-Active Agents / Q000378:metabolism* / Q000494:pharmacology; D014744:Vietnam
D013501:Surface-Active Agents