In vitro Biological Control of Pseudomonas viridiflava by Pseudomonas fluorescens via Siderophore Competition

Nehaya Al-Karablieh, Amani Al-Dokh, Ihsan Mutlak, Zainab Abdulhadi


Pathogenic Pseudomonas viridiflava has been recently isolated from diseased cucumber plants with fruit rotting symptoms. The pathogen is an opportunistic pathogen with wide host range, producing pyoverdins siderophores type. The aim of this study was to isolate antagonistic bacteria for P. viridiflava from phyllosphere of healthy cucumber plants. Screening for antagonistic bacteria was conducted by bacterial isolation and agar plate antagonistic assay. The potential antagonistic isolates were subjected to pathogenicity test, biochemical characterization and identification by 16S-rDNA sequencing. Among the yellowish fluorescent bacteria isolated, four isolates showed potential antagonistic activity against P. viridiflava. One selected isolate NK2 was subjected to siderophore production analysis. Biochemical characterization and identification by 16S-rDNA sequencing revealed that the isolates belonged to non- pathogenic species P. fluorescens biovar 1 group. Qualitative and quantitative analysis of siderophore production demonstrated that P. fluorescens NK2 was powerful in siderophore production which inhibited in vitro growth of P. viridiflava.


Pseudomonas fluorescens, Siderophore, LOPAT, 16S-rDNA

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