Role of siderophore in biological control of Fusarium solani by Pseudomonas fluorescens GL20

[Synopsis] Siderophore-producing Pseudomonas fluorescens GL20 was isolated from a ginseng rhizosphere on chrome azurol S agar. P. fluorescens GL20 produced a large amount of yellow-green fluorescent pigment when it was grown in iron-deficient medium. P. fluorescens GL20 considerably inhibited spore germination and hyphal growth of Fusarium solani in dual culture. The study of antifungal mechanism with P. fluorescens GL20-S101 (Sid-), a mutant defective in siderophore synthesis, confirmed that the production of siderophore was responsible for the fungal inhibition by siderophoremediated iron (III) competition under iron-deficient conditions. In pot trials of bean with P. fluorescens GL20, disease incidence was remarkably reduced up to 94％ compared with F. solani alone and plant growth was also increased nearly 1.6 fold compared to that of the untreated control, promoting elongation and development of the roots. These results suggest that the plant growth-promoting activity of P. fluorescens GL20 can play an important role in biological control of soil-borne plant disease in a rhizosphere