Pyoverdine production in pseudomonas fluorescens UTPF5 and its association with suppression of common bean damping off caused by rhizoctonia solani (kühn)

Abstract

Siderophore production is an important mechanism of biological control by a number of strains of plant growth-promoting rhizobacteria. Pseudomonas fluorescens UTPF5 was originally obtained from onion field. Biochemical and physiological characteristics of this strain refer to biovar 3 of P. fluorescens. Strain UTPF5 is an effective bacterium against several phytopathogenic fungi. Pyoverdine type siderophore of this strain was isolated using XAD amberlite column. The plant growth promotion and antifungal properties of bacteria were demonstrated under greenhouse conditions in combination with Fe-EDTA, Fe-EDDHA and Zn as modulators of pyoverdine production. Amendment with zinc, Fe-EDTA and Fe-EDDHA suppressed the disease inhibition when partially used with UTPF5. 7NSK2 and its pyoverdine mutant, MPFM1, were used as reference strains the inhibition percent of which was not affect by soil amendment. Iron chelates, especially Fe-EDDHA, increased growth and chlorophyll production by plants. This effect was improved in the presence of bacterial strains. The siderophore mutant MPFM1 did not exhibit satisfactory disease inhibition and growth promotion activity. In vitro experiments showed that purified pyoverdine could decrease the fungal growth to the same extent as pyoverdine-producing strain.