To detect the potential influence of siderophores produced by Pseudomonas fluorescens on control of pathogens viz. Rhizoctonia oryzae and Rhizoctonia solani causing Sheath blight of paddy and Black scurf of potato respectively and impacts of cultural conditions on growth and siderophore production, P. fluorescens strains were isolated from various were isolated from various rhizospheric soils, identified by biochemical assays, and cultured in King B medium and these tested positive for siderophore production. The succinate medium, supplemented with 10 µM iron, was employed to study the effect of iron on siderophore production. Maximum catechol-type siderophore production at pH=7 was obtained by ML-I (88.6 µg/ml) and hydroxamate by SH-IV (15.6 µg/ml) while growth in terms of optical density by BM-II (OD600nm 1.84). The effects of pH (5-9) and time (0-24 hrs) were also studied. Among the carbon and nitrogen sources, glucose (0.4%) and L-Lysine and L-Arginine (0.1%) were found to increase siderophore production as well as growth. Dual culturing of the isolates also proved to be an effective control measure for also showed decreased growth of R. solani (upto 56.17%) and R. oryzae (upto 56.17%). The siderophore producing microbes can be used in association with a variety of crop plants to satisfy their iron thirst and help in fighting against plant pathogens.
Biocontrol, Pseudomonas fluorescens, Rhizosphere
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