STUDY OF SIDEROPHORE PRODUCTION AS A MECHANISM OF ANTIFUNGAL ACTIVITY OF FLUORESCENT PSEUDOMONAS SPECIES AS BIOCONTROL ORGANISMS AGAINST FUSARIUM AND PYTHIUM SPECIESB. M. SANDIKARAbstract Among the twenty antifungal fluorescent Pseudomonas isolates obtained by primary screening, nine isolates showing potent antifungal activity (percent inhibition >50%) against the phytopathogenic Fusarium and Pythium species were selected by secondary screening using dual culture (Co-culture) method. The isolates were putatively identified on the basis of morphological, cultural and biochemical characters as Pseudomonas aeruginosa13, P. aeruginosa 58, P. putida71, P. fluorescens106, P. putida 111, P. aeruginosa 117, P. aeruginosa154, P. aeruginosa 166 and P. fluorescens171. Ability of the isolates to produce side rophores as a mechanism of antifungal activity was tested by using iron free Succinate medium (SM) and Glucose asparagines medium (GAM). The culture supernatants separated by centrifugation were tested for production of side rophores using ferric chloride and chrome azurol sulphonate (CAS) reagent. Among the nine Pseudomonas isolates tested, four isolates showed siderophore production. These siderophore producing isolates were studied for antifungal activity against phytopathogenic Fusarium and Pythium species. These isolates were also tested for 16S-r-RNA gene sequencing and confirmed as Pseudomonas aeruginosa 13, P. aeruginosa 58, P. putida 71 and P. aeruginosa 154. This study indicated that, the siderophore production is one of the important mechanisms of antifungal activity against phytopathogenic fungi. These siderophore producing Pseudomonas isolates can function as bio control agents in iron deficient soils.
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