Five different isolates of Pseudomonas fluorescens were isolated from rhizosphere soil of rice plant collected from different localities of Assam viz., Darrang, Jorhat, Biswanath Chariali, Titabar and Dibrugarh. These isolates were designated as Pf1 (Darrang), Pf2 (Jorhat), Pf3 (Biswanath Chariali), Pf4 (Titabar) and Pf5 (Dibrugarh) based on the place of collection. The antagonistic potential and other characteristics of the five isolates of P. fluorescens were studied in detail for colony characters, colony colour, growth type, morphology of cell, fluorescence and biochemical tests. In biochemical tests it was observed that all the isolates of P. fluorescens produced similar results with regard to oxidase test (positive), gelatin liquefaction (positive), catalase test (positive), nitrate reduction test (positive) and starch hydrolysis (negative). The fluorescent pigments produced by the isolates colleted from Dibrugarh and Jorhat were much higher than the isolates collected from other three localities. The isolates were tested for their in vitro antagonistic activity against R. solani. The isolate Pf 2 isolated from Jorhat have shown 40.66 per cent inhibition compared to control. The isolate Pf2 was found to be highly effective in reducing the sclerotia production in 88.64 per cent and the dry weight reduced in 82.72 per cent in 4 per cent MSM as compared to control may be due to the more antagonistic potential due to production of higher amount of antibiotic compounds viz., lytic enzymes, such as chitinase and β-1,3-glucanase in culture, and induced chitinase. The results offer a scope for utilizing the antagonist in organic farming also in an IDM module which managed the rice sheath blight disease.
