Isolation of potential phototrophic purple non-sulphur bacteria in paddy and their effects on paddy seedlings in hydroponic culture

In order to promote the growth of photosynthetic bacteria (PB) use as biofertilizers in paddy fields, this study conducted during 2011 to 2012 at Department of Agricultural Microbiology, University of Agricultural Sciences, Dharwad, Karnataka, India. Twenty phototrophic purple non-sulphur bacterial (PPNSB) isolates were isolated from paddy rhizosphere soils of Northern Karnataka. Isolates were tested by morphologically, biochemically and physiologically according in to Bergey’s manual. All the isolates belong to PPNSB Rhodobacter sp. In vitro nitrogen fixation was estimated by percent nitrogen content in cells which were grown on nitrogen free culture broth. Maximum percent nitrogen content was recorded in culture broth inoculated with isolate NKPRSR -1 (2.50%). Based on percent nitrogen content, the best five efficient isolates were selected for hydroponic culture to see the effect on paddy seedlings growth under laboratory condition. In hydroponics Complete Randomized Design was used to accommodate 13 treatments with 5 replication, with the combination of nitrogen source and without nitrogen sources. Results revealed that treatment having isolate Rhodobacter sp. NKPRSR 1+ Nitrogen source show maximum plant height (26.67 cm), root length (13.17 cm), dry weight (16.50 mg/ plant) and percent nitrogen content (0.99%) after 30 days of sowing.