Plant growth promotion inOryza sativabyBradyrhizobium sp.isolated from the rhizosphere ofAeschynomene indica

Abstract

Aeschynomene indicais traditionally used as green manure in Tamil Nadu, India, to cultivateOryza sativa. This plant containsBradyrhizobium sp. in its root and stem nodules as PGPR. In this work, we isolatedBradyrhizobium sp.from the root nodules ofA. indicausing a selective medium and used it as a biofertilizer forO. sativa. The isolated microorganism was confirmed by various biochemical tests of Bergey’s Manual. Plant growth activity was measured in terms of plant height, plant diameter, leaf width, leaf length, grain weight, soil nitrogen fixation and nutritional value of the grains. Growth promotion of isolatedBradyrhizobium sp. was compared with commercial NPK fertilizers and commercialRhizobiumliquid fertilizer. Plants treated withBradyrhizobium sp.provided a yield of 37.2 grams with average weight of 0.0182 g/grain while NPK treated plants had 38.4 g with average weight of 0.0175 g/grain. Total nitrogen fixed byBradyrhizobium sp.(192 kb/ha) is almost similar to that of commercial NPK fertilizer (196 kg/ha). The nutritional value of the grains produced byBradyrhizobiumtreatment (302 kcal) is higher than that of NPK fertilizer (286.12 kcal). Thus, free-livingBradyrhizobium sp.can be used as a biofertilizer for crops which does not have nodulation capability.