Production of indole-3-acetic acid by berseem (Trifolium alexandrinum L.) rhizobia isolated from Haryana, India

A total of 40 Rhizobium strains were isolated from the root nodules of Berseem (Trifolium alexandrinum L.) crop which was collected from 17 different villages of three districts (Hisar, Sirsa and Karnal) of Haryana state. Morphologically, biochemically and finally by plant infectivity test, they were recognized as rhizobia. All the isolated strains were tested for the production of indole-3-acetic acid (a phytohormone having important physiological implications). IAA production was checked quantitatively in YEM (yeast extract mannitol) medium supplemented with 0.1 mgml⁻¹ L-tryptophan. All the 40 Rhizobium strains were found to be IAA producers after 72 h; however their production amount varied significantly. Rhizobium strain BH14 was found to elaborate maximum amount of IAA (176 μgml-¹) followed by BH13 (147.6 μgml-¹) and BH45 (147.4 μgml-¹). All the three superior IAA producers belonged to district Hisar. These results confirm the potential of some strains of R. leguminosarum bv trifolii as biofertilizers.