Studies of the root nodules of leguminous plants IV: Production of indole acetic acid by a bradyrhizobium sp. from the root nodules of a leguminous shrub,crotalaria retusa L

Bradyrhizobium sp. isolated from the root nodules of a leguminous shrub, Crotalaria retusa L., produced a high amount of indole acetic acid (IAA) from tryptophan in the culture. The bacteria preferred D-isomer to the DL- or L-isomer of tryptophan for the IAA production. The IAA production could be increased up to 153.6% over control by supplementing the medium with arabinose (0.5%), ZnSO₄(0.01 μg/ml), KNO₃ (0.1%), thiamine-HCl (0.01 μg/ml) and EDTA (5 μg/ml). The possible role of the rhizobial production of IAA with the rhizobia-legume symbiosis is discussed.