African Journal of Microbiology Research Vol. 1 (7), 125-128, December, 2007          
ISSN 1996-0808 © 2007 Academic Journals

Rhizobium isolates from root (Sesbania procumbens) and stem nodules (S. rostrata and S. procumbens) of Sesbania species were shown to produce indole-3-acetic acid (IAA) in culture supplemented with L-tryptophan. Production of IAA was maximal after 72 h of incubation when the bacteria reached stationary phase of growth. The cultural requirements were optimized for maximum IAA production. The effect of carbon (1%) and nitrogen sources (0.1%) revealed that glucose and potassium nitrate were best promoters for IAA production over controls. The effect of different concentrations of EDTA revealed that 0.2 μgml^-1 EDTA increased IAA production. Among the three isolates, maximum amount of IAA was produced by the Rhizobium isolate from S. procumbens. The IAA from this isolate was extracted, purified and identified by thin layer chromatography.

Key words: Rhizobium species, Indole acetic acid, Sesbania species, Rhizobium-legume symbiosis.