Production of indole acetic acid by Enterobacter cloacea H3 isolated from Mungbean (Vigna radiata) and its potential supporting the growth of soybean seedling

Abstract

Many plant-associated bacteria synthesize the phytohormone indole acetic acid (IAA). Three bacterial isolates (H1, H2 and H3) were isolated from root nodules of Mungbean (Vigna radiata) and tested for their productivity of indole acetic acid by spectrophotometric method. Isolate H3 showed the highest IAA production (12.28 μg/ml) in culture medium supplemented with L-Tryptophan. Based on 16S rRNA gene analysis, isolate H3 was identified as Enterobacter cloacae. The cultures condition optimized for maximum IAA production by using different pH and tryptophan concentrations. IAA production of isolate H3 was maximum at pH 6 and 5 mg/ml of tryptophan concentration. The highest IAA producing isolate selected for determining its capability and compatibility to support the germination of soybean. The results showed that germination percentage and rate of soybean were not significantly different between control and isolate H3 treatment.