Abstract:
ABSTRACT A total of 35 phosphate solubilizing bacterial strains were isolated from waste mushroom bed of Agar icus bisporus in Buyeo-Gun, Chungnam and screened for the production of indole acetic acid (IAA). The best IAA
producing strain was identified as Pantoea rodasii using 16S rRNA analysis. In addition to the IAA production, this
strain could act as an efficient phosphate solubilizer (1100 µg ml-1 after 5 days of incubation) also. The selected strain
was cultured under different conditions in order to assess the optimum conditions for maximum IAA production. The
nutrient broth (NB) medium was recorded as the best medium, where the maximum IAA production (229 µg ml-1)
was recorded at the start of stationary phase (12 hours after inoculation) of the bacteria growth. The performance
of the strain was found to be maximum at the temperature of 30o
C followed by 25o
C. IAA production was found
to be increased with increasing tryptophan concentration (from 0.1 to 0.6%), however beyond this limit, a slight reduc tion in IAA production was observed. The strains’ ability to produce IAA was further confirmed by extraction of
crude IAA and subsequent TLC analysis. A specific spot from the extracted IAA preparation was found corresponding
with the standard spot of IAA with same Rf
value. The results of HPLC analysis conducted in identifying and quan tifying the IAA production more precisely, are in agreement with the results of the assessment done with colorimetric
method. As revealed by the results of the pot experiment, the isolated strain could significantly enhance the growth
(as measured by shoot and root growth) of mung bean plants compared to that of non-inoculated plants. Therefore
it can be concluded that the present strain, Pantoea rodasii has great potential to be used as bio-inoculants
