PRODUCTION OF INDOLE ACETIC ACID BY FLUORESCENT PSEUDOMONAS IN THE PRESENCE OF L-TRYPTOPHAN AND RICE ROOT EXUDATES

A. Karnwal

Abstract


A total of 30 fluorescent Pseudomonas isolates (15 P. fluorescens and 15 P. aeruginosa) were obtained from different plant rhizospheres and were characterized on the basis of biochemical tests and plant growth-promoting activities. Pseudomonas fluorescens AK1 and Pseudomonas aeruginosa AK2 showed the best plant growth-promoting activity. These isolates were tested for their ability to produce indole acetic acid in pure culture in the absence and presence of L-tryptophan at 50, 100, 200 and 500 µg/ml. For both strains, indole production increased with increases in tryptophan concentration (0.5, 1.2, 4.3 and 9.3 µg/ml; and 0.2, 0.7, 3.8, and 8.3 µg/ml, respectively). P. aeruginosa AK2 was less effective in production of indole acetic acid than P. fluorescens AK1. Inoculation of rice seeds with P. fluorescens AK1 and P. aeruginosa AK2 showed a good level (2.30 pmol/ml and 2.1 pmol/ml) of indole acetic acid compared to uninoculated seeds (1.6 pmol/ml).

Keywords


Plant growth promoting rhizobacteria; Pseudomonas fluorescens; Pseudomonas aeruginosa; biochemical test; PGPR activity

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DOI: http://dx.doi.org/10.4454/jpp.v91i1.624

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