Rhizosphere competent Pseudomonas aeruginosa GRC1 produces characteristic siderophore and enhances growth of Indian mustard (Brassica campestris)

Pseudomonas aeruginosa GRC(1), an isolate of potato rhizosphere, was known to have several plant growth-promoting activities, including production of phytohormone and antibiotic substance. The isolate was found to have prolific production ability of hydroxamate siderophore in iron-deficient conditions. The siderophore of GRC(1) was purified and characterized. The purified siderophore appeared to be of pyoverdin type with typical amino acid composition. In field trials, P. aeruginosa GRC(1) enhanced the growth of Brassica campestris var Pusa Gold (Indian mustard). Significant increase in root and shoot weight, length, grain yield per plant, and total grain yield was recorded. Root colonization was studied with Tn5-induced streptomycin-resistant transconjugants of spontaneous rifampicin-resistant GRC(1) (designated GRC1(rif+strep+)) after different durations. The strain was significantly rhizopheric competent and stabilized in the rhizosphere, without disturbing the normal indigenous bacterial population.