Rhizosphere competence of Pf-4-R, a strain of Pseudomonas fluorescens colonizing rice roots

Pseudomonas fluorescens strain Pf-4-R, inhibitory to the growth of the rice bacterial blight pathogen Xanthomonas oryzae pv. oryzae, was developed as a talc-based powder formulation. The efficacy of the formulation in sustaining the population of the Pf-4-R strain in different storage temperature was assessed. The bacterium remained viable and at optimum number for 60 days in the formulated product and storage at low temperature was more effective than room temperature. Colonization of rice roots by the strain Pf-4-R was examined by developing antibiotic rifampicin (rif) resistant mutant. Powder formulation of the mutant was prepared and seed treatment and root dip treatments were given. It was found that once introduced, bioagent was able to establish in the root zone effectively and maintained its count for whole of the crop season