Identification and characterization of Pseudomonas fluorescensstrains effective against Xanthomonasoryzaepv. oryzae causing bacterial blight of rice in Punjab, India
For the control of bacterial blight of rice caused by Xanthomonasoryzaepv. oryzae, sixty four Pseudomonas fluorescens strains were recovered from rice and wheat rhizosphere. These strains were identified on the basis of internal transcribed spacer (ITS) region. It was observed that the strains showing fluorescence in the selective media showed the amplification of the targeted P. fluorescens specific ITS region. The strains were also characterized for the production of the antibiotic 2, 4-diacetylphloroglucinol (DAPG) using phlDlocus. The characteristic 750bp region was amplified in all the DAPG producing strains. These strains were evaluated against X. oryzae in vitro by dual culture method. The P. fluorescens strains found effective in vitro were further tested in field for their antagonistic potentiality and disease suppression ability. P. fluorescens strain number Pf-4-R showed maximum inhibition i.e. of 5.5 mm against the test pathogen X. oryzaepv. oryzae. Talc based powder formulation of the effective strain Pf-4-R used for field evaluation, showed that pre-inoculation foliar sprays were effective in controlling bacterial blight of rice with disease suppression efficiency ranging from 29.6 to 65.6 percent in different treatments.