Isolation and characterization of Streptomyces maritimus exhibiting in-vitro and in-vivo antagonistic activity against rice blast pathogen Pyricularia oryzae

ABSTRACT A total of 178 microbial cultures were isolated from rhizospheric soil, of which 45 cultures were identified as actinomycetes based on morphology. After primary and secondary screening, the actinomycete GK-121 was found to be a potent biocontrol agent for the rice blast pathogen Pyricularia oryzae. The culture was identified using conventional microscopy, Scanning Electron Microscope (SEM) and molecular characterization of the 16S rRNA sequence, and showed 99% similarity with Streptomyces maritimus, which was further confirmed by phylogenetic analysis. The culture exhibited a 45 mm zone of inhibition during in vitro screening against P. oryzae. The greenhouse experiment further proved the effectiveness of the isolate, as the seeds treated with S. maritimus showed very low disease incidence in plants inoculated with the pathogen P. oryzae, whereas untreated seeds showed high disease incidence. This is the first report to suggest that S. maritimus is effective in controlling the rice blast pathogen, P. oryzae, in vitro and in vivo.

Keywords: Rhizosphere, Actinomycetes, Antiphytopathogenic activity, Molecular characterization, Biocontrol