Abstract

Rhizobacteria are possible alternative to chemical fertilizers and used to manage phyto-pathogens. In this study, rhizobacteria isolated from rice rhizosphere of coastal agriculture system of South Andaman, India were evaluated in vitro for their plant growth promoting property (PGP), antagonistic activity and genetic diversity using PCR-RFLP. From 63 isolates, 35 were positive for salt tolerance of upto 0.5 M NaCl and 27 isolates upto 1.0 M NaCl. The biochemical characterization showed that most of the isolates were positive for one or other plant growth promoting property. Antagonistic activity against the fungi Sclerotium rolfsii revealed that 13 isolates have significantly inhibited mycelial growth of S. rolfsii as compared to the control but the isolate HMI 4, HMI 5, HMI 10, HMI 14, HMI 16 and HMI 17 were most efficient in percentage inhibition of test pathogen, caused more than 35% inhibition. RFLP of 16s rDNA showed homogenous population distributed randomly at 59% similarity. 16s rDNA sequencing result showed that most predominant population were Pseudomonas spp. followed by Enterobacter and Bacillus spp. Five best isolates were evaluated in vitro for PGP activity in rice and were found promising. The present study has resulted in the isolation of PGP and antagonistic Pseudomonas (HMI 16, HMI 17) and Bacillus spp. (HMI 14) that could be useful to design strategies to use these isolates as inoculants in sustainable agriculture of Andaman, India.

Key words: Andaman, Bacillus, phosphate solubilization, PCR-RFLP, siderophore.