Plant Growth Promotion and Biocontrol Potential of a Streptomyces sp. Strain N3-3b Isolated from the Rhizosphere of Chakhao, a Black Rice Variety of Manipur, India

Aims: To isolate and investigate actinomycete strains from rhizospheric soil of Chakhao (black rice) in Manipur, India for biocontrol and plant growth promoting activities.

Study Design: Dual culture, plant growth promoting activities and vigor index.

Place and Duration of Study: Microbial Biotechnology Research Laboratory (MBRL), Department of Biochemistry, Manipur University, India, between August 2010 and July 2013; re-analyzed and reviewed during August 2015-May 2016.

Methodology: Isolates were screened for biocontrol activity and one strain which showed significant antagonistic potential was selected for further studies. The selected strain was subjected to plant growth promoting traits such as IAA, ammonia and siderophore production, and inorganic phosphate solubilization. It was further assayed for rice seed germination and growth of rice seedlings under in vitroconditions. Characterization of the strain was also done.

Results: Among 122 putative actinomycete isolates, 9 exhibited antagonistic activity against rice fungal pathogens. N3-3b was selected as the most promising biocontrol strain for further studies. The strain exhibited plant growth promoting traits including IAA production, phosphate solubilisation and ammonia production. It promoted seed germination and significantly enhanced growth of seedlings (Vigor index) under in vitro conditions. Based on the phenotypic characteristics and 16S rRNA gene sequence analysis, the strain N3-3b was characterized as a member of the genus Streptomyces.

Conclusion: Strain N3-3b could be a potential candidate for development as bioinoculant for rice cultivation.