Assessing the prospects of Streptomyces sp. RP1A-12 in managing groundnut stem rot disease caused by Sclerotium rolfsii Sacc
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Stem rot of groundnut caused by the soilborne pathogen Sclerotium rolfsii can cause significant yield losses. Biological control of stem rot using actinomycetes is a viable alternative to existing fungicidal management. Though actinomycetes are prolific antibiotic producers, reports pertaining to their use in groundnut disease management are limited. Here, actinomycetes were isolated from groundnut rhizospheric soils and screened for antagonism against S. rolfsii through a dual culture assay. Culture filtrates and crude extracts of the potential candidates were screened further for extracellular antifungal activity and characterized for biocontrol and plant-growth-promoting traits. A promising candidate was tested under greenhouse conditions as whole organism as well as crude extracts. Isolate RP1A-12 exhibited high antagonism against S. rolfsii in dual culture assay (69 % inhibition), culture filtrate assay (78–100 % inhibition at various concentrations) and crude extract assay (100 % inhibition with 1 % crude extracts). Moreover, germination of sclerotia of the test pathogen was inhibited with 1 % crude extracts. Strain RP1A-12 produced hydrogen cyanide, lipase, siderophores and indole acetic acid. Oxalic acid production by S. rolfsii was also inhibited by crude extracts of RP1A-12. In greenhouse studies, RP1A-12 reduced stem rot severity. Overall, our results suggest that isolate RP1A-12 has potential biocontrol capabilities against stem rot pathogen. Molecular characterization based on 16S rRNA gene sequencing of RP1A-12 identified it as a species of Streptomyces, closely related to S. flocculus.
KeywordsGroundnut Stem rot Biocontrol Streptomyces sp. Antifungal metabolites
The authors are thankful to Biotechnology Industry Research Assistance Council (BIRAC), A Government of India Enterprise, for providing financial support under Biotechnology Industry Partnership Programme (BIPP) scheme (Proposal No. BT/BIPP0429/11/10). The authors are also thankful to Sri Biotech Laboratories India Pvt. Ltd, Hyderabad, India for their collaboration on this project.
Compliance with ethical standards
Conflict of interest
The authors confirm that there are no conflicts of interest regarding any experimental data.
No laws have been violated while carrying out any of the experiments for this study.
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