Native isolates of groundnut stem rot causal organism, SclerotiumrolfsiiSacc. were
collected from major groundnut growing areas of Tamil Nadu. Selected isolates were screened,
characterized and identified the virulent isolates. Several native bacterial and fungal antagonists
were isolated against SclerotiumrolfsiiSacc.Two antagonistic actinomycetes isolates were found
to have antagonistic effects the groundnut stem rot pathogen. Morphology and spore structure of
isolated antagonists were studied under light microscopy, Biochemical test, Thin layer
chromatography. and Biolog analysis. It confirmed the group of microorganisms as
Streptomyces. The genus and species level of the antagonists were identified by Fatty Acids
Methyl Esters (FAME) Analysis. The antagonistic activities of S. violaceusniger were found to
be effective in reducing the mycelial growth, sclerotial formation, and sclerotial germination.
When antagonists were combined together in various combinations with each other in pot
experiments the treatment containing, seed treatment of P. fluorescens@ 5g kg -1 +S.
violaceusniger @ 5 g/kg was found to be effective in reducing the disease by 81.84 per cent over
control followed by the seed treatment of S. violaceusniger @10 g/kg (75.06 per cent).This study
provides a theoretical and practical explanation of an antagonist explored for control of stem rot
caused by S. rolfsii.