Biological control of stem rot of groundnut (Arachis hypogaea L.) caused by Sclerotium rolfsii Sacc. with actinomycetes

A total of 30 isolates of actinomycetes were isolated from the rhizosphere soils of groundnut collected from different parts of Tamil Nadu, India and tested for their inhibitory activity against Sclerotium rolfsii Sacc., the stem rot pathogen of groundnut. Among the various isolates tested in vitro, five isolates (CBE, MDU, PDK, ANR and SA) were found effective in inhibiting the mycelial growth of S. rolfsii in dual culture assay. These isolates were identified as Streptomyces sp. on the basis of standard bacteriological tests and 16S ribosomal RNA gene sequence analysis. Groundnut seeds when treated with Streptomyces sp. strains showed significant increases in root length, shoot length and seedling vigour. Talc-based powder formulations of the Streptomyces sp. strains, CBE, MDU and PDK selected on the basis of their in vitro antagonism on dual plate technique and plant-growth promoting activity were prepared and tested for their efficacy in controlling stem rot of groundnut under greenhouse and field con...