Biological control of ground nut stem rot fungus, Sclerotium rolfsii (Sacc.) by Streptomyces Violaceusniger along with organic ammendments

Abstract

Native isolates of groundnut stem rot casual organism, Sclerotium rolfsii Sacc. were collected from major groundnut growing areas of Tamil Nadu. Selected isolates were screened, characterized and identified the virulent isolate. Several native bacterial and fungal antagonists were isolated against Sclerotium rolfsii Sacc. Two antagonistic actinomycetes isolates were found to have antagonistic effects on ground nut 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 microorganism as Streptomyces based on gram staining, medium specific growth, visual morphological characters, cell wall aminoacid studies and spore forming characters. 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. The S. violaceusniger treated cultures were shown reduced mycelial growth (85.00%) and reduced sclerotial production (87.86%).The antimicrobial components of S. violaceusniger were also found to be inhibited the growth activities of the pathogen. One bacterial and one fungal isolate viz., Pseudomonas fluorescence and Trichoderma viride was also identified, the fungal antagonist was also found to have on par results with S. violaceusniger. When antagonists and organic amendments were combined together in various combinations with each other in pot experiments and field trial 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 theoritical and practical explanation of an antagonist explored for control of stem rot caused by S. rolfsii.