S. S. ADIVERSIDDANAGOUDA, R. RADDER2019-06-102019-06-102007-01-03TH-8369http://krishikosh.egranth.ac.in/handle/1/5810107899Groundnut (Arachis hypogaea L.) is one of the important oil seed crop of India. Stem rot caused by Sc/erotium rolfsii is a major disease constraint in groundnut production. The fungus was isolated from infected plants showing typical stem rot symptoms and bioagents Trichoderma spp. {T. harzianum, T. vinde, T. virens and T. koningii) were isolated from soil and formulated cultures by serial dilution technique. Among the six culture media tested, potato dextrose agar supported maximum growth of the Trichoderma spp. and produced maximum quantity of metabolites followed by Trichoderma specific media and Richards's agar media. T. harzianum (Dwd) isolate recorded highest biomass followed by T. harzianum (Dwd F) isolate. T. harzianum (Dwd) isolate inhibited the maximum mycelial growth of S roifsii in dual plate technique. Culture filtrates of Trichoderma spp were found effective when they were fractionated at high speed (13,000 rpm for 5 min) centrifugation than at low speed (5,000 for 15 min). Both top and bottom fractions of culture filtrates of bioagents at high speed centrifugation were on par with each other in inhibition of 5 roifsii. The inhibitiory activity effect decreased with dilution irrespective of centrifugal speed. The inhibitory activity of the culture filtrates remained unaffected even after sterilization. Thus, it indicated that the inhibitory substances to S rolfsii of bioagents are thermo stable.ennullThesis