EFFECT OF I.IOAGENTS AND THEIR METABOLITES ON SderoUum rolfsU Sacc.OF GROUNDNUT
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Date
2007-01-03
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University of Agricultural Sciences GKVK, Banglore
Abstract
Groundnut (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.
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