Identification of Microflora associated with groundnuts in storage and determination of the effect of antagonistic Micro-organisms on growth andproduction of Mycotoxins

Abstract

Several micro-organisms were found to be associated with groundnuts in storage: Rhizopus spp., Fusarium equiseti, F. torulosum and F .oxysporum, Aspergillus niger, A. jlavus, A. ochraceous and A. parasiticus, Eurotium repens, Rhizoctonia spp., Sclerotium spp., Penicillium spp. and Cheatonium spp. The aflatoxigenic ones were found to be A. parasiticus, A. jlavus and Eurotium repens. Two groundnut samples out of 8 from the markets were found to contain detectable levels of aflatoxin ranging from 126.8 ppb to 436.8 ppb. The permitted total aflatoxin content in any edible sample is 20.0 ppb (Kenya Bureau of Standards )which is many times lower than what was found in the two samples. Three isolates;- Trichoderma isolate 13 (TJ3), Aspergillus niger isolate 1 and 2 were tested for their antagonism to growth of and aflatoxin production by the toxigenic strains. The antagonists Trichoderma iso.I3 and A. niger 1 were found to be effective in reducing aflatoxin production by the toxigenic strains. The greatest reduction (100%) was observed when the antagonists were inoculated into the groundnuts 2 days before these aflatoxigenic isolates. Trichoderma isolate 13 ( TJ3) was found to be less effective in reducing aflatoxin production than A. niger 1. The radial growth of the aflatoxigenic strains grown on PDA was significantly (P=0.05) reduced by T\3, A.niger 1 and A. niger 2. Trichoderma isolate 13 (TJ3) was more effective in suppressing the radial growth than the A. niger isolates. There was no significant difference in radial growth reduction by A. niger 1 and A. niger 2.