Effect of plant essential oils and biocontrol agents on infection of groundnut by Aspergillus flavus


Abstract: Aspergillus flavus is a major pathogen of groundnut in many countries, includingNigeria. Infection can result in contamination of groundnut seed with the mycotoxin, aflatoxin,which poses a potent threat to the health of individually consuming infected nuts. In preliminaryexperiments twelve plant oils were screened for inhibition of A. flavus on amended PDA plates.Only four extacts; clove, camphor, garlic, and galangal oils showed high inhibitory effects. Cloveoil and camphor oil also significantly suppressed infection of groundnuts by A. flavus in amendedcompost, when applied as seed treatments. Biological control based on use of Trichoderma spp.(T. harzianum, T. viride and T. asperellum), Bacillus amyloliquifaciens (isolates MBI 600, 62Pand 66P) and Pseudomonas chlorophis was also evaluated. In vitro assays on agar plates showedthe Trichoderma spp. and Bacillus isolates 62P and 66P were the most active. These sameorganisms were also effective in improving emergence when applied as a seed amendment toseed sown in Aspergillus-inoculated compost. When applied as a preventative treatment togroundnut pods, the Trichoderma spp. were also effective in suppressing infection, when thepods were subsequently inoculated with A. flavus. A strategy may be therefore be possible whichprovides control of A. flavus on groundnut, using BCAs and plant extracts, applied alone or incombination.

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