Antifeedant Activity and Contact Toxicity of the Two Peptaibols, Trichocellin A-I and B-II Isolated from the Endophytic Fungus Trichoderma reesei
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Date
2020
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Uva Wellassa University of Sri Lanka
Abstract
Plutella xylostella is a destructive cabbage pest responsible for massive economic losses
worldwide. The use of synthetic pesticides in huge amounts for its control has resulted in
pesticide-resistant strains, detrimental human health impacts, and environmental
problems. Consequently, the development of alternatives with minimal such undesirable
side-effects becomes crucial. Biopesticides derived from microbes are one such
alternative. In a preliminary study, the crude extract of the endophytic
fungus Trichoderma reesei isolated from Cyperus iria exhibited prominent antifeedant
activities against P. xylostella larvae. The main aim of the current study was to isolate the
bioactive compounds of T. reesei and investigate their antifeedant activities and contact
toxicities against P. xylostella 2nd instar larvae. Two bioactive peptaibols, trichocellin AI and trichocellin B-II, were isolated from the ethyl acetate extract of T. reesei using a
bioassay guided purification method and their structures were elucidated using nuclear
magnetic resonance and mass spectral data. To investigate the antifeedant activities
choice leaf disc assay was conducted at an initial concentration of 50µg/cm2 using
commercial neem (100%) and methanol as positive and negative controls respectively.
For contact toxicity assay larval mortality was calculated after 24 h of applying 17.5µg of
compounds/larvae. Trichocellin-A-I resulted in a 100% feeding deterrence while the
DC50 value was 2.38µg/cm2
. Trichocellin B-II also gave a feeding deterrence index of
100% for choice leaf disc assay. For the contact toxicity assay, Trichocellin A-I and B-II
showed 40% and 50% mean motility percentages respectively while the respective values
for positive and negative controls were 100% and zero. This study revealed that the
endophytic T. reesei produces two biopesticides, trichocellin A-I and trichocellin B-II,
that exhibit potent antifeedant activity and moderate contact toxicity against P.
xylostella larvae.
Keywords: Plutella xylostella, Trichoderma reesei, Choice leaf disc assay, Contact
toxicity
Description
Keywords
Agriculture, Toxicology, toxicity