Isolation and phytotoxicity of a metabolite from Curvularia eragrostidis and characterisation of its modes of action
2008
Jiang, S.-J. | Qiang, S. | Zhu, Y.-Z. | Dong, Y.-F.
Digitaria sanguinalis is a widespread troublesome weed distributed all over the world. Curvularia eragrostidis QZ-2000 is a potential candidate for biocontrol of D. sanguinalis. A phytotoxic metabolite from the culture filtrate of this fungus was extracted by ethyl acetate, isolated by bioassay-guided column chromatography and thin layer chromatography on silica gel, characterised by ultra violet, infrared ray (IR), mass spectrometry (MS), ¹H-nuclear magnetic resonance (NMR) and ¹³C-NMR spectral data analyses and identified as α,β-dehydrocurvularin. The phytotoxin significantly inhibited seed germination of D. sanguinalis from 43 to 688 μM. The EC₅₀ value of seed germination was 152 μM. The EC₅₀ values of elongation of radicle and coleoptile were 102 and 172 μM, respectively. α,β-dehydrocurvularin caused extensive necrosis on leaves of many notorious weeds at 688 μM, while maize and soybean were insensitive to it. Therefore, α,β-dehydrocurvularin was regarded as a non-host-selective phytotoxin. At concentrations of 172-688 μM, α,β-dehydrocurvularin caused a decrease in chlorophyll content. α,β-dehydrocurvularin had stronger impacts on chlorophyll A fluorescence, photophosphorylation and Mg²⁺-ATPase activity at higher concentrations. These results suggest that α,β-dehydrocurvularin affected the photosynthetic capacity. In the present study, α,β-dehydrocurvularin significantly inhibited mitosis of root tip cells. It supports that the α,β-dehydrocurvularin has potential for development as a natural bioherbicide.
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