Isolation and phytotoxicity of a metabolite from Curvularia eragrostidis and characterisation of its modes of action

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), 1 H‐nuclear magnetic resonance (NMR) and 13 C‐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 EC 50 value of seed germination was 152 μM. The EC 50 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 Mg 2+ ‐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.