Abstract
This paper aims to study the phytotoxic potential of Echinochloacolonain order to explore its potential as bioherbicide. In this way, the phytotoxic effects of the most active fraction and pure compound from methanol (MeOH) extract of E.colona shoots on germination and seedling growth of ten weed species and on E. colona itself were evaluated. A lettuce seed bioassay indicated that dichloromethane (CH2Cl2) solublefraction of MeOH extract had the most phytotoxic activity. The most phytotoxic active compound of CH2Cl2 fraction was isolated and identified as tricin. Different concentrations of CH2Cl2 fraction (100, 500, 1000 mg L-1) and tricin (50, 100, 200 µmol L-1) were used to assess their phytotoxicity on germination and seedling growth of Portulaca oleracea, Corchorus olitorius, Brachiaria reptans, Euphorbia heterophylla, Dinebra retroflexa, Hibiscus trionum, Amaranthus graecizans, Amaranthus hybridus, Convolvulus arvensis, Setaria pumila and E.colona. Low concentration of CH2Cl2 fraction (100 mg L-1) significantly stimulated germination and seedling growth of some test species. There was no significant effect of the low concentration of tricin (50µmol L-1) on germination and elongation of roots and shoots of species. Higher concentrations of CH2Cl2 fraction (500, 1000 mg L-1) and tricin (100, 200µmol L-1) inhibited germination and seedling growth of most species. The results suggest that CH2Cl2 fraction and tricin might be potentially useful as bioherbicide for weed control in agriculture.
Highlights
Allelopathy is any direct or indirect, harmful or beneficial effect that a plant or microorganism exerts on another plant by the release of chemical compounds into the environment (Rice, 1984)
The results indicated that the phytotoxic effects of E. colona on the test species are concentration–dependent
Our results agree with the findings of other studies which indicated that lower concentrations of some phytotoxic compounds can stimulate plant growth, while higher concentrations cause inhibition (Ghareib et al, 2010; Ma et al, 2011). This can be attributed to the fact that low dose of phenolic compounds stimulate protein synthesis and activation of antioxidant enzymes (Baziramakenga et al, 1995) which are effective in plant protection (Kleiner et al, 1999), while high levels of phenolic application result in plant damage (Politycka et al, 2004)
Summary
Allelopathy is any direct or indirect, harmful or beneficial effect that a plant or microorganism exerts on another plant by the release of chemical compounds into the environment (Rice, 1984) These allelochemicals are secondary metabolism products produced by plants. Weeds affect crops by competing with them for different environmental resources, as well as by the release of allelochemicals When these effects occur concomitantly, the harm caused by weeds becomes even greater. The application of synthetic herbicides reduces the amount of human labor necessary for hand weeding and controls weeds not economically or feasibly controlled by other methods They allow greater flexibility in the choice of management systems. These weeds could play effective roles for weed control instead of chemical herbicides application (Fujii, 2001), thereby reducing the risk of environmental toxicity due to application of chemical herbicides
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