Abstract
The need to reduce the use of chemical pesticides currently fosters great interest in eco-friendly biological control agents. In addition, the isolation of plant allelopathic substances and the evaluation of their phytotoxic effects can lead to the discovery of new natural herbicides. In this context, our study aimed to assess the herbicidal activity of ten crude extracts obtained from aerial parts of Tunisian spontaneous plants against Trifolium incarnatum, Silybum marianum and Phalaris minor. It confirmed that the Cynara cardunculus methanolic extract best inhibited weed germination and seedling growth, and caused necrosis or chlorosis. Following a bioassay-guided fractionation, five main phenolic compounds, (1) syringic acid, (2) p-coumaric acid, (3) myricitrin, (4) quercetin and (5) naringenin were identified in the most active crude methanolic extract. Then, only 3 of the flavonoids contained in the most active fraction were tested on Trifolium incarnatum. The 3 compounds had a significant phytotoxic effect and therefore could be employed in a new composition of botanical herbicides to control crop weeds. Besides, a novel herbicide composition was designed to improve the post-emergence activity of the methanolic extract. The formulation containing the C. cardunculus crude methanolic extract showed the same herbicidal activity as the standard industrial bioherbicide containing pelargonic acid. These results make C. cardunculus a suitable source of natural compounds potentially usable as natural herbicides.
Highlights
Weeds are registered as harmful plant pests posing a serious problem in agriculture worldwide (Suksungworn et al, 2016)
Our study aims to assess the herbicidal effect of different Tunisian plant extracts and identify the most active one, and to find out the bioactive compounds contained in that extract, so as to design a formulation based on this plant extract
The allelopathic influence on T. incarnatum, S. marianum and P. minor at 5 g/L on germination and seedling growth varied significantly depending on the plant extracts
Summary
Weeds are registered as harmful plant pests posing a serious problem in agriculture worldwide (Suksungworn et al, 2016). It can increase weed resistance to phytochemicals (Jabran et al, 2015; Ahmed et al, 2017) For these reasons, scientists are working on the identification of a biological solution that can minimize the impacts of synthetic herbicides in agricultural production (Morra et al, 2018; Sbai et al, 2016; Chengxu et al, 2011). Scientists are working on the identification of a biological solution that can minimize the impacts of synthetic herbicides in agricultural production (Morra et al, 2018; Sbai et al, 2016; Chengxu et al, 2011) This solution could offer a number of benefits such as increased target specificity and rapid degradation of the active substance (Cordeau et al, 2016)
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