Effects of natural herbicide from tagetes erecta on echinochloa crus-galli (L.) beauv

Abstract

We studied the inhibitory effects of leaves extracts of Tagetes erecta on weed-seed germination and the mechanisms involved. Hydroethanolic crude extract (OR) from Tagetes erecta dried leaves was partitioned into four fractions: hydrolyzed (HY), aqueous (AQ), neutral (NE) and acidic (AE). The inhibitory effects of crude extracts and its fractions were evaluated on germination and seedlings growth of Echinochloa crus-galli (L.) Beauv. The total phenolic and flavonoid contents of each fraction were also determined. Germination and seedling growth were drastically inhibited by HY and AE followed by NE, OR and AQ. The HY and AE fractions had higher concentrations of both phenolics and flavonoids than other fractions. The HY fraction was selected as most potent for development as natural herbicide due to its high yield and strong inhibitory effects. The HY fraction was formulated into a soluble concentrate product (SCT) and its inhibition potential and modes of action were investigated. The SCT drastically inhibited the seed germination of E. crus-galli, inhibiting both imbibition, α-amylase activity and also seedling growth. Cytogenetic bioassays of SCT on root-tip cells of Allium cepa L. showed that it inhibited the mitosis and thereby the cell division. It is likely that a natural herbicide may be developed from the hydrolyzed fraction of a hydroethanolic extract of Mexican marigold leaves.