Isolation and identification of natural herbicidal compound from a plant pathogenic fungus, drechslera biseptata

Weeds incur heavy losses in crop production. Use of agrochemicals is wide spread in weed management all over the world but all of these agrochemicals are associated with numerous undesired side effects. In recent years, there is emerging trend of exploring natural herbicides from plants and microbes. In this study, phytotoxic metabolites produced by phytopathogenic fungus Drechslera biseptata (Sacc. & Roum.) Richardson & Fraser were investigated for their herbicidal activity against Rumex dentatus L., a cosmopolitan noxious weed that causes enormous yield losses in different wheat varieties. For this aim, extracts (Ethanolic extract and partitioned ethanolic extracts), chromatographic fractions and main secondary metabolite, obtained from culture of D. biseptata were tested on R. dentatus. A phytotoxic pure compound was identified as di-(2-ethyl-hexyl)-phthalate (DEHP), by spectroscopic techniques [Mass Spectrometry (MS) and Nuclear Magnetic Resonance Spectrometry (NMR)]. In leaf disk assay, DEHP at 0.5 μg μL-1 produced necrosis on weed but not on wheat leaves. On the other hand, synthetic herbicidal compound, 2,4-dichlorophenoxyacetic acid, used as positive control, produced necrotic spots at leaf discs of R. dentatus at concentration of 0.25 μg μL-1. The present investigation suggests the use of DEHP as natural herbicidal compound.