The Potential Allelopathic Effects of Varthemia iphionoides and the Identification of Phenolic Allelochemicals

The allelopathic effects of aqueous extracts from Varthemia iphionoides (Compositae) leaves were tested on germination and early seedling growth of wheat (Triticum durum Desf.), barley (Hordeum vulgare L.), chickpea (Cicer arietinum L.), lentil (Lens culinaris Medik.), tomato (Solanum lycopersicum L.), and pepper (Capsicum annuum L.). The experiments were conducted in petri dishes and treatments were arranged in a completely randomized design with eight replications. V. iphionoides aqueous extract was applied in 1.25, 2.5, 5.0 and 10% concentrations and water was used as a control. Germination was observed daily and, after 7 days, radicals length and seedlings dry weight were recorded. Total germination percentage, germination rate, seedling vigor index, and seedling dry weights were significantly inhibited by V. iphionoides aqueous extracts. The germination percentage of chickpea seeds was almost unaffected by the treatment. The extract enhanced germination and seedling dry weights in chickpea at the lowest extract concentration. Tomato and wheat were the most sensitive to V. iphionoides extract followed by pepper and barley. On the other hand, chickpea and lentil were less affected. Using LC-ESI-MS/MS analysis, ten phenolic compounds were identified in V. iphionoides leaves. The results of the current study suggested that V. iphionoides aqueous extract possesses allelopathic properties and extract activities are species-specific and concentration-dependent.