Investigation on the Tolerance Level of Wild Barley (Hordeum spontaneum) Populations to Clodinafop Propargyl under Greenhouse Condition

In order to study the tolerance level of different wild barley (Hordeum spontaneum) populations to Clodinafop propargyl (Topic®), a pot dose response experiment was conducted in a completely randomized design with three replications at Ferdowsi University of Mashhad Greenhouse in 2009. Cultivared barley (Hordeum vulgare) and three wild barley populations (Shiraz, Boshroyeh, and Torogh) were studied in this experiment. Also, wild oat (Avena ludoviciana) was included as a susceptible species. Clodinafop propargyl was applied postemergence at 2-3 leaf stage of plant species at different rates. Dry weight of each plant was determined three weeks after herbicide application, and then ED50, ED25, and level of tolerance index were determined for each wild barley population. Results showed that all wild barley populations were highly tolerant to herbicide even at higher doses, while wild oat was completely controlled at lower than recommended dose. ED50, and ED25 doses for wild oat was 16.3 and 5.6 g a.i ha-1, respectively, while no ED50 doses could be estimated for barley species. Based on ED25 doses, common barley showed highest tolerance to the herbicide. Tolerance level of wild barley population calculated based on ED25 of each wild barley relative to wild oat, was 29.2, 29.3, and 43.7 for Shiraz, Boshroyeh, and Torogh, respectively. It seems that all wild barley populations are highly tolerant to this herbicide, and Clodinafop propargyl can not be a solution for wild barley in wheat, while it has high efficacy on wild oat.