title: Herbicide mixtures at high doses slow the evolution of resistance in experimentally evolving populations of Chlamydomonas reinhardtii.
abstract: The widespread evolution of resistance to herbicides is a pressing issue in global agriculture. Evolutionary principles and practices are key to the management of this threat to global food security. The application of mixtures of herbicides has been advocated as an anti-resistance strategy, without substantial empirical support for its validation. We evolved experimentally populations of the unicellular green chlorophyte, Chlamydomonas reinhardtii, to minimum inhibitory concentrations (MICs) of single-herbicide modes of action and to pair-wise and three-way mixtures between different herbicides at various total combined doses. Herbicide mixtures were most effective when each component was applied at or close to its MIC. When doses were high, increasing the number of mixture components was also effective in reducing the evolution of resistance. Employing mixtures at low combined doses did not retard resistance evolution, even accelerating the evolution of resistance to some components. At low doses, increasing the number of herbicides in the mixture tended to select for more generalist resistance (cross-resistance). Our results reinforce findings from the antibiotic resistance literature and confirm that herbicide mixtures can be very effective for resistance management, but that mixtures should only be employed where the economic and environmental context permits the applications of high combined doses.
authors: School of Life Sciences, University of Warwick, Coventry, CV4 7AL, UK.
authors: Mato
authors: M
authors: Lagator
authors: Department of Zoology, University of Oxford, Oxford, OX1 3PS, UK.
authors: Tom
authors: T
authors: Vogwill
authors: School of Life Sciences, University of Warwick, Coventry, CV4 7AL, UK.
authors: Andrew
authors: A
authors: Mead
authors: School of Biological Sciences, Institute of Evolutionary Biology, University of Edinburgh, West Mains Road, Edinburgh, EH9 3JT, UK.
authors: Nick
authors: N
authors: Colegrave
authors: School of Life Sciences, University of Warwick, Coventry, CV4 7AL, UK.
authors: Paul
authors: P
authors: Neve
mesh_terms: D001280:Atrazine / Q000008:administration & dosage / Q000494:pharmacology; D005075:Biological Evolution; D016825:Chlamydomonas reinhardtii / Q000187:drug effects* / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D005998:Glycine / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000494:pharmacology; D053209:Herbicide Resistance / Q000502:physiology*; D006540:Herbicides / Q000008:administration & dosage / Q000494:pharmacology*; D048448:Phenylcarbamates / Q000008:administration & dosage / Q000494:pharmacology; D000097797:Glyphosate
chemical_list: D001280:Atrazine; D005998:Glycine; D006540:Herbicides; D048448:Phenylcarbamates; D000097797:Glyphosate; C584522:carbetamide